Effect of timolol eye drops in subjects receiving systemic propranolol therapy.

In a double-blind controlled study seven healthy subjects with normal eyes were given alternatively a placebo or 80 or 160 mg of propranolol per day, with an interval of at least 1 week between the three experiments. Two hours after a dose of the medication was taken, two drops of 0.5% timolol maleate were instilled into one eye, and for the next 4 hours the intraocular pressure, pulse rate and blood pressure were measured hourly. Timolol reduced the intraocular pressure substantially and to the same extent in the subjects who had taken a placebo and those who had taken 80 mg of propranolol per day; however, it had almost no effect in those who had taken 160 mg of propranolol per day. There was marked interindividual variation in the response to timolol. No change in the pulse rate or the blood pressure was noted. A similar study was carried out with 12 patients taking propranolol for various cardiovascular problems; their dosage of this agent was not varied, however. The results were basically the same, except that the patients taking 120 mg of propranolol per day had an intermediate response to timolol.