Question

Arrange the half life (beta) in hours of single intravenous administration of gentamicin (10 mg/kg) in serum in hawks, owls, eagles and catfish, respectively
A. 1.35
B. 1.93
C. 2.46
D. 11.87

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

Hint:

To quickly solve this species-comparison question:
Identify the poikilothermic catfish as having the slowest metabolic clearance and thus the longest half-life (D: 11.87 h).
For the birds, smaller birds (hawks) have higher GFR and faster clearance than larger birds (eagles).
This places the order from fastest to slowest as: Hawk $\rightarrow$ Owl $\rightarrow$ Eagle $\rightarrow$ Fish (A, B, C, D).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The elimination half-life (\(t_{1/2}\beta\)) of a drug is heavily influenced by the metabolic rate and renal clearance of the species.
Homeothermic birds have very high metabolic and glomerular filtration rates, leading to rapid drug clearance, while poikilothermic (cold-blooded) animals like fish clear drugs much slower.

Step 2: Detailed Explanation:
Let us correlate the half-life values of gentamicin in the specified animal species:
- Smaller birds of prey with higher metabolic rates clear gentamicin fastest.
- In hawks (e.g., Red-tailed hawks), the elimination half-life is approximately 1.35 hours (A).
- In owls (e.g., Great Horned owls), the half-life is slightly longer, at 1.93 hours (B).
- In larger birds of prey like eagles (e.g., Bald eagles), it is approximately 2.46 hours (C).
- In poikilotherms like catfish, metabolic rate and renal clearance are temperature-dependent and substantially slower, resulting in a prolonged half-life of 11.87 hours (D).

Step 3: Final Answer:
The chronological order matching the species hawks, owls, eagles, and catfish respectively is A, B, C, D, which corresponds to option (A).