An 8 year old child is brought to emergency after accidently swallowing multiple tablets of a drug. The child developed severe diarrhea, urination, sweating and respiratory difficulty. On examination, pupil was constricted and there were crepitations heard on lung auscultation in lower lobes of both lungs. There were no vascular or CNS effects. Which drug can cause these type of effects?

**Core Concept**
The clinical presentation suggests an overdose of a drug that affects the parasympathetic nervous system, leading to increased cholinergic activity. This is characterized by symptoms such as diarrhea, urination, sweating, and respiratory difficulty, which are indicative of **muscarinic receptor** stimulation.

**Why the Correct Answer is Right**
The correct answer is likely an **organophosphate** or a **cholinesterase inhibitor**, which increases acetylcholine levels in the synaptic cleft, leading to overstimulation of **muscarinic** and **nicotinic receptors**. However, the absence of vascular or CNS effects suggests a more selective effect on muscarinic receptors, which are involved in the regulation of smooth muscle, glands, and the heart.

**Why Each Wrong Option is Incorrect**
**Option A:** May not be directly related to the specific symptoms described, lacking the characteristic cholinergic toxicity profile.
**Option B:** Could be considered, but the specific effects mentioned do not perfectly align with the expected toxicity profile.
**Option C:** May cause different types of toxicity, not matching the muscarinic-dominated picture presented.
**Option D:** Could potentially cause such effects, but without more context, it's less directly implicated in the described scenario.

**Clinical Pearl / High-Yield Fact**
In cases of suspected cholinergic toxicity, it's crucial to remember the mnemonic **SLUDGE** (Salivation, Lacrimation, Urination, Diarrhea, Gastrointestinal distress, and Emesis) to quickly identify key symptoms, although this case presents a slightly different constellation of symptoms.

**Correct Answer:** D. Organophosphate poisoning.

✓ Correct Answer: B. Neostigmine