Sir,

Over the last week I have come across two patients who were using the wrong medications. One had been prescribed Predsol but was using Predsol-N, the other had been on Cosopt for some time, but had recently received Trusopt from his pharmacist.

It is clear that there is considerable room for confusion by general practitioners when renewing long-term prescriptions and by pharmacists at the point of sale when similarly named drops are concerned. The wrong medication may have significant consequences for the course of a patient's ocular condition, especially if a steroid is unnecessarily added or if a component in a combination glaucoma preparation is dropped.

Confusion is likely between:

Betagan and Betoptic,

Betnesol and Betnesol-N,

Ilube and Lacrilube,

Neomycin, Neosporin, and Neocortef,

Polyfax and Polytrim,

Predsol, Predforte, and Predsol-N,

Maxidex and Maxitrol,

Teoptic and Timoptol,

Tobramycin and Tobradex,

Trusopt and Cosopt,

Xalatan, Xalacom and Zaditen.

Errors in dispensing can be reduced if ophthalmologists limit the range of drops in a hospital formulary, by using generic names when possible, by writing prescriptions clearly and by educating local general practitioners, pharmacists, and junior doctors as to the similarities and differences between similarly named preparations.

When patients are seen in clinic, it is important to determine exactly what drops they are using and how often, even when you think you know what they are using. This not only gives opportunity to check a patient's level of compliance but may also reveal dispensing errors, such as those mentioned above, which may have bearing on a patient's apparent response to medication.

I can still vividly remember a patient nearly 20 years ago who was prescribed Timolol, 1 drop twice a day. His pharmacist prescribed Timolol, 2 drops three times a day which precipitated a severe asthma attack.

Checking which medications a patient is using is part of every patient consultation, even for patients reviewed with chronic conditions.