Short answer: Codeine is a mild opioid used for pain and, in some products, for cough. The body converts it into morphine, and how fast that happens varies with genetics, which makes codeine dangerous for some people. Plain codeine is Schedule II, combinations with acetaminophen are Schedule III, and low-dose cough syrups are Schedule V.
Key takeaways
- What it is: Codeine is an opioid agonist (prodrug) and a Schedule II controlled substance in the US.
- Main uses: Mild to moderate pain; cough.
- Timing: effects start in 30 to 60 minutes and last 4 to 6 hours.
- Most dangerous mix: Benzodiazepines (alprazolam, diazepam, clonazepam), which can cause profound sedation, slowed breathing, coma, death.
- Naloxone: it reverses an overdose.
- Dependence risk: Moderate.
- Legal route: only with a prescription from a DEA-registered clinician, filled by a licensed pharmacy.
What is codeine?
Codeine is approved for mild to moderately severe pain when non-opioid treatments are not enough, and in combination products to suppress cough in adults.
Codeine itself has little effect. The liver enzyme CYP2D6 converts about 5 to 10% of it into morphine. People who are "ultra-rapid metabolizers" convert it fast and can reach dangerous morphine levels from normal doses, while "poor metabolizers" get little pain relief. The share of ultra-rapid metabolizers varies widely by ancestry.
Quick facts
| Fact | Codeine |
|---|---|
| Generic name | Codeine sulfate or phosphate |
| Brand names | Tylenol with Codeine (No. 3, No. 4); cough products |
| Drug class | Opioid agonist (prodrug converted to morphine) |
| US legal status | Schedule II alone; III with acetaminophen; V in low-dose cough syrups |
| Approved uses | Mild to moderately severe pain; cough (combination products, adults only) |
| Forms | Tablets; tablets with acetaminophen; oral solution; cough syrups |
| Onset | 30 to 60 minutes |
| Half-life | About 3 hours |
| Broken down by | CYP2D6 (to morphine) and CYP3A4 |
How long does codeine last?
- Starts working: 30 to 60 minutes
- Effects last: 4 to 6 hours
- Half-life: About 3 hours
Its half-life is about 3 hours. Urine tests usually detect it for 1 to 2 days.
Timing varies with the dose, the form, how it is taken, liver and kidney function, age, and other drugs taken at the same time.
What are the biggest risks of codeine?
The FDA requires boxed warnings, its strongest, on codeine products, including:
- Codeine exposes users to risks of addiction, misuse, and abuse, which can lead to overdose and death.
- Life-threatening slowed breathing can occur, especially when starting treatment or after a dose increase.
- Accidental ingestion, especially by children, can cause a fatal overdose.
- Use with benzodiazepines or other central nervous system depressants, including alcohol, can cause profound sedation, slowed breathing, coma, and death.
Common side effects include constipation, drowsiness, nausea, lightheadedness, and sweating.
Breastfeeding: the FDA advises against codeine while breastfeeding because babies of ultra-rapid metabolizers have been harmed by morphine in breast milk.
What should you never mix with codeine?
| Combined with | What happens | Label guidance |
|---|---|---|
| Benzodiazepines (alprazolam, diazepam, clonazepam) | Profound sedation, slowed breathing, coma, death | Boxed warning; avoid unless no alternative |
| Alcohol | Stronger sedation and slowed breathing | Avoid |
| Gabapentin, pregabalin, sleep medicines, muscle relaxants | Additive sedation and breathing problems | Use caution; lower doses |
| Fluoxetine, paroxetine, bupropion, quinidine | Block CYP2D6, reducing pain relief; stopping them raises morphine levels | Monitor closely |
| Promethazine (in cough syrups) | Additive sedation | Use caution; misused as "lean" |
| Other opioids | Additive breathing suppression | Avoid unless directed by prescriber |
Check any combination with the DoseUses combination checker or ask a pharmacist.
What are the signs of a codeine overdose, and what should you do?
Codeine overdose causes pinpoint pupils, extreme drowsiness, confusion, and slow or stopped breathing. Ultra-rapid metabolizers, especially children, can overdose on ordinary doses.
If someone may have overdosed
- Call 911 if the person is unresponsive, cannot be woken, has blue or gray lips, or is breathing slowly or not at all.
