| Abstract |
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Cough is a natural reflex mechanism that removes foreign materials and secretions from the airways. It is the most common symptom of airway inflammatory diseases. Clinically, cough suppressant drugs are used to relief cough. However, the most frequently used antitussive drugs in clinical practice produce adverse effects like drowsiness, constipation, hypotension and respiratory depression that limit their use. Hence, currently there is unmet need for the development of safe and effective antitussive therapeutic options in the treatment of persistent cough as alternative to existing medications. Medicinal plants, claimed to have antitussive activity from traditional medicine, could be potential sources of alternative therapy. Adhatoda schimperiana (Hochst.) Nees (Family: Acanthaceae) has been used in Ethiopian traditional medicine as a remedy for cough and bronchial asthma. In the present study, antitussive activity of 80% methanol extract of Adhatoda schimperiana leaves at various doses (100, 200 and 400 mg/kg/day, orally for 3 days) were investigated by the classic ammonium hydroxide-induced cough model in mice. The antitussive activity was assessed by the latent period of cough and the percent inhibition of cough frequency compared to that of the negative control (Tween 80) and a standard drug (codeine phosphate, 10 mg/kg). The crude 80% methanol extract of Adhatoda schimperiana leaves showed a statistically significant dose-dependent increase in the latent period of cough (P < 0.05), and reduction in cough frequency (P < 0.05) compared to that of the negative control group. The maximum antitussive activity of the extract was observed at the dose of 400 mg/kg/day which achieved 57.5% cough frequency suppression. However, the antitussive activity was lower in comparison to that of codeine phosphate, the strongest narcotic antitussive agent which achieved 74.0% cough frequency suppression. The findings of this study suggest that Adhatoda schimperiana leaves might be helpful for reducing cough, supporting the claimed traditional use of the plant for the relief of symptoms of respiratory illnesses. Further investigation with activity-guided fractionation is required to elucidate the principal components responsible for the antitussive activity, and to determine the mechanism of action of the active components of the plant. |
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