Codeine (methyl morphine) is an opioid medication typically taken in pill or liquid form. It is in the same class as other narcotics such as morphine (from which codeine is derived) and heroin.
As a medication, codeine is often used to treat chronic pain from cancer and other serious illnesses. It’s also sometimes used to treat chronic cough, often mixed with other medications such as a decongestant or expectorant. 1,2
Codeine may be effective in treating nighttime restless leg syndrome, especially if symptoms aren’t relieved by other drugs. It has also been found to be effective in treating persistent diarrhea as a result or symptom of serious illness.2
As a prescription opioid, codeine is one of several prescription medications (along with oxycodone, hydrocodone, morphine and others) that has contributed to a significant rise in opioid abuse and overdose deaths over the last decade. From 2004 to 2016, there were over 40,000 codeine-related adverse drug events reported to the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS), resulting in just over 7,200 deaths.3 Although not as deadly as oxycodone, hydrocodone and fentanyl, the number of deaths resulting from codeine use is still significant.3
The United States Drug Enforcement Agency has classified codeine as a Schedule II drug, meaning that it has high potential for abuse and addiction, and it can only be legally obtained with a prescription from a physician.4 However, drugs containing less than 90 mg of codeine are classified as Schedule III drugs, suggesting a lower potential for addiction and abuse but still needing a prescription.4
How Codeine Affects the Brain
As a narcotic medication, codeine’s mechanism of action is similar to other opioid drugs like morphine. It binds to receptors in the brain that are specialized receptors for endogenous opioid-like neurotransmitters. These particular neurotransmitters are involved in controlling pain and reducing the sensation of fatigue. Along with dopamine-facilitated neurotransmitters in the brain that are abundant in areas associated with reward and reinforcement, they produce feelings of euphoria, relaxation, and a sense of the general overall wellbeing. The reinforcing effects of opioid drug use contribute primarily to their potential for leading to abuse and addiction.2,5
Potential Adverse Reactions to Codeine
Potential adverse reactions to codeine include:2
- Itchy skin.
- Difficulty or painful urination.
- Stomach pain.
- Abdominal cramps.
- Decreased libido.
- Other changes in mood.
More serious potential side effects include:2
- Confusion or other mental status changes.
- Difficulties with breathing or swallowing.
- Changes in heartbeat such as fast, irregular, or even pounding heartbeat.
- Seizures or convulsions.
- Changes in vision.
- Extreme lethargy or sleepiness.
- Rashes or hives that may represent allergic reactions.
Indications of overdose include:2
- Clammy or cold skin.
- Extremely slowed breathing or extreme difficulty breathing (respiratory depression).
- Extremely decreased heart rate.
- A loss of muscle tone.
- Clammy or cold skin.
- Unconsciousness and coma.
Other potential serious side effects from long-term codeine use are its potential to result in physical dependence and/or the development of a substance use disorder.
Causes of Codeine Addiction
At this time, there are no definitive causes to explain the development of a substance use disorder to any particular drug or in any particular individual. Research indicates that the development of substance use disorders is caused by a combination of factors that include the person’s genetic makeup, family history, psychological history, experiences, peer group, and a number of other potential factors.6
However, drugs that typically are capable of inducing physical dependence are also drugs that are believed to have a high potential for addiction. The reason for this is that the withdrawal syndrome associated with these drugs makes it particularly difficult for individuals to stop using the drug on their own, and when they experience withdrawal symptoms the quickest way for them to address these symptoms is to take more of the drug. Continuing to take more and more of a drug in spite of negative consequences is a hallmark of addictive behavior.5
Signs of Addiction to Codeine
Some general signs of codeine addiction include:7
- Cravings for codeine.
- Losing interest in activities that used to be interesting and engaging.
- Taking larger doses of codeine than prescribed or taking the drug more frequently than prescribed.
- Obtaining codeine illegally.
- Taking codeine for reasons other than its normal intended use, such as to cope with everyday activities or to feel good.
- Sudden changes in mood.
- Continuing to use codeine in spite of experiencing negative consequences.
- Experiencing a decline in performance at work or school.
- Having relationship problems as a result of codeine use.
- Spending more and more time obtaining codeine or recovering from its use.
- Unsuccessful attempts to quit use of the drug.
- Missing important commitments as a result of use or intoxication.
- Expressing a desire to quit using codeine but not being able to.
- Getting angry when confronted about use of the drug.
- Coming to work or attending family functions while under the influence of the drug.
- Changes in physical appearance that include being disheveled or lax in one’s grooming habits.
Treatment for Codeine Addiction
Codeine is a narcotic medication. It’s a short-acting opioid that’s chemically similar to heroin and produces similar effects in the body, including tolerance and physical dependency, which can lead to addiction.8,9 Like other opioids, it can induce some fairly powerful withdrawal effects.
For people who have developed physical dependence to codeine, withdrawal begins within 8-24 hours of last use and lasts approximately 4-10 days. Withdrawal symptoms may include:8,9
- Nausea, vomiting and diarrhea.
- Insomnia and sleep problems.
- Hot and cold flashes, including goosebumps.
- Muscle cramps.
- Increased irritability.
Effective treatment of an opioid use disorder employs both the use of medications and behavioral therapy.7,8 Prescription medication such as methadone, buprenorphine and naltrexone can help reduce uncomfortable withdrawal symptoms, particularly cravings—which helps to prevent relapse.7 Depending on a person’s level of withdrawal severity and the support they’ll need to recover from their addiction to codeine, withdrawal management may be performed in either inpatient or outpatient addiction treatment programs.10
Inpatient treatment programs allow for closely supervised withdrawal by medical professionals as well as a multidisciplinary team that can cover different aspects of recovery. It also provides a safe environment for recovery and facilitates interactions with other people who are in recovery. This allows for both individual and group therapy sessions, which may help prevent relapse.10
Mutual-help groups, such as those held by 12-step programs like Narcotics Anonymous, offer a structured program built around social support that may be helpful throughout an individual’s recovery from codeine addiction.10 They are free and easy to access, with meetings available in nearly every city at nearly every time of day.
- Hamilton, R. (2017). Tarascon Pharmacopoeia, 18th Edition. Burlington, Mass: Jones & Bartlett Learning.
- Peechakara, B.V. & Gupta M. (2019). StatPearls: Codeine.
- Veronin, M. A., Schumaker, R. P., Dixit, R. R., & Elath, H. (2019). Opioids and frequency counts in the US Food and Drug Administration Adverse Event Reporting System (FAERS) database: A quantitative view of the epidemic. Drug, Healthcare and Patient Safety, 11, 65–70.
- Drug Enforcement Agency. (2019). Controlled Substance Schedules.
- National Institute on Drug Abuse. (2017). The Neurobiology of Drug Addiction.
- National Institute on Drug Abuse. (2018). Drug Misuse and Addiction.
- Diagnostic and statistical manual of mental disorders: DSM-5. (5th ed.). (2013). Washington, D.C.: American Psychiatric Association.
- National Institute on Drug Abuse. (2019). Drug Facts: Prescription Opioids.
- World Health Organization. (2009). Clinical Guidelines for Withdrawal Management and Treatment of Drug Dependence in Closed Settings.
- American Society of Addiction Medicine. (2015). The ASAM National Practice Guideline for the Use of Medications in the Treatment of Addiction Involving Opioid Use.