Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
Xalatan (Pharmacia & Upjohn)
2.5 mL in 5 mL bottles
Latanoprost is a synthetic analogue of prostaglandin F2. When instilled into the eyes, the drug is absorbed through the cornea and hydrolysed to its active form. The outflow of aqueous humour is increased and therefore intraocular pressure falls.
The peak concentration in the eye is reached two hours after a dose, but the maximum effect occurs after 8-12 hours. As intraocular pressure remains reduced for at least 24 hours, latanoprost only needs to be used once a day. Approximately half of a dose is absorbed systemically and then metabolised in the liver.
Latanoprost has been compared with timolol in randomised double-blind studies. After 6 months, intraocular pressure was reduced by 27-34% in the latanoprost group and by 20-33% in the timolol group.
Adverse events occur in 5-15% of patients. Common complaints are burning, stinging and itching, redness of the eyes and blurred vision. With time, the pigmentation of the iris may change. This alteration in eye colour affected approximately 7% of the 460 patients who took latanoprost during clinical trials.
At present, the long-term effects of latanoprost are unknown. Will treatment prevent loss of vision due to glaucoma? The drug has only been approved for the reduction of elevated intraocular pressure in patients with open-angle glaucoma and ocular hypertension who are intolerant of, or insufficiently responsive to, other drugs. Although this suggests that latanoprost may be added to other treatments, there are limited data on combined therapy.