| Acetazolamide Pharmacology |
| Acetazolamide |
| About Acetazolamide |
| Carbonic Anhydrase Inhibitor, Anticonvulsant, Diuretic, Ophthalmic Agent- Antiglaucoma. |
| Mechanism of Action of Acetazolamide |
| It is a sulfonamide derivative of carbonic anhydrase enzyme inhibitor. It exerts it`s diuretic, anti glaucomal, anti convulsant, anti altitude sickness actions by non competitively and reversibly inhibiting carbonic anhydrase in renal proximal tubules, ciliary body of eye, brain, lungs and tissues etc. Diuretic action: The inhibition of carbonic anhydrase at proximal renal tubules resulting in slowing of hydration of carbon dioxide which leads to decreased availability of H+ to exchange with luminal sodium. Inhibition of brush border carbonic anhydrase retards dehydration of carbonic acid in the tubular fluid so that less carbon dioxide diffuses back in to the cells. Thus inhibits bicarbonate and Na+ reabsorption in proximal tubules. It also inhibits secretion of H+ in collecting duct and distal tubule. K+ is also lost in excess due to Na+ exchange in distal tubule takes place only with potassium. The drug promotes excretion of bicarbonate, sodium, potassium and water. Anti glaucomal action: By inhibiting carbonic anhydrase in ciliary body of eye it reduces aqueous formation by limiting generation of bicarbonate in the ciliary epithelium lowers intraocular tension. Anticonvulsant action: By inhibiting carbonic anhydrase in the brain it increases the carbon dioxide levels in brain which leads to increased acidity and raising seizure threshold. Vertigo: Diuretics are used in vertigo in assumption that vertigo is due to endolymphatic hydrops. They reduce labyrinthine fluid pressure. Anti altitude sickness agent: It shortens the period of high altitude acclimatization by preventing conversion of carbon dioxide in to bicarbonate it increase carbon dioxide tension in tissues and decreases it in lungs |
| Pharmacokinets of Acetazolamide |
| Absorption: Well absorbed orally, Distribution: Widely distributed in to the body tissues. Metabolism: Not metabolized in the body. Excretion: Excreted unchanged in urine. |
| Onset of Action for Acetazolamide |
| 60 to 90 minutes |
| Duration of Action for Acetazolamide |
| 8 to 12 hours |
| Half Life of Acetazolamide |
| N/A |
| Side Effects of Acetazolamide |
| 1.Numbness and tingling in fingers 2.Taste disturbances 3.Hypokalemia 4.Acidosis 5.Blurred vision 6.Headache 7.Drowsiness 8.Paresthesia 9. Fatigue 10.Abdominal discomfort 11.Nausea 12.Fever 13.Rashes 14.Allergic reactions 15.Bone marrow depression(rare) 16.Ototoxicity |
| Contra-indications of Acetazolamide |
| 1.Hypersensitivity to the drug 2.Hyponatremia 3.Hypokalemia 4.Renal impairment 5.Hepatic impairment 6.Adrenal insufficiency 7.Long term management of non congestive chronic angle closure glaucoma 8.Hyperchloremic acidosis. |
| Special Precautions while taking Acetazolamide |
| 1.Diabetes mellitus 2.Sickle cell anaemia 3.Gout 4.Hypesensitivity to Sulfonamides 5.Chronic obstructive pulmonary disorders 6.Emphysem 7.Respiratory acidosis 8.Along with other diuretics |
| Pregnancy Related Information |
| Contraindicated. |
| Old Age Related Information |
| Use with caution |
| Breast Feeding Related Information |
| Contraindicated. |
| Children Related Information |
| N/A |
| Indications for Acetazolamide |
| 1.Epilepsy 2.Edema in heart failure 3.Open angle glaucoma 4.Acute angle closure glaucoma 5.Acute mountain sickness 6.Benign intracranial hypertension. 7.Vertigo |
| Interactions for Acetazolamide |
| Amphetamine, Ephedrine, Flecainide, Pseudoephedrine, Quinidine: Potentiates effect by decreasing their renal excretion. Digitalis: Digitals toxicity since it induces hypokalemia Primidone: May delay absorption. Salicylates: Salicylate toxicity due to metabolic acidosis. Corticosteroids: Hypokalemia. Lithium: Efficacy diminished. Sulfonamides: Aids penetration across Blood/CSF barrier. Folic acid antagonists, Oral hypoglycaemic agents, Mercurial diuretics and Oral anticoagulants: May potentiate effect. Lab Test: Urinary Proteins Determination – False positive results. |
| Typical Dosage for Acetazolamide |
| Glaucoma: 250mg 1 to 4 times daily Epilepsy: Adults & Children: 8 to 30mg/kg/day in 2 to four divided doses. Edema in heart failure: 250 to 375mg daily in the morning Children: 5mg/kg/day orally or I.V. in the morning. Acute mountain sickness: 250 mg 2 to 3 times daily or 500mg extended release formulation twice daily take 48 hours before ascent and continue until 48 hours after arrival at high altitude. |
| Schedule of Acetazolamide |
| H |
| Storage Requirements for Acetazolamide |
| Store in a well closed container at a temperature range of 15 to 30 degree C. |
| Effects of Missed Dosage of Acetazolamide |
| Take the missed dose as soon as noticed and if it is the time for next dose then skip the missed dose. Continue the regular schedule. Do not double the dose. |
| Effects of Overdose of Acetazolamide |
| Treatment is supportive and symptomatic. Drug is removed by induced emesis or gastric lavage. Monitor & support serum electrolyte level and blood acidosis. Acidotic state can be corrected by administration of bicarbonate. Perform dialysis if required in conditions such as renal failure. |
