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Generic glaucoma medications gaining success in France, but concerns remain
Variations in stability, excipients and bottle design might lead to decreased efficacy, tolerability.
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PARIS — Generic glaucoma medications should be a treatment option, but specialists need to discuss this choice with their patients, monitor efficacy and tolerance and go back to the brand-name drops if necessary, according to a physician.
In France in 1999, pharmacists were allowed to dispense the generic equivalent in place of the brand-name drug. Generic substitution was not permitted if the patient refused it, if “may not substitute” was written on the prescription or if the substitute was not included in the official list of generics.
In July 2012, the regulation known as “tiers payant” was introduced. Patients now pay upfront for a branded drug if a generic equivalent is not available and are later reimbursed upon application.
“This has generated an unprecedented increase in generic penetration in France, allowing the French Social Security system to save 1.3 billion in 2012,” Jean-Philippe Nordmann, MD, said at the annual meeting of the French Society of Ophthalmology.
Questioning equivalence
Generic equivalents are or will soon be available for all glaucoma medications, including combinations. Once on the market, these drugs typically become popular quickly.
Nordmann said the generic latanoprost was introduced in France at the beginning of 2012 and by the end of the year, it accounted for 65% of the total sales. Timolol was introduced in July 2012 and 6 months later it accounted for one-third of the total sales.
“Interestingly, also brimonidine, which has been available for a long time, had a steep increase in the same year, from 45% in January to 65% in December,” he said.
By definition, generics are required to contain the same quantity and quality of active principle and to be available in the same dosage form. Bioequivalence should be proven by studies, but how and where it should be measured with topical ophthalmic medications is still an open question.
“There is no reliable way of measuring bioequivalence with eye drops and nobody does it. We can only assess that in the manufacturing process the quantity of active principle is within 10% of the amount contained in brand,” Nordmann said.
There are not many studies on efficacy, and they have had contrasting results, according to Nordmann.
Comparisons
In a randomized study of 266 patients, the comparison of Bausch + Lomb’s generic latanoprost with Xalatan (Pfizer) showed equivalent IOP reduction. But another randomized study carried out in India found remarkable differences, with a mean IOP reduction of 9.35 mm Hg using the brand vs. 5.76 mm Hg using the generic.
Additionally, the stability of the generic latanoprost was found to be affected by temperature. A significant reduction in the quantity of active principle at 25° or more was found, while Xalatan remained stable.
Excipients should be further discussed and are another parameter in assessing equivalence, Nordmann said.
He mentioned a case report of an 88-year-old patient, who on two occasions switched from Xalatan to the generic latanoprost (Kaken Pharmaceutical) and in both cases developed corneal ulceration.
“This was due to the presence of stearic acid polyesters added as a surfactant to the generic compound,” Nordmann said.
Additional problems may be related to composition and design of the bottles from which generic drops are dispensed. In a study, American and Canadian Timoptic-XE eye drops (Merck & Co.) were shown to vary significantly from the generics in drop volume, viscosity, and surface tension.”
Variations may hinder the quantity and easiness of administration, leading to under/over dosage or poor compliance,” Nordmann said. – by Michela Cimberle
- References:
- Allaire C, et al. Eur J Ophthalmol. 2012;doi:10.5301/ejo.5000041.
- Kahook MY,et al. Curr Eye Res. 2012;doi:10.3109/02713683.2011.631722.
- Narayanaswamy A, at al. Indian J Ophthalmol. 2007;doi:10.4103/0301-4738.30707.
- Mammo ZN,et al. Can J Ophthalmol. 2012;doi:10.1016/j.jcjo.2011.12.004.
- Takada Y, et al. Case Rep Ophthalmol Med. 2012;doi:10.1155/2012/536746.
- For more information:
- Jean-Philippe Nordmann, MD, can be reached at Hospital des XV-XX, 28 Rue de Charenton, 75012 Paris, France; +33-14-002-1204; email: jpnordmann@quinze-vingts.fr.
Disclosure: Nordmann is a consultant for Alcon, Allergan and Bausch + Lomb.