indication

For the long term, once-daily maintenance bronchodilator treatment of airflow obstruction in patients with chronic obstructive pulmonary disease (COPD), including chronic bronchitis and/or emphysema.

pharmacology

Bronchodilator drugs are the foundation for the treatment of chronic obstructive pulmonary disease. The principal inhaled bronchodilator treatments used are β(2) -agonists and anticholinergics, either alone or in combination. Currently available β(2) -agonists are of either short duration and used multiple times/day, or of long duration, which requires twice-daily administration. Indacaterol is considered an ultra-long-acting β(2) -agonist and was recently approved for use in the United States. Its duration of action is approximately 24 hours, allowing for once-daily administration. Cough was the most commonly reported adverse effect with use of indacaterol. Cough usually occurred within 15 seconds of inhalation of the drug, lasted around 6 seconds, was not associated with bronchospasm, and did not cause discontinuation of the drug. Otherwise, the drug's safety profile was similar to that of other bronchodilators. [PMID: 22499359]

mechanism of action

Indacaterol works by stimulating beta-2 receptors in the smooth muscle of the airways. This causes relaxation of the muscle, thereby increasing the diameter of the airways, which become constricted in asthma and COPD. The pharmacological effects of beta2-adrenoceptor agonist drugs, including indacaterol, are at least in part attributable to stimulation of intracellular adenyl cyclase, the enzyme that catalyzes the conversion of adenosine triphosphate (ATP) to cyclic-3’, 5’-adenosine monophosphate (cyclic monophosphate). Increased cyclic AMP levels cause relaxation of bronchial smooth muscle. In vitro studies have shown that indacaterol has more than 24-fold greater agonist activity at beta2-receptors compared to beta1-receptors and 20-fold greater agonist activity compared to beta3-receptors. This selectivity profile is similar to formoterol. The clinical significance of these findings is unknown.

toxicity

The expected signs and symptoms associated with overdosage of indacaterol are those of excessive beta-adrenergic stimulation and occurrence or exaggeration of any of the signs and symptoms, e.g., angina, hypertension or hypotension, tachycardia, with rates up to 200 bpm, arrhythmias, nervousness, headache, tremor, dry mouth, palpitation, muscle cramps, nausea, dizziness, fatigue, malaise, hypokalemia, hyperglycemia, metabolic acidosis and insomnia. As with all inhaled sympathomimetic medications, cardiac arrest and even death may be associated with an overdose of indacaterol.

biotransformation

After oral administration of radiolabeled indacaterol, unchanged indacaterol was the main component in serum, accounting for about one third of total drug-related AUC over 24 hours. A hydroxylated derivative was the most prominent metabolite in serum. Phenolic O-glucuronides of indacaterol and hydroxylated indacaterol were further prominent metabolites. A diastereomer of the hydroxylated derivative, a N-glucuronide of indacaterol, and C- and N-dealkylated products were further metabolites identified. In vitro investigations indicated that UGT1A1 was the only UGT isoform that metabolized indacaterol to the phenolic O-glucuronide. CYP3A4 is the predominant isoenzyme responsible for hydroxylation of indacaterol.

absorption

The median time to reach peak serum concentrations of indacaterol was approximately 15 minutes after single or repeated inhaled doses. Absolute bioavailability of indacaterol after an inhaled dose was on average 43-45%.

half life

Indacaterol serum concentrations declined in a multi-phasic manner with an average terminal half-life ranging from 45.5 to 126 hours. The effective half-life, calculated from the accumulation of indacaterol after repeated dosing with once daily doses between 75 mcg and 600 mcg ranged from 40 to 56 hours which is consistent with the observed time-to-steady state of approximately 12-15 days.

route of elimination

Renal clearance plays a minor role (about 2 to 6% of systemic clearance) in the elimination of systemically available indacaterol. In a human ADME study where indacaterol was given orally, the fecal route of excretion was dominant over the urinary route. Indacaterol was excreted into human feces primarily as unchanged parent drug (54% of the dose) and, to a lesser extent, hydroxylated indacaterol metabolites (23% of the dose).