Terbutaline has greater selectivity for beta2 adrenoreceptors and is longer acting. It is the only Beta2 selection bronchodilator available for parenteral use for emergency treatment of status asthmatics. Terbutaline is incompletely absorbed from gastrointestinal tract and undergoes 40% first-pass metabolism by conjugation in liver.
MECHANISM OF ACTION
Terbutaline selectively stimulates Beta2 receptors present in the smooth muscles of bronchi and bronchioles. This activates the enzymes Adenyl cyclase leading to formation of intracellular cyclic AMP (Cyclic Adenosine Monophosphate) from ATP (Adenosine Triphosphate). Increased intra cellular concentration of cyclic AMP produces bronchodilation.
Being a highly selective Beta2 stimulant, Terbutaline by and large does not produce side effects. Palpitation, tachycardia, rise in blood pressure and headache which is common with ephedrine is practically absent with Terbutaline. Terbutaline can produce fine tremor of hands during the initial period of therapy, in some cases which usually disappear on continuation. Sometimes, it may require reduction in dosage and very rarely discontinuation of therapy.
IN PRODUCTIVE COUGH ASSOCIATED WITH
- Chronic Bronchitis
- Bronchial Asthma
1-2 teaspoonful 2-3 times daily