Tylenol 3 is a prescription painkiller that combines 300 mg of acetaminophen with 30 mg of codeine phosphate in each tablet. It belongs to a family of numbered Tylenol-with-codeine products and is used to treat mild to moderate pain. Because it contains an opioid (codeine), it’s classified as a Schedule III controlled substance, meaning you need a prescription to get it.
What’s Inside Each Tablet
The two active ingredients work through different pathways. Acetaminophen, the same pain reliever found in regular Tylenol, reduces pain signals and lowers fever. Codeine is a weaker opioid that your liver converts into morphine in small amounts, which then acts on pain receptors in your brain and spinal cord. The combination provides stronger relief than either ingredient alone.
The “3” refers to the codeine dose. Tylenol No. 2 contains 15 mg of codeine with 300 mg of acetaminophen. Tylenol No. 3 doubles that to 30 mg. Tylenol No. 4 contains 60 mg. All three versions keep the acetaminophen at the same 300 mg level. Tylenol No. 2 and No. 3 also include a small amount of caffeine (15 to 30 mg), roughly the equivalent of a quarter cup of coffee.
Common Side Effects
The most predictable side effects come from the codeine component. Constipation is common enough that doctors often recommend dietary changes or a stool softener alongside the prescription. Nausea, vomiting, sweating, and drowsiness are also frequent. Some people experience decreased sex drive or sexual dysfunction.
More serious reactions require immediate attention. These include extreme drowsiness, confusion, hallucinations, seizures, difficulty breathing or swallowing, unusual snoring or long pauses between breaths during sleep, chest pain, and changes in heartbeat. A severe allergic reaction can cause hives, rash, or swelling of the face, throat, or tongue.
Why Codeine Affects People Differently
Codeine is essentially a prodrug. It doesn’t do much on its own. Your liver has to convert it into morphine using a specific enzyme, and people vary widely in how active that enzyme is. Only about 5 to 10 percent of a codeine dose gets converted to morphine in most people. The rest breaks down into inactive compounds that get excreted.
Some people are “ultrarapid metabolizers,” meaning they carry extra copies of the gene that controls this enzyme. Their bodies convert codeine to morphine faster and more completely, which can produce overdose symptoms, including extreme sleepiness, confusion, and dangerously shallow breathing, even at normal prescribed doses. In some cases, this has been fatal. On the other end of the spectrum, “poor metabolizers” convert very little codeine to morphine and get almost no pain relief from the drug. Pharmacogenomic testing can identify which category you fall into, though it isn’t routinely ordered.
Safety Restrictions for Children
Codeine-containing products, including Tylenol 3, are contraindicated for all children under 12. The FDA issued this restriction after reports of life-threatening breathing problems and deaths in young children who received codeine, particularly after tonsil or adenoid removal surgery. Many of those children turned out to be ultrarapid metabolizers.
For adolescents aged 12 to 18, codeine should be avoided if other risk factors are present, such as obesity, obstructive sleep apnea, severe lung disease, or use of other sedating medications. It is fully contraindicated for post-tonsillectomy or post-adenoidectomy pain in anyone under 18.
Acetaminophen Overdose Risk
Because each Tylenol 3 tablet contains 300 mg of acetaminophen, the total can add up quickly if you’re also taking other acetaminophen-containing products (cold medicines, sleep aids, other painkillers). Exceeding 3,000 to 4,000 mg of acetaminophen in a day risks serious liver damage. At 300 mg per tablet, taking more than 10 to 12 tablets in a day puts you in dangerous territory from acetaminophen alone, separate from the opioid risks.
Acetaminophen overdose can be deceptive. Early symptoms like nausea and loss of appetite may seem mild, but liver damage can progress silently over the following days. The antidote is nearly 100% effective if administered within 8 hours of ingestion, but the window narrows after that. People with existing liver conditions, heavy alcohol use, or poor nutrition are at higher risk because their livers have fewer protective reserves to begin with.
Dependence and Tolerance
As a Schedule III controlled substance, Tylenol 3 carries a moderate risk of physical dependence and a higher risk of psychological dependence. Codeine activates the same brain receptors as stronger opioids like oxycodone and morphine, just less potently. With regular use over days to weeks, your body adapts to the drug’s presence, and stopping abruptly can trigger withdrawal symptoms like restlessness, muscle aches, sweating, and insomnia. Tolerance also builds, meaning the same dose provides less relief over time, which can push people toward taking more than prescribed.
For these reasons, Tylenol 3 is typically prescribed for short-term pain management rather than chronic conditions. It occupies a middle ground in pain treatment: stronger than over-the-counter options, but weaker and considered lower-risk than Schedule II opioids like oxycodone or hydrocodone.