**Question:** Features of strychnine poisoning -

A. Muscle rigidity and fasciculations
B. Seizures
C. Tremors
D. Respiratory depression

**Correct Answer:** A. Muscle rigidity and fasciculations

**Core Concept:** Strychnine is an alkaloid found in plants like Strychnos nux-vomica, which is the source of the drug used to poison snakes and rodents. Strychnine poisoning is characterized by its effects on the central nervous system (CNS) and the skeletal muscles.

**Why the Correct Answer is Right:** Strychnine acts as a competitive antagonist at the glycine receptors in the spinal cord, leading to increased excitatory drive from the motor neurons. This results in muscle rigidity and fasciculations. Fasciculations are involuntary contractions of muscle fibers, usually observed as tremors or twitching.

**Why Each Wrong Option is Incorrect:**

B. Seizures: Strychnine does not cause seizures directly but rather leads to muscle rigidity and fasciculations, which may co-exist with seizures in some cases.

C. Tremors: While tremors can be observed in strychnine poisoning, the primary features are muscle rigidity and fasciculations.

D. Respiratory depression: Although strychnine can cause respiratory depression, the primary feature is muscle rigidity and fasciculations.

**Clinical Pearl:** Strychnine poisoning is a classic example of a neuroleptic malignant syndrome (NMS), a severe and potentially fatal complication of neuroleptic drug therapy. It is important for clinicians to recognize these features to initiate appropriate treatment and prevent further complications.