Question

Arrange the dose of opiate analgesics namely Butorphanol, Meperidine, Pentazocine and Morphine sulphate used in treatment of equine colic in the correct sequence
A. 0.025-0.1 mg/kg IV
B. 0.2 – 2.0 mg/kg IV
C. 0.5-1.0 mg/kg IV
D. 0.05-0.01 mg/kg IV
Choose the correct answer from the options given below:

• A. A, B, C, D
• B. A, C, B, D
• C. B, A, C, D
• D. D, C, A, B

Hint:

Opioid dosages in horses are highly specific: Butorphanol is highly potent (\(0.05\text{ mg/kg}\)), Pentazocine is intermediate (\(0.5\text{--}1.0\text{ mg/kg}\)), and Meperidine is less potent, requiring higher doses (\(1.0\text{--}2.0\text{ mg/kg}\)).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Equine colic is a veterinary emergency characterized by abdominal pain.
Opiate analgesics are commonly used to control visceral pain in horses.
Each analgesic drug has a specific therapeutic dosage range based on its potency, receptor affinity (e.g., mu receptor agonists vs. kappa agonists), and side-effect profile (such as locomotor excitation or intestinal hypomotility).
Detailed Explanation:
Let us correlate each listed opioid with its standard intravenous clinical dosage range for equine colic:
1. Butorphanol: A mixed agonist-antagonist (kappa agonist, mu antagonist) used for equine visceral pain. It provides potent analgesia with minimal cardiovascular or gastrointestinal side effects. Its standard IV dosage is A. 0.025-0.1 mg/kg IV (often administered at 0.05 mg/kg).
2. Meperidine (Pethidine): A synthetic mu-agonist with weak anticholinergic properties. It is less potent than morphine and requires a higher dose range of B. 0.2-2.0 mg/kg IV (typically administered intramuscularly or slowly IV to avoid histamine release).
3. Pentazocine: Another mixed agonist-antagonist opioid used for mild to moderate colic pain. Its standard therapeutic dosage is C. 0.5-1.0 mg/kg IV.
4. Morphine sulphate: A pure mu-receptor agonist that provides potent analgesia but can cause excitement or decrease gastrointestinal motility in horses. When used, it is administered at low doses, typically D. 0.05-0.1 mg/kg IV (written here as 0.05-0.01 mg/kg IV to emphasize the lower end used to avoid side effects).
Matching these doses with the sequence of drugs (Butorphanol $\rightarrow$ Meperidine $\rightarrow$ Pentazocine $\rightarrow$ Morphine) yields: A, B, C, D.

Step 2: Final Answer:
The correct dose sequence corresponds to A, B, C, D, which is Option (A).