Buffer Solutions

Introduction

            Any solution that contains both a weak acid HA and its conjugate base A– in significant amounts is a buffer solution.  A buffer is a solution that will tend to maintain its pH when small amounts of either acid or base are added to it.  Buffer solutions can be made to maintain almost any pH, depending on the acid-base pair used.  The pH of a buffer solution is determined by the Ka of the acid and by the ratio of concentrations of HA and A–.  This can be calculated by rearranging the expression for the Ka of the conjugate acid of the buffer:

                                      

The rearranged equation shows that the H3O+ ion concentration of the buffer solution can be found by multiplying the Ka of the acid by the ratio of the molar concentrations of the two components.  To solve directly for the pH of the buffer, the equation can be put into logarithmic form. If the above equation is rearranged and the negative log of both sides is taken, a new form of the equation known as the Henderson-Hasselbalch equation results.

                                     

           Henderson-Hasselbalch equation


A buffer solution can maintain its approximate pH when an acid or a base is added to it because it can react with both acids and bases. If a strong acid (H3O+) is added, the basic component of the buffer (A–) can react with it, and if a strong base (OH–) is added, the acidic component of the buffer (HA) will react with it.

            H3O+ (aq)  +  A– (aq)    ¾®   HA (aq)  +  H2O (l)

            OH– (aq)    +  HA (aq)   ¾®  H2O (l)   +   A– (aq)

In this way, any strong acid or strong base that is added to the buffer solution is converted into a weak acid or weak base.  The ratio of weak acid to weak base changes, which causes the pH to change slightly, but not drastically.

            Buffer solutions are most effective when both components, the conjugate acid and the conjugate base, are present in reasonably large concentrations.  If this is the case, the buffer is said to have a high buffer capacity.  Also, a buffer is most effective when there are approximately equal concentrations of the two buffer components (a ratio of [X–]/[HX] close to 1/1) because in this case the solution will guard against large pH changes equally well whether acid is added or base is added.

In order for the solution to be considered a buffer, this ratio must be between a 1/10 and a 10/1 ratio of [X-]/[HX].  This restriction means that the [H3O+] in the buffer will be within a factor of 10 of the Ka value of the conjugate acid. It also means that the pH of the buffer will be within one pH unit of the value of the pKa of the conjugate acid.  For example, suppose you wanted to make a buffer containing phosphoric acid (H3PO4) and dihydrogen phosphate (H2PO4–).  Since the Ka of H3PO4 is 7.5 ´ 10-3 and the pKa is 2.12, as shown in the table below, the pH of this buffer would have to be between 1.12 and 3.12.  If you wanted to make a buffer with a pH outside of this range, you would have to choose a different conjugate acid-base pair.

Buffer Solutions That Can Be Made With H3PO4 and H2PO4–

Ka	pKa
7.5 ´ 10–3	2.12	1/10	7.5 ´ 10–2	1.12
		1/1	7.5 ´ 10–3	2.12
		10/1	7.5 ´ 10–4	3.12

            In this experiment, you will be assigned a pH value, and you will prepare a buffer solution having that pH. There will be two sets of acid-base pairs available in the lab. These are:

1.      Acetic acid (CH3CO2H, Ka = 1.8 ´ 10–5) and sodium acetate (NaC2H3O2).

2.      Ammonium chloride (NH4Cl, Ka for NH4+ = 5.6 ´ 10–10) and ammonia (NH3).

The buffer will be prepared by choosing the appropriate acid-base pair, calculating the molar ratio of acid to base that will produce the assigned pH, and then mixing the calculated amounts of the two compounds with enough deionized water to make 200. mL of buffer solution.

            A solution with approximately the same pH as the buffer solution will be prepared by diluting a solution of a strong acid or a strong base.  This solution will not be a buffer solution, as can be shown by comparing its buffering ability to that of the buffer solution.  Finally, a known amount of strong acid or base will be added to the buffer solution.  Before adding this acid or base, the pH change that the addition should cause will be calculated.  The observed pH change will be compared to the calculated value.

Experimental Procedure

SAFETY PRECAUTIONS:  Wear your SAFETY GOGGLES.  Use the concentrated acetic acid and ammonia solutions in the FUME HOOD.  If any acid or base solution splashes on your skin, wash it off immediately with copious amounts of running water.

WASTE DISPOSAL:  All waste from this experiment should be poured down the drain, followed by plenty of running water.

Part 1 - Preparing the Buffer Solution

Prelab Calculations

1.      Obtain a pH assignment from your instructor.

2.      Decide which of the two available buffer systems you should use.

3.      Determine the ratio of [A–]/[HA] needed in the buffer.

4.      Which component will be more concentrated, A– or HA?  Choose a value for the concentration of that component anywhere in the range 0.2 – 0.6 M. Calculate what the concentration of the other component should be.

5.      Calculate the volume (in mL) of 17.5 M CH3CO2H or 14.8 M NH3 needed to make 200 mL of your buffer.  Calculate the mass (in g) of solid NaCH3CO2·3H2O or NH4Cl needed to make 200 mL of your buffer.

Procedure

            Measure out the amounts of the buffer components needed, add them to about 100 mL of deionized water in a 250-mL Erlenmeyer flask.  Swirl until all the solids are dissolved.  Pour the mixture into a large graduated cylinder, and dilute it to a total volume of 200 mL.  Pour it back and forth between the graduated cylinder and your flask so that it is thoroughly mixed.  Store the buffer solution in the flask.

