propoxyphene and acetaminophen (Darvocet)

Propoxyphene and acetaminophen is indicated for the relief of mild to moderate pain. It can also reduce fever.

Propoxyphene is a strong narcotic pain-reliever and cough suppressant but is weaker than other narcotics such as morphine, codeine, and hydrocodone. The precise mechanism of action is not known but may involve stimulation of opioid receptors in the brain. Propoxyphene increases pain tolerance and decreases discomfort, but the presence of pain is still apparent. In addition to pain reduction, propoxyphene also causes sedation and respiratory depression. Acetaminophen is a non-narcotic analgesic and antipyretic (fever reducer). Acetaminophen relieves pain by elevating the pain threshold. It reduces fever through its action on the heat-regulating center of the brain. The combination of propoxyphene and acetaminophen achieves greater pain relief than either taken separately. For more information on acetaminophen, please see acetaminophen (Tylenol). The FDA first approved propoxyphene/acetaminophen combinations in October 1972.

Is propoxyphene and acetaminophen available as a generic drug?

Yes

Do I need a prescription for propoxyphene and acetaminophen?

Yes

The most frequent adverse reactions of propoxyphene include:

• lightheadedness,
• dizziness,
• sedation,
• nausea, and
• vomiting.

Other side effects include:

• drowsiness,
• constipation, and
• spasm of the ureter, which can lead to difficulty in urinating.

Propoxyphene can depress breathing and, therefore, is used with caution in elderly, debilitated patients, and in patients with serious lung disease. Propoxyphene can impair thinking and the physical abilities required for driving or operating machinery. Propoxyphene may be habit forming. Mental and physical dependence can occur but are unlikely when it is used short-term.

The recommended adult dose is 1-2 tablets every 4 hours as needed for relief of pain. The total dose should not exceed six 100/650 mg tablets or twelve 50/325 mg tablets in a 24-hour period.

Propoxyphene, like other narcotic pain-relievers, increases the effect of drugs that slow brain function, such as alcohol, barbiturates, skeletal muscle relaxants, for example, carisoprodol (Soma) and cyclobenzaprine (Flexeril), and benzodiazepine sedatives, for example, diazepam (Valium) and lorazepam (Ativan). Combined use of muscle relaxants and propoxyphene may lead to greater respiratory depression than either drug alone.

Combining propoxyphene with carbamazepine (Tegretol, Tegretol XR , Equetro, Carbatrol) may have severe effects on the brain including coma. Since propoxyphene causes constipation, the use of antidiarrheals, for example, diphenoxylate (Lomotil) and loperamide (Imodium), in persons taking propoxyphene can lead to severe constipation.

Drugs which both stimulate and block opioid receptors for example pentazocine (Talwin), nalbuphine (Nubain), butorphanol (Stadol), and buprenorphine (Buprenex), may reduce the effect of propoxyphene or may precipitate withdrawal symptoms from propoxyphene. Acetaminophen is metabolized (eliminated by conversion to other chemicals) by the liver. Therefore drugs that increase the action of liver enzymes that metabolize acetaminophen, for example, carbamazepine (Tegretol), isoniazid (INH, Nydrazid, Laniazid), and rifampin (Rifamate, Rifadin, Rimactane), reduce the levels of acetaminophen and therefore may decrease its action. Doses of acetaminophen greater than the recommended doses are toxic to the liver and may result in severe liver damage. The potential for acetaminophen to harm the liver is increased when it is combined with alcohol or drugs that also harm the liver.

Cholestyramine (Questran) reduces the effect of acetaminophen by decreasing its absorption into the body from the intestine. Therefore, acetaminophen should be administered 3 to 4 hours after cholestyramine or one hour before cholestyramine. Acetaminophen doses greater than 2275 mg per day may increase the blood thinning effect of warfarin (Coumadin) by an unknown mechanism. Therefore, prolonged administration or large doses of acetaminophen should be avoided during warfarin therapy.

Low concentrations of propoxyphene have been measured in the breast milk of mothers taking propoxyphene. It is not known whether these small amounts can cause side effects in nursing infants.

What preparations of propoxyphene and acetaminophen are available?

Tablets: propoxyphene/acetaminophen 50/325, 65/650, 100/325, 100/500, and 100 mg/650 mg

How should I keep propoxyphene and acetaminophen stored?

Tablets should be stored at room temperature, 15 C to 30 C (59 F to 86 F).