Question

Head drop method is used in the bioassay of _______

• A. \( \text{Adrenaline} \)
• B. \( \text{Digoxin} \)
• C. \( \text{Oxytocin} \)
• D. \( \text{D-tubocurarine} \)

Hint:

Remember "head drop" and "rabbit" when you think of the bioassay for neuromuscular blockers like D-tubocurarine.

Answer 1

The Correct Option is D

The head drop method is a classical bioassay used to determine the potency of neuromuscular blocking agents, such as D-tubocurarine. In this method, the loss of the righting reflex in rabbits, indicated by the inability to lift their head, is observed after the administration of the test substance. The dose required to produce head drop in 50% of the animals (ED50) is then compared with that of a standard preparation to determine the relative potency. This method relies on the curare-like effect of D-tubocurarine, which causes skeletal muscle relaxation, including the neck muscles responsible for maintaining head posture.