Drugs in ophthalmology

Drugs in ophthalmology

Most drugs used in ophthalmology are applied locally and are available as specific ophthalmic preparations such as eyedrops, gels, or creams. Local administration has two advantages: 1) minimal risk of systemic adverse effects (but no complete avoidance!) and 2) high local concentration. Some locally applied drugs can cause systemic adverse effects. The drugs can enter the systemic circulation via the nasal epithelium. In order to avoid this to happen, the lower lacrimal channel can be kept closed by hand for a minute after application of the eye drop. Another property that is desirable in ophthalmic drugs is the ability to pass across the cornea. Lipophilic or uncharged molecules have the best ocular penetration. Drugs prepared in highly viscous solutions such as gels or creams are in longer contact with the cornea, which might enhance their uptake trough the cornea. Iris pigmentation may affect the onset

and duration of action of many eye drugs. The more pigment is present (as in black and brown eyes), the more drug can bind to it, resulting in a slower and longer duration of action. The solution in which drugs for the eye are prepared is also important. Preservatives in eye drops can cause allergic reactions in susceptible patients. The pH of the solution influences the charge of the molecules (drug) in solution. Drugs solutions do not need to be isotonic with lacrimal secretion. Eye drop preparations need to be sterile and patients must take care not to contaminate or cross-contaminate from one eye to the other. Find more information on drugs in the eye in: ophthalmology.