Drug Interactions between dorzolamide ophthalmic and Synalgos-DC

GENERALLY AVOID: The combination of large doses of salicylates and oral carbonic anhydrase inhibitors (CAI) may rarely result in severe metabolic acidosis and/or salicylate toxicity. The mechanism is unknown but may involve salicylate-induced displacement of CAIs from plasma protein-binding sites and reduced renal clearance, or CAI-induced plasma pH changes resulting in increased amounts of unionised salicylates entering the CNS. Coma and death have been reported. Although this has not been reported with ocular CAIs, the clinician should consider the possibility of an interaction with these agents, also.

MANAGEMENT: In general, concomitant use of antirheumatic doses of salicylates and oral CAIs is not recommended. If coadministration is necessary, careful monitoring of the patient's mental status and acid base balance is strongly recommended. Patients should be advised to promptly notify their physicians if they experience symptoms such as lethargy, tinnitus, confusion, nausea, vomiting, or hyperventilation.

One study has reported that coadministration of caffeine and aspirin lead to a 25% increase in the rate of appearance and 17% increase in maximum concentration of salicylate in the plasma. A significantly higher area under the plasma concentration time curve of salicylate was also reported when both drugs were administered together. The exact mechanism of this interaction has not been specified. Physicians and patients should be aware that coadministration of aspirin and caffeine may lead to higher salicylate levels faster.