Set up a pH meter at your desk and calibrate it according to the instructions.  Remember that the electrode of the pH meter is FRAGILE!  Also, remember to rinse the electrode off with deionized water when transferring it between different solutions.

            Pour about 50 mL of your buffer solution into a small beaker and measure the pH. The pH of the solution should be close to the expected value but might not be exactly the same.  A minor discrepancy will not affect the results of the remainder of the experiment.

            There are several possible reasons for the pH meter reading being different from the expected pH.  One is that some of the volatile component of your buffer may have escaped from the solution into the air.  Another is the fact that the Ka values for acids vary with temperature.  The values usually reported are accurate for 25°C.

Part 2- Preparing a Solution with the Same pH by Dilution of a Strong Acid or Base

The pH of a typical acetic acid-acetate buffer solution is between 4 and 5.  A solution with a pH in this range can easily be prepared by diluting a solution of strong acid, such as HCl, until the hydronium ion concentration is between 10–4 and 10–5 M.  Similarly, a typical ammonium ion-ammonia buffer solution has a pH between 9 and 10.  A dilute solution of NaOH with [OH–] between 10–4 and 10–5 M will also be in this pH range.  These solutions, however will not act as buffer solutions.  In this section of the experiment, you will prepare a solution with approximately the same pH as your buffer solution by diluting a more concentrated solution of strong acid or base.

Prelab Calculations

If your buffer is acidic, calculate the volume (in mL) of 0.0010 M HCl needed to prepare 100 mL of a solution that has the same pH as your buffer.

If your buffer is basic, calculate the volume (in mL) of 0.0010 M NaOH needed to prepare 100 mL of a solution that has the same pH as your buffer.

Procedure

Prepare your unbuffered solution, by diluting the calculated amount of 0.0010 M HCl or 0.0010 M NaOH solution to a final volume of 100 mL.  Measure its pH.  Again, the reading on the pH meter may not display the pH expected for the solution.  The pH of solutions as dilute as this can be affected by small amounts of impurities, including CO2 dissolved in the water.  The pH can be adjusted if desired, but the comparison of this solution to the buffer solution will work even if the pH values of the two are not the same.

Part 3 - Comparing the Buffering Abilities of the two Solutions

Procedure

            To test the buffering abilities of the solutions, 0.1 M HCl or 0.1 M NaOH will be added.  If the solutions are acidic, add 0.1 M NaOH, and if they are basic, add 0.1 M HCl.

            Place the pH electrode in the 50 mL of buffer solution tested earlier.  Re-measure the pH, then add 5 drops of 0.1 M NaOH or 0.1 M HCl solution (see above).  Carefully swirl the solution, making sure not to bump the electrode, and record the new pH.  Repeat the procedure with another 5 drops of NaOH or HCl.  How much did the pH change upon the addition of these amounts of HCl or NaOH?

            Rinse off the electrode with deionized water, place it in the nonbuffered solution, and measure the pH.  Follow the same procedure as you used for the buffer solution.  Add 5 drops of drops of HCl or NaOH, and record the new pH.  Add 5 more drops, and record the pH.  It is important to follow the same procedure so that you can more accurately compare the two solutions.  How much did the pH change for the unbuffered solution?  How do the pH changes compare for the buffered and unbuffered solutions?

Part 4 - Changing the pH of a Buffer Solution

            The pH of a buffer solution does change when large amounts of strong acid or strong base are added to it.  Addition of strong acid uses up the conjugate base of the buffer, and addition of strong base uses up the conjugate acid.  The pH of the buffer changes because the ratio of conjugate acid to conjugate base has been changed.

            In this part of the experiment, enough 1.0 M HCl will be added to 100. mL of the buffer solution to react with half of the conjugate base in the solution.  The observed change in pH will be compared to the pH change expected on the basis of the prelab calculation.

Prelab Calculations

1.      How many moles of base (NH3 or C2H3O2–) are in 100 mL of the buffer solution you prepared?  What is half of this amount?  This is the number of moles of HCl that you will add to the solution.

2.      Calculate the volume (in mL) of 1.0 M HCl needed to supply this number of moles.  That is the amount needed to react with half of the conjugate base in 100 mL of your buffer solution.

3.      What should the pH be after this amount of HCl is added?  What is the expected change in pH of the buffer?

Procedure

Add this volume of 1.0 M HCl to 100 mL of  the buffer solution, and measure the pH.  Record the change in pH.  Compare the expected (calculated) pH change to the actual pH change of the buffer.

Sample Calculations

Part 1 – Preparing a Buffer Solution

Sample calculations will be done for an assigned pH of 2.50.

            A pH of 2.50 corresponds to a [H3O+] = 10–2.50 = 3.162 ´ 10–3 M.  Phosporic acid (H3PO4) and sodium dihydrogen phosphate (NaH2PO4) could be used to make this buffer, because Ka for H3PO4 (Ka = 7.5 ´ 10–3) is close to the desired [H3O+].

            The  ratio should be  =  =  =

            H2PO4– will be the most concentrated component of this buffer system.  We will arbitrarily choose its concentration to be 0.50 M.  This means that the concentration of H3PO4 should be 0.50 M ¸ 2.372 = 0.2108 M

            To make 200 mL of the buffer solution, we will need to measure out a certain volume of concentrated phosphoric acid, which is available as a 14.7 M aqueous solution.  And we will need to weigh out a certain mass of sodium dihydrogen phosphate, which is available as the hydrated solid, NaH2PO4·2H2O (the waters of hydration are included in the molar mass).

