Bromhexine is an expectorant/mucolytic agent. Terbutaline is used for the prevention and reversal of bronchospasm in patients 12 years of age and older with reversible, obstructive airway disease, as well as symptomatic management of reversible bronchospasm associated with bronchitis and emphysema. Guaifenesin elicits an action to facilitate productive cough to manage chest congestion. Menthol mediates anaesthetic properties and anti-irritating properties locally, thus it is widely used to relieve minor throat irritations.

Indications:
● Cough
● Asthma
● Chest Tightness

Mechanism:

Bromhexine:
is a mucolytic drug used in the treatment of respiratory disorders associated with viscid or excessive mucus. Bromhexine is intended to support the body's mechanisms for clearing mucus from the respiratory tract. It is secretolytic, increasing the production of serous mucus in the respiratory tract, which makes the phlegm thinner and less viscous. This contributes to a secretomotoric effect, allowing the cilia to more easily transport the phlegm out of the lungs. For this reason it is often added to cough syrups. It has been shown to increase the proportion of serous bronchial secretion, making it more easily expectorated. It is indicated as "secretolytic therapy in bronchopulmonary diseases associated with abnormal mucus secretion and impaired mucus transport".
Bromhexine is rapidly absorbed, with peak plasma levels being reached within 1 h. As it is lipophilic, it is rapidly redistributed, undergoes extensive hepatic metabolism. About 85 to 90% of a dose is excreted in the urine mainly as metabolites. 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.

Terbutaline:
is a relatively selective beta2-adrenergic bronchodilator that has little or no effect on alpha-adrenergic receptors. Terbutaline appears to have a greater stimulating effect on beta-receptors of the bronchial, vascular, and uterine smooth muscles (beta2 receptors) than on the beta-receptors of the heart (beta1 receptors). This drug relaxes smooth muscle and inhibits uterine contractions, but may also cause some cardio stimulatory effects and CNS stimulation.
Only 30-50% of the drug is absorbed orally. It is mainly excreted in urine with a half-life of 5.5-5.9 hours.

Guaiphenesin:
is categorized as an expectorant that acts by enhancing the output of phlegm (sputum) and bronchial secretions via decreasing the adhesiveness and surface tension of such material. It may also act as an irritant to gastric vagal receptors, and recruit efferent parasympathetic reflexes that can elicit glandular exocytosis that is comprised of a less viscous mucus mixture.
It is well orally absorbed and volume of distribution is 116L. It is metabolised in liver and is excreted in urine. The half-life is approximately 1 hour.

Menthol:
primarily activates the cold-sensitive TRPM8 receptors in the skin. Menthol, after topical application, causes a feeling of coolness due to stimulation of 'cold' receptors by inhibiting Ca++ currents of neuronal membranes. It may also yield analgesic properties via kappa-opioid receptor agonism.

Side Effects:
● Stomach upset
● Decreased appetite
● Severe nausea
● Vomiting
● Dizziness or headache
● Rash

Interactions:
● Guaiphenesin may interact with duloxetine, phenylephrine and albuterol
● Terbutaline may interact with beta-blockers, such as atenolol, carteolol, labetalol, metoprolol, nadolol, propranolol, sotalol, carvedilol, timolol and certain diuretics

Contraindications:
● Not be administered in patients with hypersensitive to sympathomimetic amines
● In patients with known idiosyncratic reaction to bromhexine hydrochloride