Tubocurarine

Emma Farrell

UNDER REVIEW (September 2016)

Mechanism of Action:

Tubocurarine is a plant alkaloid that, although not used clinically in the modern era is a prototype for other drugs that block the neuromuscular junction. It is a slow onset, long-acting, non-depolarizing blocker. It is a competitive antagonist of acetylcholine (ACh) acting at nicotinic acetylcholine receptors (nAChR). It blocks postsynaptic nAChRs, preventing action potential transmission and thus causing skeletal muscle relaxation. This sort of block can be overcome by increasing the relative concentration of ACh (e.g. by administration of an anti-cholinesterase such as neostigmine). Atracurium is another neuromuscular blocking drug that binds to the same site as ACh preventing the activation of the receptor-channel complex.

Lecture and CAL materials:

Drug specifics

Alternative drug name not specified
Effects Indsuces motor paralysis (of skeletal muscle), muscle relaxant, for induction of neuromuscular blockade in prior to intubation and anaesthesia. The neuromuscular blockade allows reduced anaesthetic doses since the anaesthetic itself does not have to be profound enough to relax muscles.
Adverse actions Hypotension, resulting from ganglion block and release of histamine from mast cells (not connected with nicotinic receptors; common side effect of strongly basic drugs). Bronchoconstriction in some individuals, result of histamine release.
Dose Not generally used clinically in the UK.
Interactions Not generally used clinically in the UK.
Contraindications not specified
Comments Tubocurarine was a prototypic drug, and is rarely used clinically any longer, though other safer synthetic drugs with similar modes of action have been developed, for example atracurium. Atracurium binds to the same site as ACh, preventing the activation of the receptor-channel complex. This non-depolarizing block can be overcome by increasing the relative concentration of ACh (e.g. by administration of an anti-cholinesterase such as neostigmine).
Contributors