Although acetaminophen relieves pain, it does not reduce inflammation. Acetaminophen causes few side effects and is used as a pain reliever for mild-to-moderate OA.

The usual recommended dose of acetaminophen regular-release tablets is 500 mg to 1,000 mg every 4 to 6 hours as needed, not to exceed a maximum of 4,000 mg per day. The usual recommended dose of acetaminophen extended-release tablets for arthritis pain is 1,300 mg every 8 hours, to a maximum daily dose of 4,000 mg.

Although acetaminophen has few side effects, it is possible to overdose by taking a large amount of acetaminophen in a single dose, which may result in potentially fatal liver toxicity. People most at risk for the effects of acetaminophen overdose are those who abuse alcohol and those with muscle wasting due to conditions such as cancer. Acetaminophen rarely produces liver damage at normal doses. There may be a link between long-term use of acetaminophen and kidney damage. If you are using acetaminophen regularly, your doctor may order periodic blood tests to check your kidney and liver function.

Many popular over-the-counter medications for colds and flu also contain acetaminophen. If you take acetaminophen regularly for pain relief from your OA, talk to your pharmacist before choosing a medication to treat any other condition. You might be getting too much acetaminophen without knowing it.

Very few medications interact with acetaminophen. Acetaminophen taken in doses of 2,000 mg (2 g) daily or higher may cause you to bleed more easily if you take anticoagulant medications as well, such as warfarin. If you are taking 2,000 mg or more of acetaminophen on a regular basis in combination with warfarin, your doctor may check your blood clotting time (international normalized ratio or INR) more frequently.

Narcotic pain relievers

Your doctor may recommend narcotic pain relievers, often combined with acetaminophen, if your OA pain is severe and other medications aren't working, or if you can't take NSAIDs. Narcotic pain relievers may reduce pain effectively but they do not reduce inflammation. Narcotic pain relievers include medications such as codeine, oxycodone, morphine, oxymorphone, tramadol, and fentanyl.

Narcotic pain relievers may cause addiction, and some people may abuse them. Side effects include constipation, drowsiness, nausea, vomiting, confusion, and urine retention.

If you take medications that already cause drowsiness, such as antianxiety medications (e.g., clonazepam, lorazepam and others), you should make sure that your doctor is aware that you take them.