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# Cough and cold medicines

Antitussives that quiet the cough reflex and expectorants that loosen mucus. They ease symptoms of the common cold but do not shorten it.

Updated Nov 1, 2026

## What they are

Cough and cold medicines include central antitussives (dextromethorphan, codeine), a peripheral antitussive (benzonatate) and an expectorant (guaifenesin), often sold in combinations with antihistamines, decongestants and analgesics. Evidence of benefit is modest. Their main safety issues are in children: over-the-counter cough and cold products are not given to very young children, and in the United States prescription cough medicines containing codeine or hydrocodone are limited to adults because of the risk of slowed breathing, especially in ultrarapid CYP2D6 metabolisers. Combination products also risk accidental double dosing of the same ingredient.

## Mechanism of action

Central antitussives raise the threshold of the cough centre in the medulla: dextromethorphan through NMDA-receptor and sigma-1 actions, codeine through mu-opioid receptors after conversion to morphine by CYP2D6. Benzonatate is chemically related to ester local anaesthetics and numbs the stretch receptors of the airways, lungs and pleura. Guaifenesin is thought to increase the volume and reduce the stickiness of airway secretions so that cough clears them more easily.

Target: Medullary cough centre (central antitussives), airway stretch receptors (benzonatate), airway secretions (expectorants)

## Key points

- Codeine for cough in children: in the United States, prescription opioid cough and cold medicines are limited to adults 18 and older; CYP2D6 ultrarapid metabolisers can form dangerous amounts of morphine.
- Over-the-counter cough and cold products are not given to children under 2, and labels say not to use them under 4.
- Dextromethorphan with an MAO inhibitor (or within two weeks of stopping one) can cause serotonin syndrome; high doses are misused for dissociative effects.
- Benzonatate capsules are swallowed whole: chewing numbs the mouth and throat and can cause choking; accidental ingestion has killed young children.
- Cough lasting weeks needs a diagnosis (asthma, reflux, ACE inhibitor, tuberculosis, pertussis), not just a suppressant.

## Drugs in this class

- [**Dextromethorphan** A non-opioid cough suppressant in many cold products; dangerous with MAO inhibitors and misused at high doses. NMDA glutamate receptor and sigma-1 receptor (cough centre)](https://durgical.com/en/pharmacology/dextromethorphan/)
- [**Benzonatate** A peripheral cough suppressant related to local anaesthetics; capsules are swallowed whole and kept away from children. Stretch receptors of the airways, lungs and pleura](https://durgical.com/en/pharmacology/benzonatate/)
- [**Guaifenesin** An expectorant that thins mucus so it is easier to cough up; it relieves chest congestion but does not treat the cause. Airway secretions (expectorant action)](https://durgical.com/en/pharmacology/guaifenesin/)

## Others in the class

- Codeine (opioid antitussive)
- Hydrocodone (opioid antitussive)
- Ambroxol
- Bromhexine
- Acetylcysteine (mucolytic)

## Test yourself

Think of the answer, then tap the question to see it.

## Why is codeine for cough avoided in children?

Ultrarapid CYP2D6 metabolisers convert it to large amounts of morphine, risking slowed or stopped breathing; US labels limit opioid cough medicines to adults.

## Where does benzonatate act to suppress cough?

Peripherally, on stretch receptors in the airways, lungs and pleura, like a local anaesthetic.

## Which interaction of dextromethorphan is most dangerous?

With MAO inhibitors (and other serotonergic drugs): serotonin syndrome.

## What does an expectorant such as guaifenesin aim to do?

Make airway secretions thinner and easier to cough up; it does not suppress cough.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Codeine Information | FDA](https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/codeine-information) (U.S. Food and Drug Administration, 2023); [Use Caution When Giving Cough and Cold Products to Kids | FDA](https://www.fda.gov/drugs/safe-use-over-counter-otc-medicines-children/use-caution-when-giving-cough-and-cold-products-kids) (U.S. Food and Drug Administration, 2026); [Dextromethorphan: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682492.html) (MedlinePlus (U.S. National Library of Medicine), 2022); [DailyMed - BENZONATATE capsule](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=55b64aee-d4c4-4aad-9016-0dd879e979e6) (DailyMed (U.S. National Library of Medicine), 2026).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/cough-and-cold-medicines/