Mechanism of Action

Pemirolast potassium is a mast cell stabilizer that inhibits the in vivo Type I immediate hypersensitivity reaction.

In vitro and in vivo studies have demonstrated that pemirolast potassium inhibits the antigen-induced release of inflammatory mediators (e.g., histamine, leukotriene C₄, D₄, E₄) from human mast cells^.

In addition, pemirolast potassium inhibits the chemotaxis of eosinophils into ocular tissue and blocks the release of mediators from human eosinophils.

Although the precise mechanism of action is unknown, the drug has been reported to prevent calcium influx into mast cells upon antigen stimulation.

Pharmacokinetics

Topical ocular administration of one to two drops of ALAMAST ophthalmic solution in each eye four times daily in 16 healthy volunteers for two weeks resulted in detectable concentrations in the plasma. The mean (±SE) peak plasma level of 4.7 ± 0.8 ng/mL occurred at 0.42 ± 0.05 hours and the mean t_1/2 was 4.5 ± 0.2 hours. When a single 10 mg pemirolast potassium dose was taken orally, a peak plasma concentration of 0.723 µg/mL was reached.

Following topical administration, about 10—15% of the dose was excreted unchanged in the urine.

Clinical Studies

In clinical environmental studies, ALAMAST™ was significantly more effective than placebo after 28 days in preventing ocular itching associated with allergic conjunctivitis.

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