Cough & Cold Agents

The cough-and-cold aisle is best understood by what each agent does. Antitussives suppress a cough — dextromethorphan (OTC) acts centrally; codeine is an opioid antitussive; benzonatate numbs airway stretch receptors. Expectorants — guaifenesin — thin and loosen mucus so it’s easier to cough up (they don’t suppress the cough). Decongestants — pseudoephedrine, phenylephrine — are sympathomimetics that constrict swollen nasal vessels to relieve stuffiness (the FDA has stated that oral phenylephrine is ineffective as a decongestant). And mucolytics — acetylcysteine — break apart thick mucus (and, notably, acetylcysteine is also the antidote for acetaminophen overdose).

The clinical judgment is matching the agent to the symptom: suppress a dry, exhausting cough, but don’t suppress a productive cough that’s clearing infection — there, thin the mucus instead.

Decongestants are sympathomimetics, so they can raise blood pressure and heart rate, cause insomnia and jitteriness, and are cautioned in hypertension, heart disease, and hyperthyroidism. Because pseudoephedrine is used to make methamphetamine, it is kept behind the pharmacy counter. Dextromethorphan is serotonergic, so combined with MAOIs, SSRIs/SNRIs it can cause serotonin syndrome, and it is a common drug of abuse ("robotripping") at high doses.

Two more points: codeine antitussive carries opioid risks (sedation, constipation, pediatric caution), and multi-symptom "cold" combination products often contain acetaminophen — a hidden source of overdose if stacked with other products.