Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2018 Publisher: Mercury Pharmaceuticals Ltd., Capital House, 85 King William Street, London EC4N 7BL, UK
Pharmacotherapeutic Group: Carbonic anhydrase inhibitors
ATC Code: S01EC01
Acetazolamide is a potent inhibitor of the enzyme carbonic anhydrase; the enzyme that catalyses the reversible reaction involving the hydration of carbon dioxide and the dehydration of carbonic acid. In the eye, this inhibitory action of acetazolamide decreases the secretion of the aqueous humor and results in a drop of intraocular pressure and is thus used to treat glaucoma.
DIAMOX SR is a sustained release formulation designed to obtain a smooth and continuous clinical response. Acetazolamide is readily absorbed after oral administration and binds tightly to plasma proteins as well as to the enzyme carbonic anhydrase. The drug begins to accumulate in tissues in which this enzyme is present notably red blood cells and the renal cortex. It is also bound to plasma proteins.
Peak plasma levels of the drug are reached 1-3 hours after oral administration with whole blood levels reaching peak concentrations approximately one hour later. Plasma levels decay more rapidly than red blood cell or whole blood levels with the elimination frequently being biphasic. The first phase having a half-life in 2 hours and the second phase in 13 hours. This terminal phase half-life corresponds to the leakage from red blood cells.
Acetazolamide is completely cleared by the renal route with the measured unbound renal clearance being some 5-6 times greater than creatinine clearance. Overall, clearance is dependent also on plasma protein binding.
Adverse reactions not observed in clinical studies, but seen in animals at exposure levels to clinical exposure levels and with possible relevance to clinical use were as follows:
Acetazolamide has been reported to be teratogenic (defects of the limbs) and embryotoxic in rats, mice, hamsters and rabbits at oral or parenteral doses in excess of ten times those recommended in human beings. Although there is no evidence of these effects in human beings, there are no adequate and well-controlled studies in pregnant women. (See section 4.6).
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