Classifications: narcotic (opiate) agonist-antagonist; analgesic;
Therapeutic: narcotic
; analgesic
Pregnancy Category: C
Controlled Substance: Schedule IV


30 mg/mL injection


Synthetic analgesic with analgesic potency approximately one-third that of morphine. Opiates exert their analgesic effects by stimulating specific opiate receptors that produce analgesia, respiratory depression, and euphoria as well as physical dependence.

Therapeutic Effect

Effective for moderate to severe pain relief. Acts as weak narcotic antagonist and has sedative properties.


Relief of moderate to severe pain; also used for preoperative analgesia or sedation, and as supplement to surgical anesthesia.


Hypersensitivity to sulfite; head injury, increased intracranial pressure; seizures; emotionally unstable patients, or history of drug abuse; pregnancy (other than labor) (category C), lactation. Safe use in children <12 y is not established.

Cautious Use

Impaired kidney or liver function; cardiac disease; COPD, asthmas, respiratory depression; GI obstruction; biliary surgery; patients with MI who have nausea and vomiting.

Route & Dosage

Moderate to Severe Pain (Excluding Patients in Labor)
Adult: IM/IV/SC 30–60 mg q3–4h (max: 360 mg/d)
Child: IM 15–30 mg

Women in Labor
Adult: IM 20–30 mg; 20 mg may be repeated 1 or 2 times at 2–3 h intervals

Renal Impairment
Clcr 10–50 mL/min: give 75% of dose; <10 mL/min: give 50% of dose


  • IM is preferred to SC route when frequent injections over an extended period are required.
  • Observe injection sites daily for signs of irritation or inflammation.

PREPARE: Direct: Give undiluted or diluted with 1 mL sterile water for injection for each 5 mg.  

ADMINISTER: Direct: Give slowly at a rate of 5 mg over 60 sec.  

INCOMPATIBILITIES Solution/additive: Aminophylline, barbiturates, sodium bicarbonate, glycopyrrolate, heparin, nafcillin. Y-site: Nafcillin.

Adverse Effects (≥1%)

Body as a Whole: Flushing, allergic reactions, shock. CNS: Drowsiness, sweating, dizziness, light-headedness, euphoria, psychotomimetic effects, confusion, anxiety, hallucinations, disturbed dreams, bizarre thoughts, euphoria and other mood alterations. CV: Hypertension, palpitation, tachycardia. GI: Nausea, vomiting, constipation, dry mouth, alterations of taste. Urogenital: Urinary retention. Respiratory: Respiratory depression. Skin: Injection-site reactions (induration, nodule formation, sloughing, sclerosis, cutaneous depression), rash, pruritus. Special Senses: Visual disturbances.


Drug: Alcohol and other cns depressants add to CNS depression; narcotic analgesics may precipitate narcotic withdrawal syndrome.


Onset: 15 min IM, SC; 2–3 min IV. Peak: 1 h IM, 15 min IV. Duration: 3 h IM, 1 h IV. Distribution: Crosses placenta. Metabolism: Extensively in liver. Elimination: Primarily in urine; small amount in feces. Half-Life: 2–3 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor therapeutic effect. Tolerance to analgesic effect sometimes occurs. Psychologic and physical dependence have been reported in patients with history of drug abuse, but rarely in patients without such history. Addiction liability matches that of codeine.
  • Monitor vital signs and assess for respiratory depression. Keep supine to minimize adverse efffects.
  • Monitor drug-induced CNS depression.
  • Be aware that pentazocine may produce acute withdrawal symptoms in some patients who have been receiving opioids on a regular basis.
  • Monitor I&O as drug may cause urinary retention.

Patient & Family Education

  • Avoid driving and other potentially hazardous activities until response to drug is known.
  • Do not discontinue drug abruptly following extended use; may result in chills, abdominal and muscle cramps, yawning, runny nose, tearing, itching, restlessness, anxiety, drug-seeking behavior.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2022 Last Updated On: 12/03/2022 (0)
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