Non depolarizing muscle relaxants are potentiated by all except
**Core Concept**
Non-depolarizing muscle relaxants (NDMRs) are a class of drugs that inhibit neuronal transmission at the neuromuscular junction (NMJ), leading to muscle paralysis. Their potency can be influenced by various factors, including the presence of other substances that either enhance or inhibit their action.
**Why the Correct Answer is Right**
The potency of NDMRs is known to be enhanced by substances that increase the concentration of calcium ions (Ca2+) in the neuromuscular junction. Calcium ions play a crucial role in the release of acetylcholine (ACh) from the motor neuron terminal. When calcium ions are present in higher concentrations, more ACh is released, increasing the likelihood of muscle contraction and, consequently, the effect of NDMRs. **Succinylcholine**, a depolarizing muscle relaxant, is a well-known potentiator of NDMRs.
**Why Each Wrong Option is Incorrect**
**Option A:** **Potassium** does not directly affect the neuromuscular junction and is not a known potentiator of NDMRs.
**Option B:** **Magnesium** is actually a known inhibitor of NDMRs, as it can block the release of acetylcholine from the motor neuron terminal.
**Option C:** **Curare** is a natural NDMR and is not a potentiator, but rather a competitor at the nicotinic acetylcholine receptor.
**Clinical Pearl / High-Yield Fact**
When administering NDMRs, it is essential to be aware of the potential for potentiation by substances that increase calcium ion concentrations, such as **succinylcholine**.
**Correct Answer:** B. Magnesium