Formoterol
Formoterol is a long-acting beta-2 agonist used in asthma and chronic obstructive pulmonary disease, with a relatively rapid onset of bronchodilation and a duration of approximately twelve hours per dose, supporting twice-daily inhaled administration.
- Chemical formula
- C19H24N2O4
- CAS number
- 73573-87-2
- ATC code
- R03AC13
- Molecular weight
- 344.41 g/mol
- Drug class
- Long-acting beta-2 agonist (LABA)
- Also known as
- Eformoterol, Formoterol
What is it?
Formoterol is a long-acting beta-2 agonist developed in the 1980s. It is supplied as dry powder inhalers, metered-dose inhalers and nebuliser solution, often as a fixed-dose combination with an inhaled corticosteroid such as budesonide or beclometasone. Formoterol has the unusual feature among LABAs of a relatively rapid onset, comparable to short-acting agents, while maintaining a long duration of action.
Mechanism of action
Formoterol selectively activates beta-2 adrenergic receptors on airway smooth muscle, producing bronchodilation through cyclic AMP-mediated relaxation. Unlike salmeterol, formoterol exhibits both rapid receptor binding and sustained partitioning in the lipid membrane, resulting in fast onset (within five minutes) and a duration of action of approximately twelve hours. Reduced release of inflammatory mediators may also contribute to its clinical effect.
Pharmacokinetics
After inhalation, only a small fraction of the dose enters systemic circulation. Bioavailability after inhalation is approximately 60% of the lung-deposited dose. Plasma protein binding is about 50%. Formoterol is metabolised by glucuronidation and O-demethylation to inactive metabolites and excreted in urine and faeces. The terminal half-life is approximately ten hours. Hepatic and renal impairment do not generally require dose adjustment, but caution applies in severe disease.
Indications
Formoterol is approved as maintenance therapy in asthma in combination with an inhaled corticosteroid, and in chronic obstructive pulmonary disease alone or in combination. In asthma, it is also licensed as part of single-inhaler maintenance and reliever therapy with budesonide or beclometasone. According to international guidelines, LABAs should not be used as monotherapy in asthma because of safety concerns; they must be combined with an inhaled corticosteroid.
Safety profile
Common adverse effects include tremor, palpitations, headache, nervousness and throat irritation. Hypokalaemia can occur with high-dose use, particularly when combined with corticosteroids or diuretics. Tachycardia, arrhythmias and ischaemic chest pain have been reported in susceptible patients. According to the prescribing information and regulatory communications, LABAs should always be used with an inhaled corticosteroid in asthma, and the medical history must be reviewed by a clinician before any prescription.
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Frequently asked questions
How is formoterol different from salmeterol? ▾
Both are long-acting beta-2 agonists with approximately twelve-hour duration, but formoterol has a faster onset of bronchodilation, within five minutes, similar to short-acting beta-2 agonists, while salmeterol has a slower onset of about thirty minutes. This rapid onset allows formoterol to be used as part of single-inhaler maintenance and reliever asthma therapy. According to international guidelines, the choice between LABAs is made by the prescriber based on the clinical context.
Why is formoterol always combined with an inhaled corticosteroid in asthma? ▾
LABA monotherapy in asthma has been associated with an increased risk of severe exacerbations and asthma-related mortality. International guidelines and regulatory agencies therefore recommend that formoterol and other LABAs be used in asthma only in combination with an inhaled corticosteroid, ideally in a single combined inhaler to ensure adherence. According to the prescribing information, this rule does not apply to COPD, where LABAs alone are accepted.
What is single-inhaler maintenance and reliever therapy? ▾
In single-inhaler maintenance and reliever therapy (sometimes called MART or AIR), an inhaled corticosteroid combined with formoterol or beclometasone is used both as scheduled controller and as needed for symptoms. The rapid onset of formoterol enables this dual role. According to international guidelines, this approach can reduce severe exacerbations in selected adults and adolescents with persistent asthma when the prescriber considers it appropriate.
Are there cardiac risks with formoterol? ▾
At standard inhaled doses, formoterol is generally well tolerated, but high doses or combination with other sympathomimetics can cause palpitations, tachycardia and arrhythmias. Caution is required in ischaemic heart disease, severe hypertension, hyperthyroidism and hypokalaemia. According to the prescribing information, the medical history and current medication list must be reviewed by a clinician before any prescription.
What are the main contraindications for formoterol? ▾
Formoterol is contraindicated in known hypersensitivity to the molecule or its excipients. Caution is required in tachyarrhythmias, severe ischaemic heart disease, hyperthyroidism, severe hypertension and hypokalaemia, and during pregnancy and breastfeeding. According to international guidelines, formoterol must not be used as monotherapy in asthma. The prescriber should review concomitant medications, especially other sympathomimetics, beta-blockers and diuretics.
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