Related Experiment Video
Updated: May 10, 2026
Intracranial Pharmacotherapy and Pain Assays in Rodents
Published on: April 9, 2019
Pharmacokinetics of intramuscularly administered morphine in horses
Elizabeth P Devine1, Butch KuKanich, Warren L Beard
1Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66502, USA. devine@vet.k-state.edu
Objective:
To determine the pharmacokinetics of morphine after IM administration in a clinical population of horses.
Design:
Prospective clinical study.
Animals:
77 horses.
Procedures:
Morphine sulfate (0.1 mg/kg [0.045 mg/lb], IM) was administered to horses, and blood samples were obtained at predetermined time points. Plasma morphine concentrations were measured via liquid chromatography and mass spectrometry. In preliminary investigations, samples were obtained from 2 healthy horses at 12 time points (up to 12 hours after drug administration) and analyzed via 2-stage pharmacokinetic analysis. In the clinical phase, blood samples were obtained from 75 hospitalized horses at various times (total, 2 to 3 samples/horse) up to 9 hours after drug administration, and data were analyzed via a naïve pooled pharmacokinetic model.
Results:
In the clinical phase, the apparent terminal half-life (t(½)) of morphine was approximately 1.5 hours, volume of distribution per bioavailability was approximately 4.5 L/kg, and clearance per bioavailability was approximately 35 mL/kg/min. Peak plasma concentration in naïve pooled analysis was 21.6 ng/mL and occurred approximately 4 minutes after administration. Morphine concentrations were below the limit of quantification ≤ 7 hours after administration in 74 horses. Adverse effects attributed to morphine administration were uncommon and considered mild.
Conclusions And Clinical Relevance:
The short t(½) of morphine in horses suggested frequent administration may be needed to maintain targeted plasma concentrations. Variations in plasma concentrations suggested optimal dosages may differ among horses. The drug was well tolerated at the described dose, but patients receiving morphine should be monitored carefully.
More Related Videos
07:23Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
08:51Multiple Intravenous Bolus Dosing and Invasive Hemodynamic Assessment in a Hypoxia-Induced Mouse Pulmonary Artery Hypertension Model
Published on: November 11, 2022
Related Concept Videos
01:25Routes of Drug Administration: Parenteral
The intravenous route (IV) of drug administration can be further categorized into two types. The bolus injection administers the entire dose rapidly, while an intravenous infusion slowly delivers smaller doses steadily.
The IV route is often...
01:15Opioid Analgesics: Synthetic and Semisynthetic Opioids
01:11Nondepolarizing (Competitive) Neuromuscular Blockers: Pharmacokinetics
Instead, they are transported by the blood to different tissues. Muscles with a greater blood supply (arteries) and blood flow receive more...
01:21Drug Accumulation During Multiple Dosing: Repetitive IV Injections
01:19One-Compartment Open Model for IV Bolus Administration: General Considerations
The drug's presence in the body is defined by an equation representing the difference between the rates of drug entry and exit. Key parameters—elimination rate constant, half-life,...
00:59Nonlinear Pharmacokinetics: Drug Elimination for IV Bolus Injection
Following the administration of a single intravenous (IV) bolus injection, we can determine the concentration of the drug in the plasma at any given time. This calculation is achieved using a specific equation that integrates the values of Vmax and KM.
We can also...