Intraocular pressure‐lowering efficacy of bimatoprost 0.03% and travoprost 0.004% in patients with glaucoma or ocular hypertension

Short abstract

The efficacy of bimatoprost and travoprost in patients with glaucoma and ocular hypertension

Dr Cantor's article¹ (see page 1370)on the efficacy of bimatoprost and travoprost in patients with glaucoma and ocular hypertension shows again that both these drugs are efficacious in lowering intraocular pressure (IOP). The study is a prospective, randomised investigator‐blinded trial, which has results similar to those found in studies carried out with the drugs in this class.

Dr Cantor found that bimatoprost lowered IOP slightly more than travoprost in this study population. This is the first relatively large two‐arm study to show this in a head‐to‐head design. The current study supports others who have shown that bimatoprost is somewhat more efficacious than travoprost.

What is reassuring about this study is that there are no surprises, and the results appear to be consistent with what has been seen in the collection of other studies comparing drugs in this class. The relative degrees of IOP reduction, rates of hyperaemia and clinical success parameters are within the range reported in smaller studies and larger multiple comparison studies.²,³,⁴,⁵,⁶

What has differed from study to study is the cohort of patients examined, and the treatment of the data both from the standpoints of study design and statistical treatment. These factors can influence the results to some extent, but taken in the context of the body of information we have at hand, the results fall into a range with certain trends evident. For example, in the Cantor study, bimatoprost was found to be more efficacious in lowering IOP than travoprost and the degree of difference is somewhat different from that reported in other studies, but similar. Also, the hyperaemia rate was higher with bimatoprost than travoprost. In this study, the difference was not significant, although it has been in others.²

The clinical question at hand is, “are the differences found in studies like the current one clinically relevant?” The first issue is which agent should be chosen to primarily treat a new patient with glaucoma or ocular hypertension. The second clinical issue is, “are the differences in efficacy enough to switch between agents in this group if the first one is not as efficacious as necessary for an individual patient?” Neither of these issues exist in a vacuum and in the real world; there are issues such as formulary status, hyperaemia and bottle differences. It is reassuring that both the drugs work well in lowering IOP. It gives practitioners confidence if choices are restricted by formulary issues.

Although studies such as Dr Cantor's may show differences between populations, individual differences are more difficult to tease out of the data. When treating glaucoma and ocular hypertension, there is an increasing body of evidence showing that it may be important to decrease IOP consistently, so as to minimise the occurrence of higher IOPs at which the damage to the optic nerve may occur.

The authors in this study chose to emphasise mean IOP reduction. Mean IOP is a commonly used parameter that gives an overall impression of efficacy, but it can be influenced by outlier data points and it assumes that all patients follow a similar IOP curve throughout the day and over time. This may or may not be true. We are increasingly aware that an individual patient's IOP stability may be a more important factor in controlling the progression of glaucoma.

Both bimatoprost and travoprost have fairly flat diurnal curves when group means are evaluated. It would be interesting and helpful to analyse these data and other similar data looking at the profiles of individual patients. This would be useful in confirming our impression that these drugs are indeed superior to those in other classes when used as monotherapy. Likewise, if we do see a difference between the drugs, we might be more likely to use them preferentially over another that does not have this feature.

On the basis of this, there is probably no need to conduct a study similar to Dr Cantor's again. What is needed, however, is a look at data in terms of fluctuation. Looking for statistical significance in regard to the differences among the drugs in terms of lowering IOP at a given time point is probably no longer a worthwhile endeavour, given the body of evidence that is presently available in literature. Further information about this group of drugs compared with others and more information about combination treatment is the next step.

Bimatoprost and travoprost along with latanoprost have changed the way the glaucoma has been treated over the past 5 years. These drugs have become the de facto preferred treatments for glaucoma. Furthermore, with the recent Food and Drug Administration recommendation for bimatoprost to be used as a first‐line agent, the choice really becomes one of choosing the agent that offers the best chance of clinical success. The current study adds to the body of information about the relative efficacy of these drugs and will help clinicians make decisions via evidence‐based medicine.