Acetazolamide-induced renal stone

Dorzolamide: development and clinical application of a topical carbonic anhydrase inhibitor

Systemic carbonic anhydrase inhibitors are among the most powerful agents to lower intraocular pressure. Unfortunately, their use is frequently accompanied by undesired side effects. Some are due to the relatively large amounts of drug that have to be systemically administered to inhibit the carbonic anhydrase in the ciliary processes. Recently, dorzolamide, a topical carbonic anhydrase inhibitor, has become commercially available for clinical use. This article reviews the development of topical carbonic anhydrase inhibitors with special reference to dorzolamide. When administered three-times daily, dorzolamide lowers intraocular pressure in a clinically useful manner. Ocular side-effects include frequent stinging and burning and allergy can develop. Systemic side effects have not been observed that could definitively be related to inhibition of extraocular carbonic anhydrase. Blood dyscrasias have not yet been observed. Absence of cardiovascular and pulmonary side effects, as can occur with beta adrenergic antagonists, and lack of pupillary and accommodative stimulation, as occur with cholinergic agonists, might make dorzolamide first-line medical treatment for elevated intraocular pressure.

Calcium metabolism in acidotic patients induced by carbonic anhydrase inhibitors: responses to citrate

Calcium metabolism and its response to citrate were examined in 51 patients with glaucoma receiving carbonic anhydrase inhibitors (acetazolamide or methazolamide). Metabolic acidosis, hypocitraturia and increased incidence of nephrolithiasis were induced by both drugs. However, the acidosis was milder with methazolamide administration. Normocalciuria was observed in 29 patients and was shown to be a result of low filtered calcium. Renal hypercalciuria in 16 patients was associated with elevated parathyroid hormone but nephrogenic cyclic adenosine monophosphate remained within normal limits. Citrate in the form of potassium citrate (4.3 mmol.) and sodium citrate (4.0 mmol.) did not correct the metabolic acidosis or hypocitraturia but consistently decreased fasting and 24-hour urinary calcium excretion in patients with renal hypercalciuria. This event did not occur in patients with normocalciuria or absorptive hypercalciuria. These results suggest that a small amount of citrate could reverse renal hypercalciuria without correcting the metabolic acidosis.

Urine composition and stone formation during treatment with acetazolamide

Twelve patients who formed renal stones during acetazolamide treatment for glaucoma were studied. Calcium phosphate was the dominating component in the stones. Long term treatment with acetazolamide decreased urinary citrate markedly, which will result in an increased ion-activity product of calcium phosphate and a decreased inhibiting property of urine on calcium phosphate crystallization. The treatment also increased urinary oxalate which together with a low citrate might increase the risk of calcium oxalate crystallization. However, an estimate of the ion-activity product of calcium oxalate in urine (AP [CaOx]-index) was unaffected by the treatment and calcium oxalate was a minor component of the stones.

Acetazolamide-induced renal calculi

The occurrence of urinary calculi associated with acetazolamide therapy is described. Patients with a history of urinary stones or surgery are a significant risk for further calculus formation when treated with acetazolamide. The concurrent use of sodium bicarbonate further potentiates this risk.