• Dextromethorphan (10mg) is a cough suppressant (antitussive) that works by affecting the signals in the brain that trigger the cough reflex. It is effective in reducing the urge to cough, especially when it is non-productive or dry.
• Chlorpheniramine (4mg) is an antihistamine that helps relieve symptoms of allergies, such as sneezing, runny nose, and itching, by blocking histamine receptors. It also has mild sedative properties, which can help provide relief from discomfort caused by allergic reactions or cold symptoms.

This combination is effective for treating symptoms associated with colds, allergic rhinitis, and upper respiratory tract infections, providing relief from both coughing and allergy-related symptoms. However, it may cause drowsiness due to the sedative effects of chlorpheniramine, so it should be used with caution, especially when performing tasks that require alertness, such as driving.