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naloxone/pentazocine (Talwin NX)
50 mg pentazocine + 0.5 mg naloxone. DEA-controlled substance: class 4.
Indications:
1) treatment of mild to moderate acute pain-related syndromes
2) treatment of some chronic pain syndrome
Contraindications:
- increase intracranial pressure (unless patient is mechanically ventilated)
Caution:
- NOT recommended for patients with seizures or psychosis
Dosage:
1) 1 tab PO every 3-4 hours or every 4-6 hours; max: 12 tabs/day
2) 1 tab every 6-8 hours with hepatic dysfunction; max: 8 tabs/day
Pharmacokinetics:
1) well absorbed orally
2) only 20% reaches circulation unchanged due to 1st pass metabolism
3) bioavailability is increased in patients with hepatic dysfunction
4) onset of analgesia is 15-30 minutes
5) duration of action is 3-4 hours
6) metabolized in liver
6) elimination 1/2life is 2-3 hours, prolonged with hepatic dysfunction
Adverse effects:
1) common (> 10%)
- euphoria, nausea/vomiting, weakness, drowsiness
2) less common (1-10%)
- malaise, headache, hypotension, restlessness, nightmares, ureteral spasm, dry mouth, blurred vision, rash, dyspnea
3) uncommon (< 1%)
- GI irritation, insomnia, palpitations, bradycardia, peripheral vasodilation, CNS depression, sedation, hallucinations, confusion, disorientation, seizures may occur in seizure-prone patients, pruritus, antidiuretic hormone release, constipation, tissue injury with IM & SC administration, miosis, biliary spasm, histamine release, increased intracranial pressure, physical & psychologic dependence
4) other [2]
a) respiratory depression
b) constipation (generally mild)
c) withdrawal in opiate-dependent patients
5) overdose:
a) airway support
b) IV administration of naloxone
1] 2 mg (0.01 mg/kg in children)
2] may repeat up to a total of 10 mg
Drug interactions:
1) opioid agonists: mu receptor antagonism may precipitate withdrawal
2) naloxone is a direct opioid antagonist
3) fluoxetine in combination may cause serotonin syndrome
4) MAO inhibitors in combination may result in hypertensive crisis
5) additive effects with other CNS depressants
a) phenothiazines
b) sedatives
c) anxiolytics
d) hypnotics
e) alcohol
6) tripepennamine potentiates pentazocine effects & toxicity
Mechanism of action:
1) opioid partial agonist
a) competitive antagonist at opioid mu receptors
b) agonist at opioid kappa & sigma receptors
c) will stimulate withdrawal in physically-dependent patients
2) naloxone
a) given orally has no effect on activity of pentazocine
b) if ground & given parenterally, naloxone will antagonize effects of pentozocine
c) added to prevent abuse by injecting ground & dissolved tablets
General
pharmacologic combination
References
- The Pharmacological Basis of Therapeutics, 9th ed.
Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- Drug Information & Medication Formulary, Veterans Affairs,
Central California Health Care System, 1st ed., Ravnan et al
eds, 1998 - not on National VA formulary
- Kaiser Permanente Northern California Regional Drug
Formulary, 1998
Components
naloxone (Narcan, Evzio, ReVive)
pentazocine (Talwin)