Formoterol

Formoterol is a long-acting beta-2 agonist with rapid onset (1 to 3 minutes) and 12-hour duration. It is used with an inhaled corticosteroid in asthma, including as an anti-inflammatory reliever, and in COPD.

Classification. Long-acting beta-2 agonist, full agonist.

Mechanism. Moderately lipophilic; rapid receptor activation with sustained effect in the membrane.

Pharmacokinetics. Mostly local action. Hepatic glucuronidation and O-demethylation. Half-life about 10 hours.

First-line, asthma, maintenance and reliever therapy. Budesonide with formoterol (160/4.5 micrograms delivered) 1 to 2 inhalations twice daily as maintenance, plus 1 inhalation as needed for symptoms. Maximum 12 inhalations in 24 hours.

First-line, mild asthma, reliever only. Budesonide with formoterol 1 inhalation as needed.

First-line, COPD. Formoterol 12 micrograms twice daily, or the fixed combination with a long-acting antimuscarinic.

Fixed-dose maintenance. Formoterol 12 micrograms twice daily by dry powder, with a separate or combined inhaled corticosteroid. Maximum 48 micrograms daily.

Children. From 6 years, 12 micrograms twice daily with a corticosteroid.

Titration. Step up by corticosteroid dose first. Step down when control is sustained. No loading dose.

Emergency. Not first-line, although formoterol has a rapid onset.

Boxed-warning-level risk. Asthma-related death when used without an inhaled corticosteroid. Never use as monotherapy in asthma.

Contraindications. Hypersensitivity.

Serious adverse effects. Arrhythmia, QT prolongation, hypokalaemia, hyperglycaemia, paradoxical bronchospasm.

Common adverse effects. Tremor, palpitations, headache.

Interactions. Non-selective beta-blockers; hypokalaemic drugs; QT-prolonging drugs; monoamine oxidase inhibitors.

Common prescribing errors. Formoterol without a corticosteroid. Exceeding 12 inhalations in a day. Confusing delivered and metered dose labels.

Special groups.

• Pregnancy: budesonide with formoterol is acceptable if needed. Breastfeeding: probably compatible.

• Older adults: monitor heart rate.

• Kidney impairment: no adjustment. Liver impairment: caution in severe disease.

• East Africa: the combination is often unavailable or costly; the alternative is a separate inhaled corticosteroid with salbutamol.

Formulations. Dry powder 6 and 12 micrograms/dose; combination inhalers with budesonide or beclometasone.

Technique. Deep, forceful inhalation. Rinse the mouth after combination use.

Baseline. Spirometry, pulse, potassium if risk factors.

Monitoring. Reliever use, exacerbations, spirometry, heart rate.

Stop and reduce rules. Step down when control holds for 3 months. Stop for arrhythmia. Therapeutic drug monitoring is not used.

Referral and escalation. Refer if control fails with high-dose corticosteroid and formoterol.