Absolute bioavailability of terbutaline from a CR-granulate in asthmatic children.

The study aimed at finding the absolute bioavailability of terbutaline of a newly developed CR-granulate. Eight asthmatic children, aged 8-13 years, were given 3 mg of terbutaline as the CR-granulate, concomitant with the intravenous administration of 0.100 mg of deuterium-labelled terbutaline. The labelling of the intravenous dose made possible a separation, in the analytical step, of terbutaline originating from the intravenous and oral administration. Maximal plasma concentration, 8.7 (range: 4.9-15.2) nmol l-1, was reached after 4.7 (2.2-6.0) h. Absolute bioavailability was 10.8 (7.63-16.4) per cent. The parameter values were similar to those found after administration of terbutaline CR-tablets to adults. The CR-formulation is easily swallowed and can be dosed twice daily. Thus it should be a good alternative to elixir or plain tablets, dosed three times a day.