Long-term drift and timolol therapy: possible role for pulsed therapy.

Eyes treated with a topical betablocker may exhibit the phenomenon of longterm drift, leading to loss of intraocular pressure control. It has been suggested that discontinuation of the betablocker may restore sensitivity to betablocker therapy, and that this phenomenon might be enhanced by the administration of an adrenergic agonist during this holiday period. This study was set up to examine further this hypothesis. Nine patients with ocular hypertension receiving treatment with timolol were entered into the study. Timolol was discontinued then re-started after four weeks of treatment with dipivefrin. This treatment cycle was repeated after a further four weeks. IOP was measured every two weeks. Re-introduction of timolol was associated with a significant lowering of IOP at two weeks (3.2 mmHg in the first cycle, p < 0.01, 3.4 mmHg in the second cycle, p < 0.01). Discontinuation of timolol and treatment with dipivefrin was not associated with a significant change in IOP.