Hypokalaemia: Potentially serious hypokalaemia may result from β2-agonist therapy. Particular caution is recommended in acute severe asthma as the associated risk may be augmented by hypoxia. The hypokalaemic effect may be potentiated by concomitant treatments (see Interactions). It is recommended that serum potassium levels are monitored in such situations.
Cardiovascular Diseases and Hyperthyroidism: Caution is advised when terbutaline is administered to patients with thyrotoxicosis.
Diabetes: Due to the hyperglycaemic effects of β2-stimulants, additional blood glucose controls are initially recommended when diabetic patients are commenced on terbutaline.
Terbutaline sulphate has not been approved for and should not be used for acute or maintenance tocolysis (beyond 48-72 hrs). In particular, terbutaline sulphate should not be used for maintenance tocolysis in the outpaitent or home setting.
Patients with chronic asthma who require maintenance therapy with β2-agonists must also have optimal anti-inflammatory treatment with corticosteroids. These patients should be advised to continue taking their anti-inflammatory treatment after starting Bricanyl controlled release tablets even when symptoms reduce. If the symptoms persist or if treatment with β2 agonists needs to be increased, this indicates a worsening in the underlying condition and justifies reassessment of the treatment.
Turbuhaler/Injection: Cardiovascular effects may be seen with sympathomimetic drugs, including Bricanyl. There is some evidence from post-marketing data and published literature of rare occurrences of myocardial ischaemia associated with β-agonists. Patients with underlying severe heart disease (eg, ischaemic heart disease, arrhythmia or severe heart failure) who are receiving Bricanyl, should be warned to seek medical advice if they experience chest pain or other symptoms of worsening heart disease. Attention should be paid to assessment of symptoms eg, dyspnoea and chest pain, as they may be of either respiratory or cardiac origin.
Arrhythmogenic Potential: β2-stimulants have an arrhythmogenic potential which must be considered for each patient when receiving treatment for bronchospasm.
Sensitivity to Sympathomimetic Amines: Some patients may be unusually sensitive to β-adrenergic stimulants. Terbutaline should be used with caution when an increased susceptibility to sympathomimetic amines can be expected for instance in other patients with hyperthyroidism not yet adequately controlled.
Pulmonary Conditions: Positive pressure delivery system (IPPB) for respiratory drugs should not be used in pulmonary conditions involving pneumothorax, air cyst or mediastinal emphysema unless special drainage is carried out.
Lack of Response: If the usual dose does not provide the usual relief, a nonresponsive state may be developing. If a previously effective dose lasts less than usual, patients should be instructed to consult a doctor. This could also be the sign of worsening asthma and repeated inhalations of β2-antagonists must then not then delay reassessment of the asthma therapy.
Acute Asthma: If patients with an acute attack of asthma fail to respond to a dry powder inhaler of β2-agonist, they should be advised to follow their personal asthma action plan. Failure to respond to β2-agonists in general can be due to various reasons related to drug administration or the disease itself. Particularly in children ≤5 years and exceptionally in other cases, inspiratory flow through a dry powder inhaler may not be sufficient for optimal drug delivery. If a nonresponse occurs, medical help should be sought while a β2-agonist treatment is continued. In such a situation and if available, a pressurised metered-dose inhaler with spacer should be used. (See Lack of Response in previous text.)
Cardionecrosis: Animal studies suggest that cardionecrotic lesions may occur with high doses of some sympathomimetic amines. On this evidence, it is not possible to exclude myocardial lesions as a possible hazard resulting from long-term treatment.
Impaired Hepatic Function: Hepatic failure has not been shown to influence the metabolism of terbutaline. However, caution should be exercised in patients with impaired liver function.
Impaired Renal Function: As terbutaline is largely excreted in urine, caution should be exercised in patients with renal impairment.
Effects on the Ability to Drive or Operate Machinery: Bricanyl does not affect the ability to drive or use machines.
Use in pregnancy: Pregnancy Category A: No teratogenic effects have been observed in animals or in patients. However, caution is recommended during the 1st trimester of pregnancy.
Oral β2 agonists with slow release must be used with caution in the final stage of pregnancy because of the tocolytic effect.
During pregnancy, serious adverse reactions, including death, have been reported after administration of terbutaline sufate to pregnant women. In the mother, these adverse reactions include increased heart rate, transient hyperglycaemia, hypokalaemia, cardiac arrhythmias, pulmonary edema, and myocardial ischaemia. Increased fetal heart rate and neonatal hypoglycaemia may occur as a result of maternal administration.
Use in lactation: Terbutaline passes over to breast milk but an influence on the child is unlikely with therapeutic doses.
Although terbutaline is secreted into breast milk, and milk concentrations are approximately those in maternal plasma, 2 individual case studies indicate that the infant is likely to receive 0.2-0.7% of the maternal dose (0.4 mcg/kg/day and 0.7 mcg/kg/day, respectively), depending (for example) on the time of feeding in relation to administration of the drug. In the 4 infants studied, this did not result in any signs of β-adrenoceptor stimulation.
Transient hypoglycaemia has been reported in newborn pre-term infants after maternal β2-agonist treatment.