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July 27, 1964

Pentazocine vs Morphine

JAMA. 1964;189(4):332. doi:10.1001/jama.1964.03070040082033

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To the Editor:—  Our conclusions are based upon clinical evaluation of these analgesics. We are well aware, as indicated in our communication, that 40 mg of pentazocine is not equal to 20 mg of morphine sulfate. To extrapolate data, without clinical evidence, and conclude that 90 mg of pentazocine is approximately equal to 20 mg of morphine sulfate may be a satisfactory technique from a purely theoretical point, but could not be of immediate clinical use.To establish the equivalent potency of pentazocine and morphine requires dosages of pentazocine which surpass the analgesic effect of morphine, as well as dosages which provide less pain relief than morphine. Interpolation of the data is now possible. We are, however, extremely reluctant to use extrapolation techniques, especially in view of the nonlinearity of the pain scale. It was unfortunate that we did not include in our study a dosage regimen of 10 mg

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