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Interactions between verapamil and morphine on physiological parameters in rats
Abstract:
Effects of s.c. doses of morphine and verapamil, alone and in combination, on arterial blood gases and pH, mean blood pressure and heart rate were assessed in partially restrained, awake Fischer-344 rats. As expected, morphine (4-16 mg/kg) produced a dose-dependent respiratory depression, as indicated by hypoxia, hypercapnia and acidosis. Verapamil, a calcium channel antagonist, alone (10 mg/kg) did not affect these parameters; however, it significantly attenuated and delayed the aforementioned effects of morphine. Morphine caused a slight increase in mean blood pressure, which was not dose dependent, whereas verapamil reduced blood pressure dramatically even in the presence of morphine. All groups showed some tachycardia, but rats treated with morphine alone showed the most pronounced increase in heart rate, which was antagonized by verapamil. The authors conclude that the interaction of verapamil with morphine's respiratory depressant effects differs from the previously reported potentiation of morphine's antinociceptive and hypothermic actions.
Insights
Verapamil, a calcium channel blocker, lessened morphine
Area of Science:
- Pharmacology
- Cardiovascular Physiology
- Respiratory Physiology
Background:
- Morphine is a potent opioid analgesic with known respiratory depressant effects.
- Verapamil is a calcium channel antagonist with cardiovascular effects.
- Interactions between opioids and calcium channel blockers require further investigation.
Purpose of the Study:
- To investigate the combined effects of morphine and verapamil on respiratory and cardiovascular parameters in rats.
- To determine if verapamil modulates morphine-induced respiratory depression.
- To assess the impact of verapamil on morphine's cardiovascular effects.
Main Methods:
- Fischer-344 rats were administered subcutaneous doses of morphine and verapamil, alone and in combination.
- Arterial blood gases, pH, mean blood pressure, and heart rate were monitored.
- Dose-dependent effects of morphine and verapamil were assessed.
Main Results:
- Morphine caused dose-dependent respiratory depression (hypoxia, hypercapnia, acidosis).
- Verapamil attenuated and delayed morphine's respiratory effects.
- Verapamil significantly reduced blood pressure, an effect seen even with combined administration.
- Verapamil antagonized morphine-induced tachycardia.
Conclusions:
- Verapamil mitigates morphine's respiratory depressant effects in rats.
- The interaction of verapamil with morphine's respiratory actions differs from its effects on antinociception and hypothermia.
- These findings suggest complex pharmacological interactions between verapamil and morphine.