Expert Interview: Prescribing Generics with Paul Schacknow, MD

Has the release of generic latanoprost changed your prescribing habits?

Dr. Schacknow: Six generic versions of latanoprost are currently available in the Unite States. The FDA requires these drugs to contain essentially the same active ingredient as the original branded latanoprost, but they may have different excipients and are packaged in various plastic containers of different shape and molecular composition from the original. Studies have found that prostaglandin analogues (PGAs) are absorbed by the plastic of the dispensing bottle, and they may be absorbed to different extents depending on the composition of the plastic. The concentration of active ingredient available toward the end of the amount of solution in the bottle may vary from generic brand to generic brand, and also may be less than that of the original branded product based on differential uptake of the PGA by the container walls.

No clinical testing in humans or animals is required of these generic products as compared with the clinical trials that led to FDA premarket approval of the original branded latanoprost.

Finally, patients receiving generic latanoprost may receive generics from different manufacturers at each refill if the pharmacy or managed care formulary committee sees some economic advantage to that.

Of course, patients reasonably want to receive the least-expensive product. But I think it is our duty to discuss the risks of generics and benefits of branded products (consistent product, consistent dispensing bottle, possible side effects of known inactive ingredients) with the patients and involve them in the prescribing decision.

For all these reasons, I usually prescribe branded travoprost or bimatoprost unless economic issues are paramount to the patient. While some patients have idiosyncratic IOP responses to the different branded PGAs, I have usually found the branded products to be similar in their ability to lower IOP. I generally like to minimize the disruptive ocular surface effects of the preservative BAK, so my first choice PGA tends to be travoprost with Sofzia as a preservative.

Do you have any experience with generic latanoprost? What is your assessment with regard to patient acceptance or side effects?

Dr. Schacknow: Some patients do have problems with dispensing drops from some of the generic bottles. “Streaming” has been noted. Anecdotal reports from my patients and other physicians suggest that some patients notice some ocular surface irritation with the generic products compared with the original branded latanoprost. A few patients have asked me to switch them back to branded latanoprost or another product based on ocular discomfort. I don’t have enough patient experience yet with generic latanoprost used as monotherapy to offer reliable comments on long-term IOP control with the generic products.

Assuming no contraindications, which is your preferred adjunctive medication to add to a prostaglandin analogue?

Dr. Schacknow: Considerable literature suggests the following:

a single (not combined) agent should be the first adjunctive step to a PGA
beta-blockers do not work at night
alpha-agonists do not work at night and have a high percentage of patients with ocular allergy
topical carbonic anhydrase inhibitors produce additional lowering of IOP when added to a PGA, and in most studies I have read, do so better than a beta-blocker
topical carbonic anhydrase inhibitors do work at night. Dorzolamide and brinzolamide both seem equally efficacious to lower IOP, and brinzolamide has the advantage of being branded (with consistency) and comes in a suspension with a less-acidic pH than dorzolamide—it is thus the more comfortable of the two and is usually preferred by patients.

How many medications do you consider maximal medical therapy prior to recommending surgery?

Dr. Schacknow: I no longer believe in maximal tolerated medical therapy. That philosophy often resulted in too many drugs for good adherence, too much preservative load, and too much cost for the patient. I do subscribe to the tenant of maximal reasonable medical therapy. In my practice, with of course the occasional exception, patients should use no more than two different bottles of glaucoma drops. Sometimes one bottle may be a combination product, so while most patients requiring adjunctive therapy would be receiving at most two medications, some might be using two bottles but receiving three medications. The rare patient might have additional medical therapy, but most patients requiring additional pressure lowering after “two bottles” would receive laser trabeculoplasty or, in some smaller percentage of cases, incisional glaucoma surgery.

Have you found or developed a system in your practice that helps you keep track of the tier assignment of glaucoma medications for the various health plans in which you participate?

Dr. Schacknow: Our multispecialty ophthalmology group participates in dozens of health insurance plans. We have taken the top five plans, in terms of patient encounters, and made a printed list of the tier structure for most of the glaucoma medications, both branded and generic. We check the accuracy of this list every several months. Of course, industry sales representatives rapidly bring changes in tier status for their medications to my attention!