Salbutamol is a direct-acting sympathomimetic with predominantly beta-adrenergic activity and a selective action on beta2 receptors (a beta2 agonist). This results in its bronchodilating action being more prominent than its effect on the heart.
Bromhexine is a mucolytic used in the treatment of respiratory disorders associated with productive cough.
Guaifenesin is reported to increase the volume and reduce the viscosity of tenacious sputum and is used as an expectorant.
Menthol is chiefly used to relieve symptoms of bronchitis, sinusitis, and similar conditions. For this purpose it may be used as an inhalation, usually with benzoin or eucalyptus oil, as pastilles, or as an ointment with camphor and eucalyptus oil for application to the chest or nostrils.
Salbutamol is readily absorbed from the gastrointestinal tract. It is subject to first-pass metabolism in the liver and possibly in the gut wall; the main metabolite is an inactive sulfate conjugate. Salbutamol is rapidly excreted in the urine as metabolites and unchanged drug; there is some excretion in the faeces. Salbutamol does not appear to be metabolised in the lung, therefore its ultimate metabolism and excretion following inhalation depends upon the delivery method used, which determines the proportion of inhaled salbutamol relative to the proportion inadvertently swallowed. It has been suggested that the majority of an inhaled dose is swallowed and absorbed from the gut. The plasma half-life of salbutamol has been estimated to range from 4 to 6 hours.
Bromhexine hydrochloride is rapidly absorbed from the gastrointestinal tract and undergoes extensive first-pass metabolism in the liver
It is widely distributed to body tissues. About 85 to 90% of a dose is excreted in the urine mainly as metabolites.
Bromhexine is highly bound to plasma proteins. It has a terminal elimination half-life of up to about 12 hours. Bromhexine crosses the blood-brain barrier and small amounts cross the placenta.
Guaifenesin is absorbed from the gastro-intestinal tract. It is metabolised and excreted in the urine.
After absorption, menthol is excreted in the urine and bile as a glucuronide.