American journal of veterinary research
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Comparative Study
Pharmacokinetics, pharmacodynamics, and analgesic effects of morphine after rectal, intramuscular, and intravenous administration in dogs.
To compare systemic bioavailability and duration for therapeutic plasma concentrations and cardiovascular, respiratory, and analgesic effects of morphine administered per rectum, compared with IV and IM administration in dogs. ⋯ Rectal administration of morphine did not increase bioavailability above that reported for oral administration of morphine in dogs. Low bioavailability and plasma concentrations limit the clinical usefulness of morphine administered per rectum in dogs.