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Original, generic PGAs show no significant difference in IOP, tolerability
No significant difference was seen in efficacy and safety of prostaglandin analogues when comparing original and generics, according to a systematic review published in Ophthalmology Glaucoma.
“Three databases, PubMed, EMBASE and MEDLINE, were searched for randomized controlled trials from the marketing of the first PGA, latanoprost, in 1995 to the present date,” Alvilda T. Steensberg, MD, of the Department of Drug Design and Pharmacology at the University of Copenhagen in Copenhagen, Denmark, and colleagues wrote.
Researchers focused on 385 studies investigating the IOP-lowering effect of original prostaglandin analogues (PGAs) compared to their generic counterparts when treating individuals diagnosed with open-angle glaucoma (OAG) or ocular hypertension (OHT). The PGAs evaluated in these studies were latanoprost, travoprost, bimatoprost and tafluprost.
The primary outcome was reduction of IOP from the baseline. The secondary outcomes measured were tolerability, ocular surface health, quality of life, disease progression and cost-effectiveness.
Results included six studies involving 619 patients. Meta-analysis of all studies neglected to show clinically significant differences in efficacy between generic and original PGAs (0.23 mm Hg, CI -0.50 to 0.04 mm Hg). Both generic and original PGAs were well tolerated.
Because most studies evaluated showed at least one domain of low or unclear risk of bias, the quality of evidence is moderate, the researchers stated.
“This evidence is of moderate quality, but a small number of studies were available, and more randomized trials comparing other generic PGAs with original formulations would be useful to further investigate the robustness and generalizability of these findings,” the authors wrote. – by Erin T. Welsh
Disclosure: The authors report no relevant financial disclosures.
Perspective
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Practicing optometrists have the responsibility to determine the best initial topical drop treatment regimen for their OAG and OHT patients. This meta-analysis included six randomized controlled trials comparing the tolerability and efficacy of generic PGAs to their original counterpart. The review did not demonstrate clinically significant differences for either measure. These findings parallel prior evidence that generic PGAs provide IOP-lowering capabilities equivalent to that of brand PGAs.
Independent of IOP, the authors do mention other studies highlighting significant variations in the generic PGAs’ physical plastic bottle properties, drop size and, thus, the actual amount of administered medication, all of which may have clinical relevance (Kolko et al., Angmo et al.)
The relevance of these results are limited by the included trials’ suboptimal sample sizes, varying follow-up schedules and potential for variation in eyedrop ingredients between different PGA brands.
These results are not, at present, universally applicable in optometric practice. Further research of an extended duration (longer than 16 weeks) would be beneficial to comparatively assess generic and brand medications for differences in prevention of disease progression, beyond simply assessing their comparative efficacy. Removal of test bias and better implementation of standardized qualitative analysis is needed to assess the generic vs. brand PGA risk:benefit scale of adverse effects. Until then, the individual practitioner must consider what they feel best suits their patient, accounting for the severity of disease and the potential burdens imposed by the chosen medication.
References:
Angmo D, et al. Int Ophthalmol. 2017;doi:10.1007/s10792-016-0280-x.
Kolko M, et al. Acta Ophthalmol. 2017;doi:10.1111/aos.13355.
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