Pentazocine

Pentazocine is indicated for the relief of moderate to severe pain. It may also be used for preoperative or preanesthetic medication and as a supplement to surgical anesthesia.

Pentazocine is an opioid (narcotic) analgesic. It works in the brain and nervous system to decrease pain. It produces analgesia by an agonistic effect at the kappa receptor. It weakly antagonizes effects of opiates at μ-receptor.

Onset: IM/subcutaneous is 15 to 20 min; IV is 2 to 3 min.
Distribution: Moderate protein binding.
Metabolism: Hepatic.
Elimination: Excreted primarily by the kidney. Half-life is 2 to 3 h.

Usual Adult Dose for Anesthesia & Moderate to severe pain: 30 mg by IV, IM or SC. This may be repeated every 3 to 4 hours. Doses in excess of 30 mg intravenously or 60 mg intramuscularly or subcutaneously are not recommended. Maximum daily dose: 360 mg

Usual Adult Dose for Labor Pain: 30 mg intramuscularly once has been the most common dose administered. An intravenous 20 mg dose has given adequate pain relief to some patients in labor when contractions become regular. This dose may be given two or three times at two or three hour intervals as needed.

Dose for Children >1 year old: 0.5 mg/kg by intramuscular injection.

Drinking of alcohol should be avoided. Dangerous side effects or death can occur when alcohol is combined with pentazocine. Using this medicine with other drugs that make sleepy or slow breathing can worsen these effects. Dizziness or severe drowsiness can cause falls or other accidents. Other drugs may interact with pentazocine, including prescription and over-the-counter medicines, vitamins, and herbal products.

Pentazocine should not be administered to patients who are hypersensitive to it.

The most commonly occurring reactions are: nausea, dizziness or light-headedness, vomiting, euphoria. Several dermatologic, respiratory, cardiovascular, gastrointestinal side effects may also happen.

Pregnancy category C. Pentazocine should be given during pregnancy when need has been clearly established. There are no data on the excretion of pentazocine into human milk.

Pentazocine should be administered only with caution and in low dosage to patients with respiratory depression. Although laboratory tests have not indicated that Pentazocine causes or increases renal or hepatic impairment, the drug should be administered with caution to patients with such impairment. Pentazocine is a mild narcotic antagonist. Some patients previously given narcotics, including methadone for the daily treatment of narcotic dependence, have experienced withdrawal symptoms after receiving Pentazocine. Caution should be used when Pentazocine is administered to patients prone to seizures; seizures have occurred in a few such patients in association with the use of Pentazocine. Concomitant use of CNS depressants with parenteral Pentazocine may produce additive CNS depression.

Manifestations: Clinical experience with Pentazocine overdosage has been insufficient to define the signs of this condition.

Treatment: Oxygen, intravenous fluids, vasopressors, and other supportive measures should be employed as indicated. Assisted or controlled ventilation should also be considered. For respiratory depression due to overdose or unusual sensitivity to Pentazocine, parenteral naloxone is a specific and effective antagonist.

Opioid analgesics

Keep away from light and store below 25°C. Do not freeze. Keep out of reach of children.