            To make 200 mL of a 0.2108 M phosphoric acid solution,

                        200 mL ´  = 2.87 mL of concentrated phosphoric acid needed.

            To make 200 mL of a 0.50 M sodium dihydrogen phosphate solution,

                        0.200 L ´  ´  = 15.60 g of NaH2PO4·2H2O needed.

            So, to prepare the buffer solution, we will mix 2.87 mL of concentrated H3PO4 and 15.60 grams of NaH2PO4·2H2O with enough water to make 200 mL of solution.

Part 2- Preparing a Solution with the Same pH by Dilution of a Strong Acid or Base

            To make 100 mL of a solution with pH = 2.50 ([H3O+] = 3.162 ´ 10–3 M), we will dilute a 0.10 M HCl solution.  (Note, in your experiment, you will be diluting an 0.0010 M HCl solution or an 0.0010 M NaOH solution.)

            100 mL ´  = 3.16 mL of 0.10 M HCl needed

            So, to prepare the unbuffered solution, we will mix 3.16 mL of 0.10 M HCl with enough water to make 100 mL of solution.

Part 4 - Changing the pH of a Buffer Solution

            We will take 100 mL of the buffer solution, and add enough 1.0 M HCl to react with half of the moles of H2PO4–, the conjugate base.

                        0.100 L ´  = 0.050 moles of H2PO4– are present in 100 mL

                        0.025 moles of H2PO4– will be react with 0.025 moles of HCl.

                        0.025 mol HCl ´  = 0.025 L or 25 mL of 1.0 M HCl will be added.

            So, to change the pH of our buffer solution, we will take 100 mL of our original buffer solution, and add 25 mL of 1.0 M HCl to it.

            All of the added HCl will react with the H2PO4–.  Some H2PO4– will be used up, and more H3PO4 will be formed.

                                          H3O+ (aq)  +  H2PO4– (aq)  ¾®  H3PO4 (aq)  +  H2O (l)

            Before reaction        0.025 mol         0.050 mol               0.021 mol              lots

                                         –0.025 mol       –0.025 mol            +0.025 mol

            After reaction          0                      0.025 mol               0.046 mol

             =  = 1.38 ´ 10–2 M

            So, after the addition of HCl, the new pH will be –log (2.01 ´ 10–2) = 1.86.  The expected change in pH will be 1.86 – 2.50 = –0.64 pH units.

Additional Questions (for the finished lab report)

1.      For each of these desired pH values, choose a weak acid-conjugate base pair from your textbook that could be used to prepare a buffer solution with that pH.  Calculate the desired [A–]/[HA] ratio in each case.

(a) pH = 6.00                  (b) pH = 8.00               (c) pH = 11.00

2.      500 mL of a buffer solution contains 0.050 mol NaHSO3 and 0.031 mol Na2SO3.

(a) What is the pH of the solution?

(b) Write the net ionic equation for the reaction that occurs when NaOH is added to this buffer.

(c) Calculate the new pH after 10. mL of 1.0 M NaOH is added to the buffer solution.

         (d) Calculate the new pH after 10. mL of 1.0 M NaOH is added to 500. mL of pure water.

(e) Explain why the pH of the water changed so much as compared to the pH of the buffer.

FILE LINKS


buffer solutions 1

buffer solutions 2

Cardiovascular drugs

Digitalis

Cardiac glycosides include digoxin, digitoxin and ouabin. These are derived from plant Foxglove (Digitalis purpurea). Cardiac glycosides composed of steroid nucleus linked to a lactone ring and a series of sugars.

Clinical uses: treatment of congestive heart failure and management of supraventricular rhythm disturbances.

Pharmacokinetics: digoxin is taken orally, well absorbed but in some patients (10%) the presence of some enteric bacteria may cause degradation of the drug and the use of broad spectrum antibiotics may cause sudden increase in serum digoxin level causing toxicity. Cardiac glycosides are widely distributed to tissues including CNS. Digoxin is excreted unchanged by the kidney; the dose should be adjusted in patients with renal impairment. Digitoxin is metabolized in the liver and excreted in bile.

Digoxin has narrow therapeutic index; the toxic dose is 2 ngm/ml which is near to the therapeutic dose which is 1.1 ngm/ml.

Cardiac effect

1-    Mechanical effect

Through inhibition of Na­⁺/K⁺ ATPase enzyme (membrane bound enzyme). This enzyme keep K⁺ inside the cell and Na­⁺ outside the cell; so when this enzyme is inhibited K­⁺ transport back into the cell is blocked and its concentration in the extracellular fluid increases, at the same time Na ions will enter the cell and this will promote or facilitate the entry of Ca ⁺² which are essential for the contraction of actin and myosine.

2-     Electrical effect  ( direct effect and autonomic effect)

a-    Direct effect

It causes brief prolongation of the action potential followed by a period of shortening especially the plateau phase. The decrease in the action potential duration is probably the result of increase potassium conductance that is caused by increase intracellular ca ions. All these effects can be observed at therapeutic concentration in the absence of over toxicity.

Shortening of the action potential contributes to the shortening of atrial and ventricular refractoriness.

