Salbutamol is a selective short acting B2 – adrenergic receptor agonist used for acute episodes of bronchospasm caused by bronchopulmonary disorders. The World Health Organization (WHO) ranks salbutamol as one of the most effective and safest medicines essential to healthcare systems.⁵ B2 receptors [bronchodilator receptors] are found in ASM in the respiratory tract. Salbutamol, a B2-andrenergic receptor agonist binds to the B2 receptor, which activates additional cyclase, resulting in the conversion of ATP to cyclic AMP (cAMP). cAMP triggers a cascade of intracellular interactions which inhibit the contraction of bronchial smooth muscle. Therapeutic effect is smooth muscle, relaxation, bronchodilation, and opening of the airways.⁵ Salbutamol also inhibits the release of bronchoconstrictor mediators from mast cells and enhances mucociliary clearance and reduces bronchial oedema.^2,5

Bromhexine’s mechanism of action: Bromhexine is a mucoactive agent. The action of bromhexine influences mucus production, sputum quality and quantity, ciliary activity, and cough severity and frequency.⁶ Bromhexine works on the mucus-producing cells (Goblet cells) and enhances hydrolysis; the chemical breakdown of mucopolysaccharide polymers. The increase in serous mucus in the respiratory tract makes the phlegm thinner and decreases mucus viscosity. This contributes to its secretomotoric effect, which allows the cilia to transport the phlegm out of the lungs easily. This clears mucus from the respiratory tract.

• a) In patients treated with bromhexine, the fibre content in sputum is reduced (mucopolysaccharide fibres and glycoprotein fibres) - this is believed to reduce the viscosity of sputum.⁶
• b) Various clinical studies have demonstrated that bromhexine influences cough. Bromhexine has demonstrated a reduction in expectoration and reduced severity and frequency of cough.⁶

Therefore, by opening up the airways, oral bronchodilators help relieve symptoms such as cough, wheezing and shortness of breath. Mucolytics, on the other hand, break down sputum produced in the lungs, reducing its viscosity and making it easier to expectorate.² A bronchodilator mucolytic combination treatment could be useful in respiratory conditions presenting with tight chest and productive cough.² 

REFERENCES:

1. Shankar S, Chandrashekharan S, Bolmall CS, Baliga V. Efficacy, safety and tolerability of salbutamol + guaiphenesin + bromhexine (Ascoril) expectorant versus expectorants containing salbutamol and either guaiphenesin or bromhexine in productive cough: a randomised controlled comparative study. J Indian Med Assoc. 2010 May;108(5):313-4, 316-8, 320.
2. Schellack N, Mokoena T Grobbelaar S, Du Toit J, Thom L, Kandiwa R.T. Changes in terminology and management of over-the-counter cough therapy – time for a fresh perspective? SA Pharmaceutical Journal.2019 86, No. 3.
3. Rogers DF. Physiology of airway mucus secretion and pathophysiology of hypersecretion. Respir Care. 2007 Sep;52(9):1134-46; discussion 1146-9.
4. Bacsi A, Pan L, Ba X, Boldogh I. Pathophysiology of bronchoconstriction: role of oxidatively damaged DNA repair. Curr Opin Allergy Clin Immunol. 2016 Feb;16(1):59-67.
5. Marques L, Vale N. Salbutamol in the Management of Asthma: A Review. Int J Mol Sci. 2022 Nov 17;23(22):14207.
6. Zanasi A, Mazzolini M, Kantar A. A reappraisal of the mucoactive activity and clinical efficacy of bromhexine. Multidisciplinary Respiratory Medicine 2017 12:7.
7. Girod S, Zahm JM, Plotkowski C, Beck G, Puchelle E. Role of the physicochemical properties of mucus in the protection of the respiratory epithelium. Eur Resplr J 1992, 5, 477-487.