Cardiovascular: Hypotension, tachycardia, syncope.
Respiratory: Rarely, respiratory depression.
Acute CNS Manifestations: Patients receiving therapeutic doses of pentazocine have experienced hallucinations (usually visual), disorientation, and confusion which have cleared spontaneously within a period of hours. The mechanism of this reaction is not known. Such patients should be closely observed and vital signs checked. If the drug is reinstituted it should be done with caution since these acute CNS manifestations may recur.
Other CNS Effects: Dizziness, lightheadedness, hallucinations, sedation, euphoria, headache, confusion, disorientation; infrequently weakness, disturbed dreams, insomnia, syncope, visual blurring and focusing difficulty, depression; and rarely tremor, irritability, excitement, tinnitus.
Autonomic: Sweating; infrequently flushing; and rarely chills.
Gastrointestinal: Nausea, vomiting, constipation, diarrhea, anorexia, rarely abdominal distress.
Allergic: Edema of the face; dermatitis, including pruritus; flushed skin, including plethora; infrequently rash, and rarely urticaria.
Ophthalmic: Visual blurring and focusing difficulty.
Hematologic: Depression of white blood cells (especially granulocytes), which is usually reversible, moderate transient eosinophilia.
Other: Headache, chills, insomnia, weakness, urinary retention, paresthesia, serious skin reactions, including erythema multiforme, Stevens-Johnson Syndrome and toxic epidermal necrolysis.