Overuse can lead to systemic toxic effects. Timolol is a beta blocker and as such topical administration consistently reduces heart rate and shares with systemic beta blockers the ability to worsen congestive heart failure. Caution must be exercised in use with patients with a history of syncope, bradyarrythmias, heart block, fibrillation or infarction. Bronchospasm and exacerbation of asthma has been well documented after the use of timolol. Pulmonary function tests have been shown to worsen after only one drop .
Patients often experience paresthesias of their hands and face.
It can also cause hypokalemia and fatigue. GI intolerance can be a problem. In the elderly this rate should be slowed. They are useful in providing pain relief to patients with corneal abrasions and iritis. Recovery in 12 hours.