Systemic and Local Tolerability of Ophthalmic Drug Formulations

Summary

All eye drops raise problems of local tolerance, but with variable frequencies. They can induce pain on instillation, allergic reactions, delayed healing, punctate keratitis, disturbances of lacrimal secretion, disturbances of accommodation (especially the parasympathomimetics) and local pigmentation after prolonged use. Corticosteroids are associated with 2 major risks: chronic glaucoma and cataract, initially reversible if treatment is stopped. There is still a major risk of corneal herpes with corticosteroids. It is important to be aware of these local problems as they are responsible for poor patient compliance.

The systemic effects essentially concern the agonists and antagonists of the autonomic nervous system. β-Blocker eye drops can cause bronchospasm, heart failure, syncope and psychiatric disorders, especially at high doses and with nonselective β-blockers. These consequences are usually related to failure to comply with the prescribing precautions. α-Adrenergic agonists, which exert dose-dependent effects, can induce hypertensive crises or angina attacks. Apart from patients at risk (children under the age of 30 months and the elderly), parasympathomimetics cause few systemic adverse effects; anticholinesterases, which have curare-like properties, are contraindicated for 6 weeks before general anaesthesia. In the very young and the very old, atropinic eye drops carry a risk of cardiovascular collapse and neuropsychiatric disturbances. Problems may also occur with other classes of drugs such as anti-infectives, antiseptics, anti-inflammatories and contact lens products. Nevertheless, it is clear that this form of treatment is generally very well tolerated in relation to the volume of eye drops prescribed by ophthalmologists each day.