Patients with known hypersensitivity to Terbutaline.
The frequency of side-effects is low at the recommended doses. Side-effects which have been recorded such as tremor, headache, tonic cramp and palpitations are all characteristic of sympathomimetic amines. A few patients feel tense; this is also due to the effects on skeletal muscle and not to direct CNS stimulation. Whenever these side-effects have occurred the majority have usually been spontaneously reversible within the first week of treatment. Urticaria and exanthema may occur. In children sleep disturbances and disturbances of behavioural effects have been observed. Potentially serious hypokalaemia may result from β2-agonist therapy.
Although no teratogenic effects have been observed in animals or in patients, Terbutaline should only be administered with caution during the first trimester of pregnancy. Terbutaline is secreted via breast milk, but effect on the infant is unlikely at therapeutic doses.
Care should be taken with patients suffering from myocardial insufficiency or thyrotoxicosis. Due to the hyperglycaemic effects of β2-stimulants, additional blood glucose measurements are initially recommended when Terbutaline therapy is commenced in diabetic patients. If a previously effective dosage regimen no longer gives the same symptomatic relief the patient should seek further medical advice, for reassessment of asthma therapy, as soon as possible. Potentially serious hypokalaemia may result from β2-agonist therapy. Particular caution is advised in severe asthma as this effect may be potentiated by concomitant treatment with xanthine derivatives, steroids, diuretics and by hypoxia. It is recommended that serum potassium levels are monitored in such situations. Due to the positive inotropic effect of β2-agonists, these drugs should not be used in patients with hypertophic cardiomyopathy.
Possible symptoms: Headache, anxiety, tremor, tonic cramp, palpitations, arrhythmia. A fall in blood pressure sometimes occurs.
Treatment:
Mild and moderate cases: Reduce the dose.
Severe cases: Gastric lavage, administration of activated charcoal.