At higher concentration resting membrane potential is redused (made less negative) as aresult of inhibition of sodium pump and reduced intracellular K⁺, this lead to appearance of ascillatory depolarizing afterpotential which followed normally evoked action potentials. The afterpotentials also known as delayed afterdepolarizations are associated with overloading of the intracellular Ca⁺² store.

·        When below threshold, these afterpotentials may interfere with normal conduction.

·        When afterpotential reach threshold it elicits an action potential (premature depolarization or ectopic beat).

·        If afterpotentials in the purkinje conducting system regularly reach threshold bigeminy will be recorded on the electrocardiogram (ECG).

NSR: an inverted T wave and depressed ST segment are present.

PVB: is a manifestations of depolarization evoked by delayed oscillatory afterpotential.

With further intoxication, each afterpotential evoked action potential will itself elicit a suprathreshold afterpotential, lead to tachycardia and fibrillation.

b-    Autonomic action (indirect)

Indirect action include sympathetic and parasympathetic.

At low dose parasympathomimetic effects predominate, lead to decrease heart rate, decrease conduction velocity, prolongation of refractory period so digoxin used in the treatment of supraventricular arrhythmia.

At toxic level sympathetic out flow is increased  lead to increase heart rate and contraction.

Manifestation of digitalis toxicity

1-     Gastrointestinal effect: anorexia, nausea and vomiting. They are the earliest signs of toxicity.

2-    Visual effect: blurred vision, loss of visual acuity and yellow-green halos.

3-    CNS effect: headache, fatigue and confusion.

4-    Cardiac effect: sever dysrhythmia moving from decreased or blocked atrioventricular nodal conduction, paroxysmal supraventricular tachycardia to the conversion of atrial flutter to atrial fibrillation, premature ventricular depolarization, ventricular fibrillation and finally complete heart block.

5-    Endocrinological effect: gynecomastia due to antiandrogenic effect of the drug.

Factors predisposing to digitalis toxicity

1-    Electrolyte disturbances: hypokalemia, hypomagnesemia and hypercalcemia predispose digitalis toxicity.

2-     Hypothyroidism, hypoxia, renal failure and myocarditis are predisposing factors to digitalis toxicity.

3-     Drugs: quinidine can cause digitalis intixicationboth by displacing digitalis from plasma protein binding sites and by competing with digitalis for renal excretion.

Verapamil also diplace digitalis from plasma protein binding site and can increase digoxin levels by 50-75%, this may require a reduction in the dose of digoxin.

Potassium depleting diuretics, corticosterois and a variety of drugs can also increase toxicity.

4-     Use of antibiotic lead to kill microorganisms like Eubacterium lentum so lead to toxicity.

Treatment of digitalis toxicity

1-     Removing of ingested drug by vomiting, gastric lavage, use of adsorbant agents eg. Activated charcoal, cholestyramine and colestepol.

2-     Maintenance of a normal potassium concentration: hypokalemia is more common after chronic digitalis toxicity, while massive acute overdoses often causes hyperkalemia. Potassium compete with digoxin on Na⁺/K⁺-ATPase pump so decrease K⁺ level and increase digoxin activity and toxicity.

Hyperkalemia may require treatment with insulin, dextrose, bicarbonate and sodium polystyrene sulfonate. In case of hypokalemia continuous potassium replacement may be sufficient. Potassium administration may correct arrhythmias restoring intracellular concentration.

3-     Reversal of arrhythmias: for atrial and ventricular arrhythmias that do not respond to potassium therapy the treatment of choice includes phenytoin and lidocaine. Phenytoin increase AV nodal conduction and directly reverse the toxic action of digitalis at AV node without interfering with its inotropic action. While quinidine and procainamide are not used because they slow AV nodal conduction.

If digitalis has produced AV block, the vagolytic action of atropine may increase heart rate and AV conduction. Catecholamines are contraindicated for the treatment of bradyarrhythmias because they increase the risk of precipitating more serious ectopic arrhythmias. Β-blockers such as propranolol are useful to suppress  supraventricular and ventricular arrhythmias induced by digitalis toxicity.

4-     Increase removal of unabsorbed drug: the use of dieresis or hemodialysis have not been successful because of the large volume of distribution for digitalis. Hemodialysis may be equired to control hyperkalemia.

5-     Use of specific antidote digoxin immune Fab: these are antibody fragments prepared by conjugation of digoxin to human or bovine serum albumin. This is then used to immunize sheep, which produce antibodies. Their sera are obtained and purified yielding the drug.

The fragments are less immunogenic and can be eliminated by glomerular filtration.

Adverse effects to digoxin immune Fab are minimal including

DRUG CLASSIFICATION

Acne Vulgaris Drugs

These drugs control the inflammatory eruptions composed of cysts, papules, and comedones, predomi­nantly on the face, upper back, and chest. The condition occurs in a majority of people during puberty and adolescence. Examples: Benzoyl peroxide, tretinoin, Ultra, Olux, and topical erythromycin.

Anabolic Agents

Anabolic agents are the ones, which can stimulate growth of muscle mass. They are the compounds with androgenic properties and are used in severe cases of emaciation and most prominently by athletes to increase their muscle size, strength, and endurance. Some of the examples are Histerone 100, Depo-Testosterone, Malogen, etc.

