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New formulation of brimonidine reduces drug exposure, enhances penetration
Allergan’s new 0.1% formulation of Alphagan P also helps reduce side effects associated with stronger formulations.
A new lower-concentration formulation of brimonidine decreases the systemic absorption of the drug, creating less dry mouth, fatigue and other side effects, but leaves its IOP-lowering effect intact, according to Steven T. Simmons, MD.
Dr. Simmons said he has used the 0.1% formulation of Alphagan P (brimonidine tartrate ophthalmic solution, Allergan) in clinical trials for the past year in 100 patients. In a telephone interview with Ocular Surgery News, Dr. Simmons said that, for open-angle glaucoma and ocular hypertension patients, the reduced concentration “works as effectively as, if not better than” the earlier 0.15% and 0.2% formulations of the drug.
Alphagan P 0.1% received FDA premarket approval in August, based on 12-month results of a clinical trial. Allergan designed the formulation to provide the smallest dose of brimonidine that effectively lowers IOP, according to information from the company.
“Everyone will agree that 0.15% was a great step forward for the Alphagan P product,” Dr. Simmons said. “We think that 0.1% is another significant step, which is going to help reduce the systemic side effects and maintain, if not slightly improve, the efficacy.”
Past solutions
According to Dr. Simmons, the initial 0.2% formulation of Alphagan was an acidic solution. When it was reformulated as Alphagan P 1.5%, the pH level was adjusted to a more physiologic 7.2. He said researchers learned that with the reformulation, the penetration of the drug through the cornea was greater. They have now “carried further” that finding with the 0.1% formulation, which has a pH level of 7.6, Dr. Simmons said. By moving the pH level in the drug to slightly basic, the ocular penetration is even more greatly enhanced, he said.
“You can reduce the drug exposure because of this improved ocular penetration,” he said.
From the original 0.2% formulation to Alphagan P 0.1%, the concentration of drug has been decreased by 50% without sacrificing efficacy, company literature noted.
Dr. Simmons said the 0.1% formulation provides as much concentration of drug in the anterior chamber as the 0.15% formulation did. As a result, the pressure-lowering efficacy of the 0.1% formulation is as strong as that of the 0.15% and 0.2% formulations, he said.
A clinical trial found that the difference in mean IOP reduction between Alphagan P 0.1% and the original solution Alphagan 0.2% ophthalmic solutions was less than 1 mm Hg at all follow-up times over a 12-month period, according to Allergan.
Dr. Simmons said he has begun switching his patients who had been on Alphagan P 0.15% to the new 0.1% formulation, especially those who have experienced any systemic side effects such as fatigue or dry mouth. He has also been using the new formulation with new patients.
Dr. Simmons said he uses Alphagan P mainly as an adjunctive therapy.
“It’s very effective when added to a lipid, a prostaglandin,” he said. “That’s really where its biggest niche is, being added either to latanoprost, bimatoprost or travoprost.”
For Your Information:
- Steven T. Simmons, MD, can be reached at 1240 New Scotland Road, Slingerlands, NY 12159; 518-475-7300; glaucomaconsult@aol.com.
- Allergan Inc., maker of Alphagan P 0.1%, can be reached at P.O. Box 19534, Irvine, CA 92623; 714-246-4500; 714-246-4971; Web site: www.allergan.com.
- Erin L. Boyle is an OSN Staff Writer who covers all aspects of ophthalmology.