Pemirolast

Pemiralast 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 pernirolast inhibits the antigen-induced release of inflanunatory mediators (e.g., histamine, leukotriene C4, D4, E4) from human mast cells.

In addition, pemirolast inhibits the chemotaxis of eosinophils into ocular tissue and blocks the release of mediators from human easinophils. Although the precise mechanism of action is unknown, the drug has been reported to prevent calcium influx into mast cells upon antigen stimulation.

Topical ocular administration of one to two drops of pemirolast ophthalmic solution in each eye four times daily in 16 healthy volunteers for two weeks resulted in detectable concentrations in the plasma. The can (±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 mg/mL was reached.

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