Pemirolast potassium (TWT-8152) is a histamine H1 antagonist and mast cell stabilizer that acts as an antiallergic agent. Target: Histamine H1 Receptor Pemirolast potassium (TWT-8152) is a new oral, nonbronchodilator antiallergy medication that is being evaluated for the therapy of asthma [1]. Pemirolast potassium (TWT-8152) inhibits chemical mediator release from tissue mast cells and is also shown to inhibit the release of peptides including substance P, Pemirolast potassium (TWT-8152) reduces kaolin intake by inhibition of substance P release in rats [2]. Pemirolast potassium (TWT-8152) potently attenuates paclitaxel hypersensitivity reactions through inhibition of the release of sensory neuropeptides in rats [3]. Pemirolast potassium (TWT-8152) potassium is used for the treatment of allergic conjunctivitis and prophylaxis for pulmonary hypersensitivity reactions to drugs such as paclitaxel [4].