PMID: 6109016Oct 1, 1980Paper

Comparative cardiac contractile actions of six narcotic analgesics: morphine, meperidine, pentazocine, fentanyl, methadone and l-alpha-acetylmethadol (LAAM)

The Journal of Pharmacology and Experimental Therapeutics
S V RendigD T Mason

Abstract

Cardiac muscle contractile responses to six narcotic analgesics (morphine, meperidine, pentazocine, fentanyl, methadone and l-alpha-acetylmethadol), at concentrations from 10(-8) to 10(-4) M, both in the presence and absence of the narcotic antagonist, naloxone, were studied in the isolated, isometric cat right ventricular papillary muscle preparation. Measurements of maximum developed tension (T), maximum rate of tension development (dT/dt) and time to peak tension indicated that no major changes in contractile function occurred with any narcotic at concentrations of 10(-8) to 10(-6) M except for small but significant (P < .05) increases in all three parameters at 10(-6) M fentanyl, and small but significant increases in dT/dt at 10(-8) to 10(-6) M meperidine. At 10(-5) M narcotic, dT/dt was significantly elevated in meperidine-treated muscles (+7%), but significantly reduced in muscles exposed to pentazocine (-8%) or l-alpha-acetylmethadol (-11%). For all six narcotics, the 10(-4) M drug concentration resulted in depression of contractile function that was often associated with nonresponsiveness to electrical stimulation. Pretreatment of muscles with naloxone (10(-4) M) did not prevent this reduction of contractile performanc...Continue Reading

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