Action And Clinical Pharmacology: Pentazocine is a member of the benzazocine series of synthetic benzomorphans. It produces both analgesic (agonist) and narcotic antagonist effects. The analgesic effect of 50 mg pentazocine administered orally is approximately equivalent to 60 mg codeine. Pentazocine also produces a sedative effect.
The onset of analgesia following oral administration of pentazocine can occur within 15 to 30 minutes and the duration of effect is usually 3 hours or longer. The onset and duration of analgesia are, in part, related to the dose and severity of pretreatment pain. Peak serum levels of pentazocine occur between 1 and 3 hours after oral administration. Approximately 60% of an oral dose is eliminated in the urine within 24 hours. There is considerable variability between individuals in terms of the rate of pentazocine metobolism which may also account for the variability in analgesic response.
Indications And Clinical Uses: For the relief of chronic or acute pain of moderate to severe degree.
Contra-Indications: Pentazocine should not be administered to patients with known hypersensitivity to pentazocine.
Pregnancy: The use of pentazocine in women of childbearing potential requires that the expected benefit of the drug be weighed against the potential risk to the mother and fetus.
Children: Clinical experience in children under 12 years of age is limited, therefore, use of pentazocine is not recommended in this age group.
Manufacturers’ Warnings In Clinical States: Drug Dependence: There have been reported instances of psychological and physical dependence upon parenteral pentazocine. These reports have primarily concerned patients with a previous history of drug abuse, although there have been instances reported in patients without such a history. Usually there was a description of an increase in the dose and frequency of administration by the patient. In these patients abrupt discontinuance of the drug often resulted in withdrawal symptoms including abdominal cramps, elevated temperatures, rhinorrhoea, restlessness, anxiety and lacrimation. There have been reports of dependence upon oral pentazocine. Consequently, patients who may be prone to excessive usage of drugs should be supervised carefully during oral pentazocine therapy. During chronic use of pentazocine, the physician should avoid unnecessary escalation of the dose and should take precautions to avoid increases in dose by the patient. Physicians should warn the patient against the use of pentazocine in anticipation of pain.
Head Injury and Increased Intracranial Pressure: The respiratory depressant effects of pentazocine and its potential for elevating cerebrospinal fluid pressure may be markedly exaggerated in the presence of head injury, other intracranial lesions or a pre-existing increase in intracranial pressure. Pentazocine can produce effects which may obscure the clinical course of patients with head injuries. Pentazocine must be used with caution in such patients, and only if its use is deemed essential.
Acute CNS Manifestations: There have been reported instances of the acute onset of hallucinations (usually visual), disorientation, and confusion in patients receiving therapeutic doses. These manifestations have cleared spontaneously within hours upon discontinuation of the drug. The mechanism responsible for this reaction is not known. Patients demonstrating this reaction should be closely observed and if therapy with pentazocine is to be restarted, administration should proceed cautiously since the acute CNS manifestations may recur.
Precautions: Occupational Hazards: Since CNS effects have been noted with the use of pentazocine ambulatory patients should be warned not to operate machinery, drive cars or unnecessarily expose themselves to hazards.
Patients Dependent on Narcotics: Because pentazocine is a weak narcotic antagonist, patients who are addicted to narcotics may experience withdrawal symptoms and therefore it should be given with special caution to such persons. In non-addicted patients receiving narcotics for a short period, symptoms believed to be related to antagonism may be observed. Intolerance or untoward reactions are usually not observed following administration of pentazocine to patients who have received single doses of, or who have had limited exposure to narcotics.
Impaired Renal or Hepatic Function: 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. Extensive liver disease appears to predispose to a higher incidence of side effects (e.g., marked apprehension, anxiety, dizziness, sleepiness) with the usual clinical dose, and may be the result of decreased metabolism of the drug by the liver.
Sphincter of Oddi: Until further experience is gained with the effects of pentazocine on the sphincter of Oddi, the drug should be used with caution in patients with acute cholecystitis or pancreatitis or in those about to undergo surgery of the biliary tract.
Obstructive Uropathy: Because urinary retention has been observed in a few patients receiving pentazocine, caution is advised in administration of the drug to patients with obstructive uropathy.
Respiratory Conditions: Respiratory depression has rarely been reported after oral administration, however, pentazocine, should be administered cautiously to patients with respiratory depression due to any cause, severely limited respiratory reserve, severe bronchial asthma, other obstructive respiratory conditions or cyanosis.
Myocardial Infarction: As with all drugs, pentazocine should be used with caution in patients with myocardial infarction who have nausea or vomiting.
Adverse Reactions: The most frequently observed reactions after oral administration of pentazocine are sedation or somnolence, vertigo, nausea and vomiting, each of which may occur in approximately 15% of patients. Sedation may be more marked in the elderly.
Less frequent reactions have been: Gastrointestinal: constipation, abdominal distress, anorexia and diarrhea.
CNS: euphoria, lightheadedness, headache, dizziness, weakness, disturbed dreams, hallucinations (see Acute CNS effects in Warnings), visual disturbances, insomnia, tinnitus, irritability, excitement.
Autonomic: sweating, infrequently flushing or chills.
Cardiovascular: infrequently fall in blood pressure, tachycardia.
Allergic: infrequently rash and rarely urticaria, erythema and edema.
Hematologic: rarely depression of white blood cells (especially granulocytes), which is usually reversible, moderate transient eosinophilia.
Other: pruritus, alterations in maturation. Scattered reports of abnormal liver function of questionable significance were noted during the clinical trials. Hallucinations were noted to occur more frequently when doses exceeding that recommended were employed.
Symptoms And Treatment Of Overdose: Symptoms and Treatment: The clinical picture of overdose has not been well defined but high doses will cause respiratory depression, increased blood pressure and tachycardia.
Should depression of respiration occur, oxygen, i.v. fluids, vasopressors, and other supportive measures should be employed as indicated. Assisted or controlled ventilation should also be considered. Although nalorphine and levallorphan are not effective antidotes for respiratory depression due to overdosage, parenteral naloxone is a specific and effective antagonist.
The recommended adult dose of naloxone is 0.4 mg (1 mL) administered i.v., i.m. or s.c. If the desired degree of counteraction and improvement in respiratory function is not obtained immediately, naloxone may be repeated at 2 to 3 minute intervals. Failure to obtain significant improvement after 2 to 3 doses suggests that causes other than pentazocine overdose may be responsible for the patient’s condition.
Dosage And Administration: Adults: Usual starting dose is 50 mg every 4 hours after meals. Dosage should be adjusted to individual requirements and tolerance within the range of 50 to 100 mg every 3 to 4 hours.
Concomitant Medication: When anti-inflammatory or antipyretic effects are desired in addition to analgesia, ASA can be administered concomitantly with pentazocine.
In light of the tendency to marked sedation among the elderly, dosage should be kept low in this group of patients.
Duration of Therapy: There have been rare reports of withdrawal symptoms upon abrupt discontinuance of therapy after prolonged administration of the product for chronic pain. Therefore, it would be prudent to reduce the dose gradually when the drug is no longer required.
Availability And Storage: Each scored peach tablet with a stylized “W” on one side and scored on the other with “T” above and “21” below the score, contains: pentazocine HCl equivalent to 50 mg base. Nonmedicinal ingredients: calcium phosphate (dibasic), colloidal silicon dioxide, FD and C Yellow lake #6, magnesium stearate, microcrystalline cellulose, sodium lauryl sulfate, sodium metabisulfite and starch. Gluten-, lactose- and tartrazine-free. Bottles of 100 and 500.
TALWIN® Tablets Sanofi Pentazocine HCl Analgesic