- Give naloxone (Narcan or a generic nasal spray, sold without a prescription) into one nostril. If there is no response after 2 to 3 minutes, give another dose.
- If you are trained, give rescue breaths. Otherwise place the person on their side so they do not choke.
- Stay with them. Naloxone can wear off before codeine does, so the overdose can return even after the person wakes up.
- Most states have Good Samaritan laws that protect people who call 911 for an overdose from some drug charges.
What is codeine withdrawal like, and how long does it last?
People who take codeine regularly for more than a few weeks become physically dependent, even when they take it exactly as prescribed. Dependence is not the same as addiction, but it means stopping suddenly causes withdrawal.
- 8 to 24 hoursEarly symptomsAnxiety, restlessness, yawning, sweating, runny nose, watery eyes, and muscle aches.
- Days 1 to 3Peak withdrawalDiarrhea, stomach cramps, nausea and vomiting, goosebumps, dilated pupils, fast heartbeat, and strong cravings. Rarely dangerous in healthy adults, but dehydration can be serious.
- Days 5 to 10Lingering symptomsPoor sleep, low mood, low energy, and cravings can continue for weeks. Tolerance falls quickly, which raises the risk of overdose if use restarts.
See the withdrawal timelines and the full codeine withdrawal guide.
Is codeine legal?
In the United States, codeine is a Schedule III controlled substance. The only legal way to get it is with a prescription from a clinician registered with the Drug Enforcement Administration (DEA), filled by a licensed pharmacy. Depending on state law, that can be a physician, nurse practitioner, or physician assistant.
- Refills: a Schedule III prescription can be refilled up to five times within six months of the date it was written. After that, a new prescription is needed.
- Telehealth: federal flexibilities let DEA-registered clinicians prescribe Schedule II to V medicines after a telemedicine visit, without a prior in-person exam, through December 31, 2026. A permanent DEA rule was under final review in late 2026. State rules can be stricter.
- Monitoring: prescribers and pharmacists in most states check a prescription drug monitoring program, a database of controlled-substance prescriptions, before prescribing or dispensing.
Outside the United States
| Country | Status |
|---|---|
| United Kingdom | Class B; low-strength combinations sold in pharmacies |
| Canada | Schedule I; low-dose combinations available from pharmacists in some provinces |
| Australia | Prescription only since 2018 (Schedule 4 or 8 depending on product) |
| International | Schedule II of the 1961 Single Convention |
Frequently asked questions about codeine
Is codeine safe for children?
No. It is contraindicated in children under 12, and in anyone under 18 after tonsil or adenoid surgery, because some children turn codeine into morphine very quickly.
Why does codeine not work for some people?
About 5 to 10% of people of European ancestry are poor CYP2D6 metabolizers and convert little codeine into morphine, so they get little pain relief.
Is codeine cough syrup legal without a prescription?
Federally, low-dose codeine cough syrups are Schedule V. A few states let pharmacists sell them without a prescription, with ID and limits; most require a prescription.
What is "lean"?
A street name for codeine-promethazine cough syrup mixed with soft drinks. The combination causes heavy sedation and has caused fatal overdoses, especially with alcohol.
How long does codeine stay in your system?
Its half-life is about 3 hours. Urine tests usually detect it for 1 to 2 days.
Sources
- Tylenol with Codeine (codeine) prescribing information, DailyMed, US National Library of Medicine.
- FDA restricts use of prescription codeine pain and cough medicines and tramadol pain medicines in children, US Food and Drug Administration, 2017.
- Information about naloxone and nalmefene, US Food and Drug Administration.
- CDC Clinical Practice Guideline for Prescribing Opioids for Pain, 2022, Centers for Disease Control and Prevention, MMWR.
- Controlled Substance Schedules, DEA Diversion Control Division.
- 21 CFR 1306.22, Refilling of prescriptions (Schedules III and IV), Electronic Code of Federal Regulations.
- Prescribing controlled substances via telehealth, US Department of Health and Human Services.
- BeSafeRx: Your Source for Online Pharmacy Information, US Food and Drug Administration.
This guide summarizes the sourced DoseUses Codeine profile, written from FDA labels, DEA rules, and federal health agencies. It is educational and is not medical advice. Last updated October 5, 2026.
