**Core Concept**
The question is testing the knowledge of the anticholinergic side effects of certain medications, specifically the tricyclic antidepressants (TCAs). Amitriptyline is a TCA that can cause anticholinergic toxicity, leading to symptoms such as bradycardia, hypotension, decreased sweating, and salivation.

**Why the Correct Answer is Right**
Amitriptyline is a TCA that works by inhibiting the reuptake of serotonin and norepinephrine. However, one of its major side effects is anticholinergic toxicity, which occurs due to the blockade of muscarinic acetylcholine receptors. This blockade leads to decreased parasympathetic activity, resulting in bradycardia, hypotension, decreased sweating, and salivation. The anticholinergic effects of amitriptyline are more pronounced in overdose situations, where the drug can accumulate to toxic levels.

**Why Each Wrong Option is Incorrect**
**Option B:** Lithium is a mood stabilizer used in the treatment of bipolar disorder. It is not associated with anticholinergic toxicity and does not cause bradycardia, hypotension, decreased sweating, and salivation in overdose.

**Option C:** Selegiline is a monoamine oxidase B (MAO-B) inhibitor used in the treatment of Parkinson's disease and major depressive disorder. It does not have significant anticholinergic effects and is not associated with the symptoms described.

**Option D:** Amphetamine is a central nervous system stimulant used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. It does not cause anticholinergic toxicity and is not associated with bradycardia, hypotension, decreased sweating, and salivation.

**Clinical Pearl / High-Yield Fact**
In cases of suspected TCA overdose, it is essential to perform an ECG and monitor for cardiac arrhythmias, as TCAs can cause QT interval prolongation and cardiac conduction abnormalities. Additionally, patients with TCA overdose should be treated with supportive care, including activated charcoal administration and cardiac monitoring.

**✓ Correct Answer: A. Amitryptilline**