carbonic anhydrase inhibitors

carbonic anhydrase inhibitors

A class of drug that act by blocking the action of the enzyme CARBONIC ANHYDRASE. This enzyme greatly speeds up the reaction between carbon dioxide and water to form carbonic acid, a compound needed for the production of many of the body's secretions. Carbonic anhydrase is present in high concentration in the eye, the kidneys, stomach lining and pancreas. Inhibitor drugs reduce the rate of secretion of aqueous humour in the eye and is useful in treating GLAUCOMA. These drugs are also valuable in treating mountain sickness, periodic paralysis and absence attacks (petit mal). The group includes ACETAZOLAMIDE and DORZOLAMIDE.

diuretics

powerful drugs, often termed ‘water tablets’, that control hypertension and peripheral oedema; action of some local anaesthetics is antagonized by concomitant use of some diuretics (see Table 1), e.g. aldosterone antagonists (e.g. spironolactone); carbonic anhydrase inhibitors, e.g. acetazolamide; loop diuretics, e.g. furosemide; osmotic diuretics, e.g. mannitol; potassium-sparing diuretics, e.g. amiloride, or in combination with other diuretics; thiazide diuretics, e.g. bendroflumethiazide

Table 1: Principal drug interactions of local anaesthetic agents and other medications

Local anaesthetic agent Proprietary name	Principal drug interactions	Effect of interaction
Lidocaine Xylocaine	Antiarrhythmic agents Antibacterial agents Antipsychotics Antivirals Beta-blockers Diuretics Dolasetron Ulcer-healing drugs	Increased myocardial depression Increased risk of ventricular arrhythmias if lidocaine is given with quinpristin/dalfopristin Increased risk of ventricular arrhythmias if lidocaine is given with any drug that prolongs the QT interval of the cardiac cycle Plasma concentration of lidocaine increased by amprenavir, atazanavir and lopinavir Increased myocardial depression Increased risk of lidocaine toxicity when given with propranolol The action of lidocaine is antagonized by the hypokalaemia caused by acetazolamide, loop diuretics or thiazide and related diuretics (i.e. a greater dose of lidocaine would be required to achieve anaesthesia) Increased risk of ventricular arrhythmia if lidocaine is given with dolasetron Plasma concentration of lidocaine increased when given with cimetidine; risk of lidocaine toxicity increased with cimetidine
Bupivacaine Marcain Levo-bupivacaine Chirocaine	Beta-blockers	Increased risk of bupivacaine toxicity when given with propranolol Increased risk of myocardial depression if given with other antiarrhythmic agents
Prilocaine Citanest	Antiarrhythmic agents Antibacterial agents	Increased risk of myocardial depression if given with antiarrhythmic agents Increased risk of methaemoglobinaemia if given with sulphonamide antibacterial agents
Ropivacaine Naropin	Antidepressants	Metabolism of ropivacaine is inhibited by fluvoxamine, thereby enhancing the risk of ropivacaine toxicity
Mepivacaine Scandonest	Drug not listed in the British National Formulary

carbonic anhydrase inhibitors 

Drugs which inhibit the carbonic anhydrase enzyme in the ciliary epithelium of the ciliary body. This enzyme is essential for the formation of aqueous humour; its reduction results in a decrease in intraocular pressure. Those in use are sulfonamide derivatives. They are administered systemically (e.g. acetazolamide) or topically in the treatment of glaucoma. Examples: acetazolamide, brinzolamide, dichlorphenamide, dorzolamide.