Analgesic and Side Effects of Pentazocine and Morphine in a Large Population of Postoperative Patients

Abstract

The analgesic and side effects of pentazocine were compared with those of morphine in 1,074 surgical patients. Three separate three-point assays were conducted. Standard doses used were 5 mg. and 10 mg. of morphine and 10 mg., 20 mg., and 40 mg. of pentazocine. The relative analgesic potency, based on a 225 minute time period for analgesic effect, was 0.28 (36 mg. of pentazocine ~ 10 mg. of morphine). For peak pain intensity difference, the relative potency was found to be 0.38 (27 mg. of pentazocine ~ 10 mg. of morphine).

Pentazocine

“…It is doserelated (Hamilton et al, 1967b) and appears to vary considerably between hospitals. Paddock et al (1969) reported an incidence varying between 12.8 and 80 % from 5 hospitals all following the same study protocol. When pooled, these results indicated that 40 mg had a higher incidence of sedation than 10 mg morphine.…”

“…In view of the findings of Paddock et al (1969), which showed that 36 mg pentazocine is approximately equivalent to 10 mg morphine in total analgesic effect, pentazocine given in approximately equianalgesic single dosages produces a comparable degree of sedation, dizziness and respiratory depression and a similar incidence of nausea, vomiting, sweating, and other minor subjective complaints as do the narcotic analgesics. However, constipation and urinary retention, biliary tract spasm and gastro-intestinal upset may not be such significant problems with pentazocine.…”

“…In a study involving 1,074 surgical patients, Paddock et al (1969) compared the effects of intramuscular pentazocine 10 mg, 20 mg and 40 mg with those of intramuscular morphine sulphate 5 mg and 10 mg, on both the intensity of pain and on its duration. They showed that 27 mg of pentazocine provided about the same pain relief as 10 mg of morphine when peak effects were compared, but when the analgesic potency was assessed over a period of about 4 hours 36 mg of pentazocine was required to equal the effect of morphine 10 mg, indicating that the effect of pentazocine declines more rapidly than that of morphine.…”

“…Side-effects of pentazocine are discussed in section 6. Paddock et al (1969) reported a difference between the time-effect curves for pentazocine and morphine. Pentazocine had a higher initial peak of analgesic activity than morphine, but its effect declined more rapidly.…”

“…Hamilton et al, 1967b) than in those in which patients were immobilised by moderate to severe pain (e.g. Paddock et al, 1969). Other gastro-intestinal effects reported infrequently or rarely include constipation, taste alteration , diarrhoea, cramps and dyspepsia.…”