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Acetaminophen / Pentazocine Dosage

Applies to the following strengths: 650 mg-25 mg

Usual Adult Dose for Pain

Mild to moderate pain: 1 tablet orally every 4 hours as needed for pain relief
Maximum dose: 6 tablets/24 hours

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Data not available

Dose Adjustments

Due to the potential for withdrawal symptoms associated with abrupt discontinuation, patients should be tapered off acetaminophen-pentazocine following prolonged treatment with acetaminophen-pentazocine.


Cases of acute liver failure (some resulting in liver transplant and death) have been reported with acetaminophen. Most cases of liver injury are associated with doses greater than 4 g per day, and often involve more than one acetaminophen-containing product. The excessive intake of acetaminophen may be intentional to cause self-harm or unintentional as patients try to get more pain relief or unknowingly take other acetaminophen-containing products. Patients should be advised to check package labels for acetaminophen (or APAP) and not to use more than one product that contains acetaminophen. Patients should seek medical attention at once if more than 4 g of acetaminophen is taken per day, even if they feel well.

Acetaminophen-pentazocine should be used with caution in patients with hepatic impairment and in patients who ingest alcohol as the risk of acute liver failure is higher in such patients while taking acetaminophen.

Acetaminophen-pentazocine is contraindicated in patients with sulfite allergy.

Hypersensitivity and anaphylaxis have been reported during postmarketing experience with acetaminophen. Infrequently, life-threatening anaphylaxis requiring emergency medical attention has been reported. Acetaminophen-pentazocine should be stopped at once and patients should seek medical care if symptoms (e.g., swelling of the face, mouth, and throat, respiratory distress, urticaria, rash, pruritus, and vomiting) develop.

The possible respiratory depressant effects of pentazocine and its potential to elevate cerebrospinal fluid pressure may be markedly increased in the presence of head injury, intracranial lesions, or a preexisting increase in intracranial pressure. Extreme caution is recommended if pentazocine use is deemed essential in such patients.

Respiratory depression occurs more often in elderly or debilitated patients and in those suffering from conditions accompanied by hypoxia, hypercapnia, or upper airway obstruction. In such patients, even moderate therapeutic doses may decrease pulmonary ventilation significantly. Acetaminophen-pentazocine should be used with extreme caution in patients with chronic obstructive pulmonary disease or cor pulmonale and in patients with substantially decreased respiratory reserve (e.g., severe kyphoscoliosis), hypoxia, hypercapnia, or preexisting respiratory depression. Alternative non-opioid analgesics should be considered. Acetaminophen-pentazocine should be used only under careful medical supervision at the lowest effective dose in these patients.

Patients receiving therapeutic doses of acetaminophen-pentazocine have experienced hallucinations (usually visual), disorientation, and confusion which have cleared spontaneously within hours. Such patients should be closely observed and vital signs checked. If the drug is reinstituted, it should be done with caution since these acute central nervous system manifestations may recur.

Acetaminophen-pentazocine should be used with caution in patients prone to seizures.

Acetaminophen-pentazocine should be used with particular caution in patients with porphyria as it may cause an acute attack in susceptible patients.

Pentazocine can elevate blood pressure, possibly through endogenous catecholamine release. In conditions where changes in vascular resistance and blood pressure may be especially undesirable (e.g., acute phase of myocardial infarction), particular caution is recommended. Acetaminophen-pentazocine should be used with caution in patients with myocardial infarction who have nausea or vomiting.

Pentazocine has not been shown to cause or increase renal or hepatic impairment; however, it should be used with caution in patients with such impairment.

Acetaminophen-pentazocine should be used with caution in patients with hypothyroidism, adrenocortical insufficiency, prostate hypertrophy, inflammatory or obstructive bowel disease, acute abdominal syndromes of unknown etiology, cholecystitis, pancreatitis, or acute alcohol intoxication and delirium tremens.

Pentazocine can cause psychological and physical dependence. Some cases of dependence and of withdrawal symptoms have been reported with acetaminophen-pentazocine. Patients with a history of drug dependence should be supervised closely while using oral pentazocine.

Withdrawal symptoms (such as abdominal cramps, nausea, vomiting, elevated temperature, chills, rhinorrhea, restlessness, anxiety, or lacrimation) have occurred due to abrupt dose cessation or rapid dose reduction following extended use of parenteral pentazocine. In general, opioid therapy should not be abruptly discontinued. When acetaminophen-pentazocine therapy is no longer needed, the drug should be tapered gradually to prevent signs and symptoms of withdrawal in patients who have received opioids for an extended period and may be physically dependent.

When prescribing acetaminophen-pentazocine for chronic use, physicians should keep in mind that proper patient assessment, proper prescribing practices, periodic reevaluation of therapy, and proper dispensing and storage are appropriate measures that help to identify and decrease misuse and abuse of opioid drugs.

Misuse of tablets by injection (either alone or in combination with other substances) may result in severe, even lethal, consequences (e.g., pulmonary emboli, vascular occlusion, ulceration and abscesses, and withdrawal symptoms) in narcotic dependent patients.

Safety and efficacy have not been established in pediatric patients less than 12 years of age.


Data not available

Other Comments

The FDA has asked manufacturers to limit the maximum amount of acetaminophen in prescription products to 325 mg per dosage unit. There are no data that indicate that taking more than 325 mg of acetaminophen per dosage unit provides more pain relief. The goal of the FDA is to reduce the risk of severe liver injury from acetaminophen overdose, which can lead to liver failure, liver transplant, and even death. The total number of units that may be prescribed and the time intervals for dosing will not change. Drug companies will have until January 14, 2014 to comply with FDA requirements.

Usual acetaminophen maximum dosage is 4 g per day.

Pentazocine may impair the mental abilities necessary for potentially hazardous tasks such as driving or operating machinery.

As with other opioids, patients using acetaminophen-pentazocine should be advised of the potential for severe constipation. Appropriate laxatives and/or stool softeners plus other appropriate treatments should be started at the onset of opioid therapy.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.