The effect of timolol drops on respiratory function

Recently, attention has been focused on the adverse drug reactions of topical timolol, especially with regard to respiratory function in the elderly. This study was designed to assess whether timolol causes an alteration in lung function in patients without pre-existing respiratory disease and who have not suffered the impact of long-term beta 2 blockade.

A placebo-controlled randomised, double-masked, cross-over study was carried out on 20 ocular hypertensive patients with intraocular pressures over 21 mmHg, normal optic discs and full visual fields by Humphrey perimetry. Subjects received single-dose units of timolol maleate 0.5% drops or normal saline drops. Both were instilled in one eye or systemically (sublingually). The peak expiratory flow rate (PFR), forced expiratory volume (FEV), vital capacity (VC) and FEV/VC (%) ratio were all measured both before and after each type of drop and route of administration.

Two hours after instillation of timolol there was no change in PFR (p = 0.67) or VC (p = 0.40), but there was a fall in FEV (p = 0.038) and the FEV/VC (%) ratio (p = 0.041). The fall was greatest after topical administration.

Our results show that in our group of patients there was a tendency towards mild bronchial obstruction after topical timolol, although this was not clinically significant.