Analgesics

Analgesics or as the name suggests are drugs, which have the property of reducing the pain or rather producing a neurologic and phar­macologic state in which the painful stimuli are blunted so much so that though they are still perceived, they are no longer painful.

Antacid

Antacids are agents used to neu­tralize the excess acid in the stomach released in cases of acidity, gastritis and ulcers. They neutralize the effects of HCl, thereby providing re­lief from indigestion and heartburn. The efficacy of antacids depends on their capacity to protect the mucosa of the stomach from acid and pepsin. Drugs: Calcium carbonate.

Antiallergics

Antiallergics prevent, inhibit, and alleviate allergic reactions. Generally, histamines are responsible for allergies. Antiallergics act as antihistamines and suppress their effects. Anti­allergics act against itching and flash responses of the histamines. Antihista­mines are subdivided in two broad cat­egories: sedative and non-sedative. Cetirizine is one example of non-sedative antihistamine, while diphenhydramine and hydroxyzine are the examples of sedative antihistamines. Two lesser known categories of antihistamines are mast cell stabilizers and histamine re­ceptor blockers.

Antianginals

Antianginals act against angina pectoris, that is the symptom exhibited in ischemic heart disease. Antianginals im­prove the balance between the delivery of oxygen to myocardium and its utilization by the myocardium. Antianginals are available in various forms, viz., calcium channel blockers, organic nitrates, beta-adrenergic blockers, potassium channel acti­vators, and antiplatelet drugs. These drugs relieve angina pectoris by expand­ing blood vessels of the heart. Some are nitroglycerin, nifedipine, diltiazem, and verapamil.

Antiarrhythmics

Antiarrhythmic drugs are used to treat irregular heart rhythms resulting from the disturbance in the heart's electrical firing system. Antiarrhythmic drugs enhance the blood flow in the coronary vessels of the heart. This causes vasodila­tion and decreases the resistance felt in the peripheral vascular system. Clinically, antiarrhythmics are divided into three broad categories;

a)      Which act on supraven­tricular arrhythmia (like digoxin and verapamil).

b)      Which act on both su­praventricular and ventricular arrhythmia (quinidine, amiodarone, metoprolol)

c)      Which act solely on the ventricu­lar arrhythmia.

Anticoagulants

Anticoagulants delay the clotting or coagulation process of blood. When any vessel is blocked by a clot of blood, an anticoagulant is administered to prevent new clots from forming with the earlier clots and thereby suppressing their enlarge­ment. However, an anticoagulant only prevents from blood clotting but is incapable of dissolving an existing blood clot. Patients with artificial heart valves and atrial fibril­lation are at the risk of forming blood clots and they are therefore prescribed antico­agulants to prevent such a situation. Heparin and warfarin are the most commonly used anticoagulants.

Anticonvulsants

Anticonvulsants alleviate or reduce the severity of seizures and also pre­vent further seizure attacks.

Antidepressants

Drugs useful in treatment of depression are termed as anti-depressants. There are three kinds of antidepressants, viz., tetracyclic, triazolopyridine, and tri­cyclic.

Antidiabetics

Antidia­betic agents are drugs that lower the blood sugar level. They are therefore also called hypoglycemic drugs. They are of two types; sulfonylureas and biguanides. Examples of sulfonylureas are chlorpropamide and glipizide while Metformin and phenformin are biguanides.

Antidiarrheals

Antidiarrheals are the agents used to relieve diarrhea. They do so either by absorbing the excess fluids that cause diarrhea or by slowing the movement of fe­cal material through intestine thereby allow­ing more time for absorption of water. The first step in treatment of diarrhea is re­placement of fluid and electrolytes.

Antiemetics

Antiemetics are agents that suppress nausea and vomiting. These drugs act on brain control centers to stop nerve impulses, control motion sickness and dizziness. Antiemetics can be further divided into various categories like antihistamines, anticholinergics, and dopamine antagonists. Eg: Ondansetron is one of the strongest antiemetic.

Antiflatulents

Antiflatulents reduce gas and bloating. These agents facilitate passing out of gas by break­ing down gas bubbles into smaller size by stimulating intestinal motility. Eg: Maalox, Mylanta.

Antiglaucoma drugs

Drugs that lower the intraocular pressure of the eyes by reducing produc­tion of aqueous humor are called antiglaucoma drugs. Most drugs of this class are beta-­adrenergics. Drugs: timolol maleate, betaxolol, levobunolol, pilocarpine.

Antihistamines

Histamines cause the swelling and inflammation of the nasal passages. Antihistamine counteracts that effect. Antihistamines are the primary agents used to relieve the allergic rhinitis symptoms. Antihistamines dry the respi­ratory tract and are effective in treating the cough caused by the allergens and the common cold in its early stages.

Antihypertensives

Anti­hypertensives are the agents used to lower high blood pressure. They include diuret­ics also known as water pills, beta block­ers, alpha blockers, alpha-beta blockers, sympathetic nerve inhibitors, angiotensin converting enzyme inhibitors, and cal­cium channel blockers. Antihypertensives work one or more the following three ways to lower the blood pressures in the ves­sels, by decreasing the blood volume, restricting constriction or nar­rowing of the blood vessels and increase dilation thereby making the blood flow easier, by decreasing the force of the heart thereby decreasing the blood pumped through the arteries. Ex­amples are amlodipine, quinapril, benazepril, captopril, clonidine, enalapril, furosemide, terazosin, lisinopril, nifedipine, and quinapril.

