Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2019 Publisher: Generics [UK] Limited t/a Mylan, Station Close, Potters Bar, Hertfordshire, EN6 1TL, United Kingdom
Pentazocine can both depress as well as elevate blood pressure possibly through the release of endogenous catecholamines. Particular caution should be observed therefore in using it in the presence of phaeochromocytoma, in the acute phase following myocardial infarction when it may increase pulmonary and systemic arterial pressure and vascular resistance, and in other clinical situations where alteration of vascular resistance and blood pressure might be particularly undesirable.
Caution should be exercised when administering high doses of pentazocine to patients who have suffered a recent myocardial infarction due to increases in heart rate and blood pressure.
Pentazocine should be given with caution to patients with severely imparired renal or hepatic function and in elderly patients, who may additionally be especially sensitive to the effects of opioids, as both conditions may lead to an increase in bioavailability of pentazocine and call for a reduction in dosage.
Administer with caution to patients previously on large doses of narcotics.
Cautions should be observed in patients who are prone to seizures.
Patients taking other opioids should be treated cautiously and pentazocine should not be used on patients already dependent on other opioids since the weak opioid antagonistic effects of pentazocine may provoke withdrawal symptoms.
Caution should also be observed in patients with hypothyroidism, adrenocortical insufficiency, prostatic hypertrophy and in patients with inflammatory or obstructive bowel disorders, cholecystitis, pancreatitis or other unidentified abdominal pain.
When pentazocine is prescribed for chronic use, the physician should take precautions to avoid any unnecessary increase in dose by the patient since prolonged use of high doses of pentazocine may produce a dependence. Patients with a history of drug abuse should be closely supervised when receiving pentazocine.
Concomitant use of Pentazocine and sedative medicines such as benzodiazepines or related drugs may result in sedation, respiratory depression coma and death. Because of these risks, concomitant prescribing with these sedative medicines should be reserved for patients for whom alternative treatment options are not possible. If a decision is made to prescribe Pentazocine concomitantly with sedative medicines, the lowest effective dose should be used, and the duration of treatment should be as short as possible.
The patients should be followed closely for signs and symptoms of respiratory depression and sedation. In this respect, it is strongly recommended to inform patients and their caregivers to be aware of these symptoms (see section 4.5).
Some opioids can cause CNS excitation or depression.
Pentazocine, like most other strong analgesics, should not be used in patients who are receiving monoamine oxidase inhibitors or who have received them within the past 14 days. (see section 4.5) Opioids can be taken after two weeks of MAOI’s discontinuation
After long term treatment (> 3 months) of analgesics with use every second day or more frequently, headache may develop or aggravate. Headache caused by overuse of analgesics (MOH – medication-overuse headache) should not be treated by increasing the dose. In such cases the use of analgesics should be discontinued in consultation with a doctor.
There have been rare reports of mild withdrawal symptoms in the new-born after prolonged maternal use of pentazocine during pregnancy. This abstinence syndrome of pentazocine is not typical of opiate dependence. Symptoms include mild abdominal cramps, nausea, vomiting, nervousness or estlessness, dizziness, fever and chills, but are mild compared with opiate withdrawal symptoms. Withdrawal of pentazocine from such patients has caused few problems only occasionally requiring treatment with tranquillisers. It should be emphasised that the majority of patients reported to have become dependant on pentazocine had previously been dependant on opiates or had misused other drugs.
Monoamine oxidase inhibitors may enhance the opioid effects of pentazocine and the agents may interact through their respective effects on catecholamine breakdown and release.
Pentazocine, should not be used in patients who are receiving monoamine oxidase inhibitors or who have received them within the past 14 days (see section 4.4).
Agents with sedative action including phenothiazines, tricyclic antidepressants and ethyl alcohol can enhance the central depressant effects of pentazocine which are opposed by respiratory stimulants such as doxapram.
Tobacco smoking appears to enhance the metabolic clearance rate of pentazocine reducing the clinical effectiveness of a standard dose of pentazocine.
Pentazocine can antagonise the effects of stronger opioid agonists such as diamorphine (heroin) and morphine, and may provoke withdrawal symptoms if given to narcotic addicts. It is itself antagonised by naloxone.
Sedative medicines such as benzodiazepines or related drugs: The concomitant use of opioids with sedative medicines such as benzodiazepines or related drugs increases the risk of sedation, respiratory depression, coma and death because of additive CNS depressant effect. The dose and duration of concomitant use should be limited (see section 4.4).
There is no epidemiological evidence for the safety of pentazocine in human pregnancy, but it has been widely used for many years without apparent ill consequences. Doses which produce maternal toxicity in rats have caused harmful effects in the foetus. Pentazocine can rapidly cross the placental barrier and enter the foetal circulation and has the potential to cause opioid effects including central depression and abstinence syndrome in the foetus and newborn infant. It does not appear to have significant adverse effects on uterine function at parturition. Nonetheless, careful consideration should be given to the use of pentazocine during pregnancy, particularly during the first trimester, or at term. Special attention should be paid to clinical monitoring of the newborn, particularly premature infants, if pentazocine has been used during labour.
Pentazocine is excreted in very small amounts in breast milk. Caution should therefore be observed in administering pentazocine to breast-feeding mothers, particularly of infants at risk.
It is recommended that infants of nursing mothers who are receiving high doses of pentazocine, be appropriately monitored.
As Pentazocine may produce sedation, dizziness and occasionally euphoria, so ambulant patients should be warned against the performance of potentially hazardous tasks such as driving a car or not operating machinery. Alcohol may potentiate the sedative effect.
This medicine can impair cognitive function and can affect a patient’s ability to drive safely. This class of medicine is in the list of drugs included in regulations under 5a of the Road Traffic Act 1988. When prescribing this medicine, patients should be told:
In chronic usage, care should be exercised to avoid any unnecessary increase in dosage since prolonged use of high dosage of pentazocine may produce dependence.
At normal therapeutic doses, side-effects are generally of a minor nature. Sedation and drowsiness, the most common effect, is less than that associated with morphine. The most frequent side effects are light-headedness, dizziness, sedation, nausea, vomiting and sweating.
Blood and lymphatic system disorders: transient eosinophilia, agranulocytosis, depression of white blood cells.
Immune system disorders: oedema of the face, flushing of the skin, including facial plethora, skin rashes, urticaria, dermatitis including pruritus, chills and allergic reactions.
Nervous system disorders: hallucinations may occur occasionally, dysphoria, disturbances of visison, headache, disorientation, mood changes, nightmares, insomnia, paraesthesia, syncope, euphoria, grand mal convulsions, raised intracranial pressure, confusion, muscle tremor, thought disturbances.
Eye disorders: miosis, disturbances of vision.
Cardiac disorders: transient hypertension, tachycardia, bradycardia, hypotension, circulatory depression, palpitations.
Respiratory, thoracic and mediastinal disorders: respiratory depression.
Gastrointestinal disorders: dry mouth, constipation, ureteric or biliary spasm, abdominal pain.
Skin and subcutaneous system disorders: toxic epidermal necrolysis.
Renal and urinary disorders: urinary retention, ureteric tract spasm.
Pregnancy, puerperium and perinatal conditions: alterations in rate or strength of uterine contractions during labour.
Reproductive system and breast disorders: decreased libido or potency.
General disorders and administration site conditions: hypothermia.
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.
Not applicable.
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