Dose-response study of nebulized bitolterol mesylate solution in asthmatic patients

Bitolterol mesylate, a new beta 2 adrenergic bronchodilator, is a "pro-drug" which is activated by esterases in the lung. In order to determine the optimal bronchodilator dose of bitolterol, six doses, (0.5 mg, 1.0 mg, 1.5 mg, 2.0 mg, 2.5 mg and 3.0 mg), were administered by closed-port, intermittent-flow nebulization (CPIF) to asthmatic patients on different days. For most patients, the onset of bronchodilator activity (FEV1 increase of at least 15 percent above baseline) occurred within 5 minutes and lasted at least 8 hours. Maximum mean increases in FEV1 were 46-50 percent at the 1.0 mg to 3.0 mg doses. Beyond the 1.0 mg dose, there was no significant improvement in bronchodilator effect, but adverse effects, particularly tremor, increased at higher doses. The optimal dose of bitolterol administered by CPIF was determined to be 1.0 mg which is similar to the dose of bitolterol recommended for use by metered-dose inhaler (MDI) which is 0.7 mg to 1.1 mg. If continuous-flow nebulization is used, two-three times more drug may be needed for a comparable effect. Bitolterol appears to be a safe, effective and long-lasting bronchodilator when administered by jet nebulization.