Comparison of the effectiveness and safety of monotherapy with 0.03% bimatoprost (Bimatan®) and 0.005% latanoprost (Xalatan®) in patients with primary open-angle glaucoma

PURPOSE: Comparative evaluation of the hypotensive effect and tolerability of two drugs — bimatoprost 0.03% (Bimatan) and latanoprost 0.005% (Xalatan) — when used as the treatment of choice in patients with stage I-II primary open-angle glaucoma (POAG).
MATERIALS AND METHODS: The action of latanoprost 0.005% (Xalatan) was studied for 3 months on cases of 51 patients with POAG (59 eyes), among which 17 males with average age of 65.2 years, and 34 females with average age of 64.1 years. All patients suffered from newly diagnosed primary open-angle glaucoma: stage I — 29 patients (56.9% of 51 patients), stage II — 22 patients (43.1% of 51 patients). The degree of width of the anterior chamber angle according to the Schaffer classification was 3-4, the degree of pigmentation of the angle according to A.P. Nesterov — 1-2. Visual acuity of the study patients ranged from 0.4 to 0.8 without correction.
Treatment outcomes of the latanoprost study are compared with a previous study of bimatoprost 0.03% (Bimatan) used for 3 months in the treatment of 46 patients (64 eyes) with POAG. The bimatoprost study included 26 males with the average age of 61.3 years and 20 females with the average age of 65 years; among them, 31 (67.4% of 46 patients) with stage I glaucoma and 15 (32.6% of 46 patients) with stage II glaucoma. The degree of width of the anterior chamber angle according to the Schaffer classification was 3-4, the degree of pigmentation of the angle according to A.P. Nesterov — 1-2. Visual acuity of the patients varied from 0.2 to 0.8 without correction.
All patients underwent a comprehensive ophthalmological examination, which included visometry, ophthalmoscopy and gonioscopy, computerized perimetry, tonometry, and tonography. The drugs were applied daily, 1 drop into the affected eye at 8 p.m. daily. The follow-up tonography, as well as assessment of changes with visometry and computerized perimetry was carried out 3 months after the start of daily systemic therapy.
RESULTS: After 3 months of 0.03% bimatoprost instillations, IOP has decreased from 17.2±3.1 to 13.8±1.6 mm Hg, mainly due to an increase in the ease of aqueous humor outflow from 0.081±0.042 to 0.198±0.038 mm3/min/mm Hg, as well as a tendency towards decrease in the production of aqueous humor from 0.91±0.18 to 0.76±0.11 mm³/min (p<0.05). Becker’s coefficient has decreased from 161.9±36.1 to 63.1±9.3 due to the decrease in P₀ and reduced retention of aqueous humor.
After 3 months of 0.005% latanoprost instillations, IOP has decreased from 21.5±2.3 to 18.4±1.7 mm Hg due to an increase in the ease of aqueous humor outflow from 0.097±0.064 to 0.201±0.043 mm³/min/mm Hg. Becker's coefficient has decreased from 159.7±37.4 to 60.1±10.5. No significant decrease in the production of aqueous humor was noted (p>0.05).
The use of bimatoprost caused the following side effects: 2 patients (4.35% of 46 patients) felt burning sensation in the eye after instillations, 6 patients (13% of 46 patients) had mild conjunctival hyperemia. Thus, 8 patients (17.4% of 46 patients) experienced unwanted side effects. The systematic use of latanoprost 0.005% caused fewer side effects: 2 patients (3.9% of 51 patients) experienced a burning sensation in the eye after instillation.
None of the patients had to discontinue the use of the drugs due to these side effects.
CONCLUSION: Prostaglandin F2α analogs are known to have pronounced and long-term hypotensive effect due to facilitation of the outflow of intraocular fluid. The comparative study of the effectiveness of bimatoprost and latanoprost shows that despite them both belonging to the same group, there are certain differences in the degree of their hypotensive effect and in the mechanism of action: bimatoprost reduces intraocular pressure by facilitating the outflow and reducing the production of intraocular fluid, which provides it with certain advantages over latanoprost. Thus, the pronounced hypotensive effect of bimatoprost is realized through simultaneous action on two components of the pathogenesis of ophthalmic hypertension. For the moment, both bimatoprost and latanoprost are undoubtedly the first choice drugs for the treatment of patients with early and advanced glaucoma.

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