Bioassay of d-Tubocurarine

• Bioassay of d-Tubocurarine (ADH): Commonly done using frog rectus abdominis muscle.
• Bioassay of d-Tubocurarine (ADH): Measures neuromuscular blockade to assess potency.

Principle of Bioassay of d-Tubocurarine

• d-Tubocurarine is a non-depolarizing neuromuscular blocker that prevents acetylcholine from activating nicotinic receptors at the neuromuscular junction.
• The bioassay measures loss of muscle contraction (e.g., twitch response) in response to nerve stimulation.

Methods

 1. Frog Rectus Abdominis or Chick Biventer Cervicis Assay (In Vitro)

• Procedure:
  1. Mount the muscle in an organ bath, stimulate it electrically.
  2. Record the twitch height with standard d-tubocurarine added at increasing doses, then wash and repeat with test sample.
• Potency Determination: Compare the concentration needed to reduce the twitch by 50

2. Mammalian (e.g., Rat) Nerve-Muscle Preparation (In Vivo)

• Procedure:
  1. Anesthetize rat, stimulate the sciatic nerve, measure the twitch response of the gastrocnemius muscle.
  2. Administer standard and test preparations of d-tubocurarine in incremental doses, noting the blockade of muscle twitch.
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• Potency Determination: Compare dose-response blockade curves.

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