Codeine is an opioid historically used in medicine as both a pain reliever and a cough suppressant, known scientifically as an antitussive. It was once a common ingredient in many over-the-counter cough syrups. While codeine has not been entirely removed from the marketplace, its status in cough medicine has undergone a dramatic transformation due to increasing concerns about safety and misuse.
Codeine’s Function as a Cough Suppressant
Codeine acts as a narcotic antitussive by affecting the central nervous system to quiet the cough reflex. Its primary action occurs in the brain stem, specifically targeting the cough center located in the medulla oblongata. By binding to mu-opioid receptors, codeine raises the cough threshold, meaning a stronger stimulus is required to trigger a coughing fit. This mechanism effectively reduces the frequency and intensity of coughing episodes, making it useful for managing dry, irritating coughs.
To exert its full effect, the body must first metabolize codeine into its active form, morphine, primarily through the liver enzyme CYP2D6. Variations in the CYP2D6 gene mean some individuals convert codeine into morphine very rapidly, while others convert it slowly. Codeine is considered a potent cough suppressant, though studies have sometimes shown its efficacy is not significantly better than certain non-opioid alternatives.
The Shift from Over-the-Counter Access
The shift away from over-the-counter codeine was driven by public health and safety concerns, especially regarding misuse and risks to vulnerable populations. As an opioid, codeine carries a risk of dependence, abuse, and diversion, prompting regulatory bodies to reassess its accessibility. The growing opioid crisis further highlighted the dangers of keeping such a substance readily available outside of a controlled medical environment.
A major factor in the regulatory change was the severe risk codeine poses to children under 12 years old. The variability in the CYP2D6 enzyme means that children who are “ultra-rapid metabolizers” can quickly convert a standard dose of codeine into dangerously high levels of morphine. This rapid conversion significantly increases the risk of life-threatening respiratory depression, which is slowed and difficult breathing.
In response, the U.S. Food and Drug Administration (FDA) issued stronger warnings in 2017, contraindicating the use of codeine for pain or cough in children younger than 12 years. This was followed by a 2018 action that limited the use of prescription codeine and hydrocodone cough and cold medicines to adults 18 years and older. Similar regulatory actions, often called “up-scheduling,” have been taken in other major jurisdictions, including Australia, Canada, and countries within the European Union, which removed over-the-counter codeine products entirely.
Current Legal Status and Availability
Codeine-containing cough syrup is still available, but its legal status has been altered significantly, transitioning it to a controlled substance. In the United States, codeine cough preparations are generally classified under the Controlled Substances Act, usually as a Schedule V medication. This scheduling applies to products containing limited quantities of the narcotic, such as those with not more than 200 milligrams of codeine per 100 milliliters.
The Schedule V classification means these products are strictly prescription-only and require physician oversight for dispensing. The FDA’s 2018 requirement limits the use of all prescription opioid-containing cough and cold medicines, including those with codeine, to individuals 18 years of age and older. This means a prescription for codeine cough syrup cannot be written for anyone under the age of eighteen.
The global trend has been toward stricter control, with many countries moving all codeine products to prescription-only status to combat misuse. For most consumers, codeine cough syrup is no longer found in the over-the-counter aisle, and obtaining it requires a doctor’s evaluation and prescription.
Effective Non-Codeine Treatments
Due to the restrictions on codeine, several non-opioid medications have become the standard for treating cough symptoms. The most common over-the-counter cough suppressant is dextromethorphan (DM), which acts on the brain’s cough center but is not an opioid. Dextromethorphan is widely available in many liquid and tablet cold and flu preparations.
Another pharmacological alternative is guaifenesin, classified as an expectorant rather than a suppressant. Guaifenesin works by thinning bronchial secretions, making a productive cough more effective at clearing mucus from the airways. For soothing a dry cough, simple non-pharmacological remedies are often recommended. Staying well-hydrated and using a humidifier can help soothe irritated airways, and a spoonful of honey has also been shown to help relieve cough symptoms.