All Eyes on Hyperkalemia: A Case Report of Timolol Ophthalmic Drops Leading to Hyperkalemia

Nonselective β-blockers are a class of medication that competitively antagonize the β₁ and β₂ adrenergic receptors. Nonselective β-blockers include such agents as timolol, propranolol, and nadolol, among others. In particular, certain nonselective β-blockers may be used as intraocular pressure-lowering agents for the treatment and management of elevated intraocular pressure and glaucoma. Herein, we present a case of chronically elevated plasma potassium levels in a patient with glaucoma, attributable to the systemic hyperkalemic effects of the ophthalmically administered nonselective β-blocker timolol, an adverse effect which has only rarely been reported. Discontinuation of ophthalmic timolol-and a switch to a different intraocular pressure-lowering agent-resulted in the prompt normalization of plasma potassium levels and reversal of the hyperkalemia, without the need for any further subsequent interventions. The aim of this report is to highlight the potential for topical ophthalmic timolol to cause hyperkalemia, as well as propose potential mitigation and management strategies for patients with elevated potassium levels.