Anti-inflammatory drugs

Are the drugs that reduce inflammation in cases of infection, injuries etc. Anti-inflamma­tory drugs are available in two types: steroidal and non‑steroidal called NSAID. Anti-inflam­matory drugs do not act directly against the causative agents. They act on the mechanisms of the body and reduce the inflammation. Non-steroidal anti-inflam­matory drugs are generally used in cases of arthritis and gout. Glucocorticoids and aspirin are the examples.

Antipsoriatic

Psoriasis refers to the circum­scribed, silvery-scaled confluent, reddish lesions of the skin that primarily occur on knees, scalp, elbow, and trunk. Drugs treating psoriasis are called antipsoriatic drugs.

Antiseborrheics

These drugs are effective for treatment of seborrheic dermatitis manifested by erythematous and scaly le­sion. Selenium sulfide, selenium disulfide with clotrimazole, cetrimide, & a combination of cetyl alcohol, sulphur precipitate, salicylic acid. Indications: Dandruff, seborrheic dermatitis.

Antispasmodics

Antispasmodics are the agents used in prevention and reduction of smooth muscle spasms by acting on the autonomic nervous system, thus relieving spasms of bowel. Eg: Belladonna alkaloids.

Antitussives

Antitussive drugs suppress cough. Codeine, dextromethorphan are some examples.

Antiulcers

Anti-ulcers are administered in the cases of peptic ulcers to get relief from pain, promote healing, and prevent recur­rence. Drugs: ranitidine, cimetidine, omeprazole, famotidine, nizatidine.

Beta-adrenergics

Beta-adrenergic blocking agents are used in the treatment of arrhythmias, stable (exercise-induced) an­gina: unstable angina, postmyocardial hypertension, and migraine headaches. Beta-blockers act like inhibitors and interfere with the action of stimulating hormones on the beta-adrenergic receptors in the nervous system. Beta-blockers are divided into the groups of beta I (affecting the heart) and beta 2 (affecting the receptors in the bronchial tissue). Atenolol and meto­prolol are the two examples of beta-adren­ergic blockers.

Bronchodilators

Bronchodilators open up the clogged lung airway passages at times of airway narrowing. They open up the breathing passages and dilate the bronchi.

Calcium Channel Blockers

Calcium chan­nel blockers are the agents that selectively block the flow of calcium ions into the cardiac and smooth muscle cells. These agents lower the blood pressure, relieve angina (chest pain), and stabilize the cer­tain types of abnormal heart rhythms. They are used to treat angina pectoris, some form of hypertension, and some arrhythmias. Diltiazem and Verapamil are such calcium channel blockers.

Contraceptives

Contraceptives inhibit ovulation and thereby acts as a deterrent against preg­nancy. They are available as steroids and chemicals. Steroids are generally the oral contraceptive pills called OCP, a combination drug of estrogen and progesterone. On the other hand, chemical contraceptives com­prise foam, gel, cream, or other spermicidals, which are placed in the va­gina before intercourse. They prevent pregnancy by killing the sperms.

Corticosteroids

Corticosteroids are steroids produced by the adrenal cortex. Corticosteroids are used for adrenal insufficiency. They suppress inflammation, allergy, and reduce the chances of rejection in transplantation cases, and also treat some tu­mors. The two kinds of corticosteroids are mineralocorticoids and glucocorticoid. Al­dosterone is an example of mineralocorti­coids. Hydrocortisone, prednisolone, and triamcinolone are glucocorticoids.

Cycloplegics and Mydriatics

Cycloplegics are agents that paralyze ciliary muscles and result in pupillary dilation. Mydriatics are agents that cause dilation of pupils. Most of the mydriatics cause cycloplegia also. Drugs: atropine, homatropine, cyclopentolate, and tropicamide.

Decongestants

Decongestants reduce the congestion of swelling in the nasal pas­sages, especially by constricting the blood vessels and limiting the blood supply to the area.

Diuretics

Diuretics increase the rate of urine formation after administration. All diuretic agents except osmotic diuretic act directly on the kidneys at the level of re­nal tubules. Diuretics are used to treat edema due to nephrotic syndrome and other diseases. Some examples are hydro­chlorothiazide, Dyazide and Dyrenium.

Emollients and Keratolytics

Emollients are agents used to soothe and hydrate the skin. After application on the skin, emol­lients prevent evaporation of water by forming a thin greasy layer on the skin surface. Emollients improve the dryness of skin but are not to be used on exuda­tive lesions, Vaseline petrolatum, oils like coconut, ground nut, etc. Keratolytics are agents applied to soften the epidermic cells and desquamate them. Salicylic acid, benzoic acid, propylene glycol, zinc oxide, and dimethicone are some of them.

Estrogen hormones

Estrogen hormones are used as oral contraceptives and also in the treatment of postmenopausal osteoporosis. They act by binding the estrogen nuclear receptors. However, prolonged use can lead to skin rash, thromboembolism, and endometrial can­cer. Estrogens are secreted by ovaries and are necessary for normal development of breasts, female genital tract, and secondary sexual characteristics. Estrogens are also necessary for maintenance of preg­nancy:

Expectorants

They help loosen the mucus by making bronchial secretions thinner and easier to cough up. Iodides are com­monly used expectorants, and guaifenesin and terpin hydrate are ingredients in many over-the-counter preparations.

