Antitussives are medications that suppress or reduce coughing. They're primarily used for dry, nonproductive coughs that don't serve a useful purpose, like clearing mucus. Understanding how these drugs work, their side effects, and key nursing considerations helps keep administration safe.

Mechanisms of Action

Antitussives fall into two categories based on where they act:

Centrally acting antitussives suppress the cough reflex by acting on the cough center in the medulla oblongata. They reduce the brain's sensitivity to cough signals, decreasing the urge to cough.

Codeine and dextromethorphan are the main centrally acting agents.

Peripherally acting antitussives work locally in the airways by decreasing the sensitivity of stretch receptors (cough receptors) in the respiratory tract. They block the afferent impulse before it ever reaches the brain.

Benzonatate is the primary peripherally acting antitussive. It's structurally related to local anesthetics and numbs the stretch receptors in the lungs and pleura.

Mechanisms of action, Frontiers | Coughing in Small Animal Patients

Indications, Effects, and Side Effects

Drug	Indication	Key Effects	Common Side Effects
Codeine	Dry, nonproductive cough	Suppresses cough reflex; also has mild analgesic and sedative properties	Drowsiness, constipation, nausea, vomiting, respiratory depression
Dextromethorphan	Dry, nonproductive cough	Suppresses cough reflex without analgesic or sedative properties	Dizziness, drowsiness, nausea, vomiting
Benzonatate	Dry, nonproductive cough	Decreases sensitivity of peripheral cough receptors; minimal CNS effects	Headache, drowsiness, constipation, numbness of mouth and throat
Guaifenesin	Productive cough with thick, viscous mucus	Acts as an expectorant, not a true antitussive; increases volume and decreases viscosity of secretions to make coughing more effective	Nausea, vomiting, diarrhea, stomach discomfort

A few things to note from this table:

Codeine is an opioid, which is why it carries the risk of respiratory depression and has abuse potential. It's a controlled substance.
Dextromethorphan is the most commonly used OTC antitussive (found in many "DM" cough products). It does not have opioid analgesic effects, but at very high doses it can be abused for dissociative effects.
Benzonatate capsules must be swallowed whole. If chewed or dissolved in the mouth, they cause oropharyngeal numbness that can lead to choking or aspiration.
Guaifenesin is technically an expectorant, not an antitussive. It doesn't suppress cough; it makes a productive cough more effective. You'll often see it combined with antitussives in OTC formulations.

Mechanisms of action, Frontiers | Mechanisms of Action for Antimicrobial Peptides With Antibacterial and Antibiofilm ...

Nursing Considerations

Assessment

Evaluate the type of cough: Is it dry/nonproductive or productive? How long has it lasted, and how frequent is it?
Assess for underlying causes such as respiratory infections, asthma, GERD, or ACE inhibitor use.
Review the patient's full medication history and allergy profile before selecting an antitussive.
A productive cough generally should not be suppressed, since coughing clears secretions from the airway.

Administration

Administer at the prescribed dose and route. Codeine-containing products require careful dose verification due to opioid risks.
For benzonatate, instruct the patient to swallow capsules whole without chewing, sucking, or crushing.
Educate patients on proper use and expected effects.
Screen for drug interactions, particularly with CNS depressants (alcohol, benzodiazepines, opioids, sedating antihistamines). Combining these with centrally acting antitussives increases the risk of excessive sedation and respiratory depression.

Monitoring

Track cough frequency and severity to evaluate whether the medication is working.
Monitor for adverse effects: watch for excessive drowsiness, constipation, and signs of respiratory depression (especially with codeine).
Reassess the need for continued therapy. If the cough persists beyond 7 days, worsens, or new symptoms develop (fever, hemoptysis, dyspnea), the patient needs further evaluation.

Patient Education

Medication instructions

Take the antitussive exactly as prescribed. Do not exceed the recommended dose, even if the cough persists.
Swallow benzonatate capsules whole. Chewing them can numb the throat and increase aspiration risk.
Dextromethorphan products are available OTC, but patients should still follow dosing guidelines and avoid "doubling up" with combination products that contain the same ingredient.

Side effect management

Drowsiness is common with codeine and can occur with other antitussives. Avoid driving or operating machinery until you know how the medication affects you.
For constipation (especially with codeine), increase fluid intake and dietary fiber. A stool softener may be needed.
Report severe or persistent side effects to your healthcare provider promptly.

Drug interactions and precautions

Do not combine antitussives with alcohol or other CNS depressants without provider approval. This combination can cause dangerous sedation or respiratory depression.
Dextromethorphan should not be taken with MAOIs or SSRIs due to the risk of serotonin syndrome, a potentially life-threatening condition.
Always inform your healthcare provider of all medications you're taking, including OTC products and supplements.

Follow-up

Keep track of your cough symptoms and how well the medication is working.
Follow up with your provider if the cough lasts longer than expected, gets worse, or is accompanied by new symptoms like fever, blood-tinged sputum, or difficulty breathing.