An isolated report describes a patient taking
quinidine who developed marked bradycardia when using timolol eye drops. Other reports describe orthostatic hypotension with
quinidine and
atenolol or propranolol.
Quinidine can raise
plasma metoprolol, propranolol, and timolol levels, but the
clinical relevance of this is uncertain. Additive QT-prolonging effects likely with
sotalol, see drugs that prolong the QT interval.
The general relevance of these case reports is unclear.