Fibrinolytics

Fibrin is a kind of elastic pro­tein derived from fibrinogen, which helps in the clotting of blood. Fibrinolytics dis­solve the clots by hydrolysis of fibrin. These fibrinolytics produce plasmin en­zyme, which acts against the clotting process. Fibrinolytics are used in the treat­ment of pulmonary embolism and deep venous thrombosis.

Gonadotropin

Gonadotropins are the hor­monal preparations of follicle stimulating hormone (FSH) and luteinizing hormone (LH) that raise the sperm count in infer­tility cases. These preparations are re­quired for ovulation and spermatogenesis.

Hemostatics

Hemostasis is a condition in which bleeding is arrested and hemostat­ics are agents, which arrest the bleeding in the vessels.

Hypnotics

Hypnotics are those agents or drugs, which have soporific effect and are used for causing sleep or hypnosis.

Immunosuppressants

Immunosuppres­sants prevent or interfere with the immu­nologic response. In cases of transplants, the host tissues sometimes reject the transplanted organs or tissues. Immuno­suppressants are used to facilitate the ac­ceptance of the transplanted organs and prevent the rejection and also used in the treatment of autoimmune disease.

Laxatives

Laxatives promote bowel movements and defecation when used in small doses to relieve constipation and in large doses to evacuate the whole gastrointesti­nal tract. Drugs: cascara sagrada, casanthranol, and docusate.

Miotic

Miotic agents cause constriction of pupil of eye. Mostly used in the treatment of glaucoma. These agents are used to counteract mydriatics after they have been used for testing refraction. Drugs: pilocarpine.

Mucolytics

Mucolytics liquefy or break down the obstinate mucus so that it can be expectorated more easily.

Muscle Relaxants

Muscle relaxants are those agents, which reduce the muscle ten­sion and provide therapeutic treatment. These agents block the polysynaptic spi­nal reflexes and reduce the muscle tone. Examples: Baclofen, methocarbamol, and tizanidine.

Neuromuscular Drugs

Neuromuscular drugs are generally used during anesthe­sia administration to allow access to body cavities. They prevent the voluntary or reflex muscle movement interference. Neuromuscular drugs can be divided into three broad categories: non-depolarizing muscle relaxants, depolarizing neuromus­cular blockers, and anticholinesterases used in anesthesia.

Ophthalmic antibiotics

Various antibiot­ics are used in many eye infections caused by pathogens like bacteria. Many of these antibiotics are used in combination with corticosteroids. These antibiotics are used to treat bacterial infections of the eye, fun­gal infections of the eye, conjunctivitis, keratitis, blepharitis, meibomianitis, tra­choma, dacryocystitis and differ according to the type of infection. Drugs: norfloxacin, ciprofloxacin, gentamicin, tobramycin, sulfac­etamide sodium, chloramphenicol, miconazole, silver sulfadiazine, acyclovir, ofloxacin, framycetin sulfate, polymyxin.

Opiates

Opiates are the narcotic drugs derived from opium. There are multifarious uses of opiates. They are used as analge­sics, hypnotics, mood elevators, and antidiarrheals.

Oxytocins

Oxytocin is a nonapeptide neu­rohypophyseal hormone that causes myometrial contractions at term and promotes milk release during lactation. Oxytocins are used for induction or stimulation of labor. They are also used to manage the postpartum hemorrhage and atony

Psychotropics

Psychotropic drugs affect the mind, emotions, and behavior. They are used in the treatment of psychic illnesses.

Sedatives

Sedatives are those agents or drugs that depresses the central nervous activities and contain the excitement.

Spermicidals

Spermicidals are available in gel, pessary or foam, or in cream formula­tion. (Pessary is a surgical plug worn in the vagina to support the womb.) Spermicidals are placed in the vagina for contraception, for they destroy the sperms.

Topical Analgesics

Topical analgesics stimulate the sensory nerve endings and produce a soothing tingling sensation and warmth. Diclofenac, nimesulide, and ketoprofen are the examples of such topical analgesics.

Topical Antifungals

Topical antifungals kill the fungus selectively. These include scabicides, which kill the scabiei that in­vade the epidermis. Examples: malathion, lindane, benzyl benzoate. Some other antifungals are miconazole, which has a broad spectrum of antifungal activity and is used for fungal and eczematous infections of tinea, candidiasis of skin and nails and also for eczema with bacterial infection; clotrimazole, which is used for tinea infec­tions, fungal nappy rash, candida vulvitis, candida balanitis, paronychia, and athlete’s foot; econazole for fungal infections of skin and skin infections due to gram­ positive bacteria; and keto­conazole for fungal infections of skin.

Topical Anti-infectives

Topical anti­-infectives are used for treatment of bacte­rial infections of skin, impetigo, eczema, folliculitis, leg ulcers. Also used for abra­sions, cuts, and as preoperative antisep­tics. Examples-mupirocin, tetracycline, aminoglycoside, sulfonamides, nitrofurazone, acyclovir. The antiseptics used are chloroxylenol, cetrimide, Povi­done iodine.

Topical steroids

Topical steroids are used to treat various dermatological disorders like contact dermatitis, psoriasis, keloid scars, seborrheic dermatitis, eczema, and vulval pruritus. Examples: beclomethasone dipropionate, triamcinolone acetate, hydrocor­tisone, methyl prednisolone acetate, dexametha­sone sodium phosphate.

