The effects of oral and subcutaneous administration of terbutaline in asthmatic patients.
In 8 asthmatic subjects, serum concentrations of terbutaline were correlated with changes in volume of air expelled in the first second of forced expiration (FEV1), other parameters of lung function, c-AMP plasma concentrations and finger tremor values after administration of either 5 mg terbutaline sulphate orally, 0.5 mg terbutaline sulphate subcutaneously or an oral placebo. Prior to the investigation, the patients had not used bronchodilators for 10-14 days. All lung function parameters and tremor values showed a significant correlation with the terbutaline (serum) concentrations in the central compartment and with the c-AMP plasma concentrations. FEV1 was the least variable lung function test. The maximal effect on FEV1 occurred 30-60 min after the subcutaneous dose and 2-4 h after the oral dose, corresponding with the maximal terbutaline serum concentrations and c-AMP plasma levels. In this study, the FEV1 improvement showed a linear relationship with the terbutaline serum concentrations between 1.6 and 6 ng/mL. Three out of 8 asthmatics showed an increase in tremor of more than 6 dB after subcutaneous administration, which corresponded with the awareness of this side-effect. In contrast to theophylline and anticholinergic agents, terbutaline serum concentrations showed a very low interindividual variance. As a consequence, the serum terbutaline concentration was almost predictable. However, the lung function improvement was not predictable since there seems to exist an individual sensitivity for this agonist.
D000284:Administration, Oral; D000328:Adult; D001249:Asthma / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D000242:Cyclic AMP / Q000097:blood; D005541:Forced Expiratory Volume; D006801:Humans; D007279:Injections, Subcutaneous; D008297:Male; D008875:Middle Aged; D013726:Terbutaline / Q000008:administration & dosage* / Q000009:adverse effects / Q000097:blood / Q000627:therapeutic use; D014202:Tremor / Q000139:chemically induced
D000242:Cyclic AMP; D013726:Terbutaline