A double-blind evaluation of skin test suppression produced by two doses of terfenadine

For some patients, terfenadine, in the currently recommended dose of 60 mg twice daily (bid), may be only modestly effective in the treatment of allergic rhinitis. In a double-blind placebo-controlled crossover study of 12 patients, a larger dose (300 mg bid) was evaluated for its suppression of titrated skin tests to histamine and compound 48/80 to determine whether this regimen might result in greater suppression while it maintained the freedom from side effects of the presently recommended dose. In seven patients, skin test suppression by these two doses of terfenadine, each administered for 3 days, was compared to that produced in an earlier study by 3 days of treatment with chlorpheniramine (8 mg three times a day). The 300 mg bid terfenadine regimen produced significantly greater skin test suppression (p < 0.05) than the currently recommended 60 mg bid dose. There was no significant difference in side effects between the two doses, and neither active treatment regimen produced more side effects than placebo treatment. Both doses of terfenadine suppressed cutaneous reactivity significantly more than had chlorpheniramine. It is concluded that the presently recommended dose of terfenadine produces submaximal skin test suppression and that further studies are needed to investigate the clinical efficacy and safety of larger doses of terfenadine in the treatment of allergic rhinitis.