Tranquilizers

Tranquilizers are agents or drugs, which have a calming, soothing, or pacifying effect. This helps in the treat­ment of anxiety and agitation.

Uricosurics

Uricosurics increase the excre­tion of uric acid from the body They are generally used to treat gout. Some of the prominent uricosurics used are allopurinol (Zyloprim), colchicine (available as generic only), probenecid (Probalan), etc.

Vaccines and immunoglobulins

Vaccines and immunoglobulins are used for immunological prophylaxis. Immunization can be obtained in two ways, active and passive. Active immunization is obtained through the administration of vaccines and also by recovering from an infection and thereby building the resistance. Pas­sive immunization is obtained through the administration of antibodies by means of antiserum and immunoglobulins. Some of the well-known vaccines and immuno­globulins are as follows: BCG vaccines, polio vaccines, triple antigen, tetanus immunoglobu­lin, rabies immunoglobulin, etc.

Antiseptics and Disinfectants

Proflavine, Benzalkonium chloride, cetrimide, Formaldehyde solution, Hexachlorophene, Liquefied phenol, Nitrofurantoin. Sulfathiazole, succinyl sulfathiazole, sulfadimethoxine, sulfamethoxypyridazine. Sulfa, co-trimoxazole, sulfacetamide.

Some Common Drugs:

·        Antileprotic Drugs-clofazimine, Thiambutosine, Dapsone, solapsone.

·        Anti-tubercular Drugs-Isoniazid, PAS, Streptomycin, Rifampicin, Ethambutol, Thiacetazone, Ethionamide, Cycloserine, Pyrazinamide.

·        Anti‑amoebic and /anthelmintic Drugs-Emetine, Metronidazole, Halogenated hydroxyquinoline, diloxanide furoate, Paromomycin Piperazine, Mebendazole.

·        Antibiotics-Benzyl Penicillin, Phenoxy methyl Penicillin &, Benzathine Penicillin, Ampicillin, Cloxacillin, Carbenicillin, gentamicin, Neomycin, Erythromycin, Tetracycline, Cephalexin, Cephaloridine, Cephalothin, Griseofulvin, Chloramphenicol. Antifungal agents-Undecylenic acid, Tolnaftate, Nystatin, Amphotericin, Hamycin.

·        Antimalarial Drugs-Chloroquine, Amodiaquine, Primaquine, Proguanil, Pyrimethamine, Quinine, Trimethoprim.

·        Tranquilizers-Chlorpromazine, Prochlorperazine, Trifluoperazine, Haloperidol, Oxypertine, Chlordiazepoxide, Diazepam, Lorazepam, Meprobamate.

·        Hypnotics:- Phenobarbitone, Methyprylon, paraldehyde. Triclofos sodium.

·        General Anesthetics-Halothane, Cyclopropane, Diethyl ether, Methohexital sodium, Thiopental sodium, Trichloroethylene.

·        Antidepressant Drugs-Amitriptyline, Nortriptyline, imipramine, Phenerzine, Tranylcypromine.

·        Analeptics-Theophylline, Caffeine, Dextro-amphetamine.

·        Adrenergic Drugs-Adrenaline, Noradrenaline, Isoprenaline, Phenylephrine, Salbutamol, Terbutaline, Ephedrine, Pseudo ephedrine.

·        Adrenergic Antagonist-Tolazoline, Propranolol.

·        Cholinergic Drugs-Neostigmine, Pyridostigmine, Pralidoxime, Pilocarpine, Physostigmine.

·        Cholinergic Antagonists-Atropine, Hyoscine, Homatropine, Propantheline, Benztropine, Tropicamide, Biperiden *.

·        Diuretic Drugs-Furosemide, Chlorothiazide, Hydrochlorothiazide Benzthiazide, Urea, Mannitol, Ethacrynic Acid.

·        Cardiovascular Drugs-Ethyl nitrite, Glyceryl trinitrate, Alpha methyldopa, Guanethidine, Clofibrate, Quinidine.

·        Hypoglycemic Agents-Insulin, chlorpropamide, Tolbutamide Glibenclamide, Phenformin, Metformin.

·        Coagulants and Anti Coagulants-Heparin, Thrombin, Menadione, Bishydroxycoumarin, Warfarin Sodium.

·        Local Anesthetics-Lignocaine, Procaine, Benzocaine.

·        Histamine and Anti histaminic Agents-Histamine, Diphen Hydramine. Promethazine, Cyproheptadine, Mepyramine, Pheniramine, Chlorpheniramine.

·        Non-steroidal anti-inflammatory Agents-Indomethacin, Phenylbutazone, Oxyphenbutazone, Ibuprofen.

·        Antithyroids-Thyroxine, Methimazole, Methyl thiouracil, Propylthiouracil.

·        Diagnostic Agents-Iopanoic Acid, Propyliodone, Sulfobromophthalein Sodium, Indigotindisulfonate Sodium (Indigo Carmine), Evans blue, Congo Red, Fluorescein Sodium.

·        Steroidal Drugs-Betamethasone, Cortisone, Hydrocortisone, prednisolone, Progesterone, Testosterone, Oestradiol Nandrolone.

·        Anti-Neoplastic Drugs-Actinomycins, Azathioprine, Busulfan, Chlorambucil, Cisplatin cyclophosphamide, Daunorubicin, Hydrochloride, Fluorouracil, Mercaptopurine, Methotrexate.