**Core Concept**
Thalidomide is a sedative-hypnotic agent that has been used for the treatment of insomnia and anxiety. However, it has been associated with severe adverse effects, primarily due to its teratogenic properties and immunomodulatory effects.

**Why the Correct Answer is Right**
Thalidomide is known to cause peripheral neuropathy, which is a result of its toxic effects on the dorsal root ganglia. This leads to degeneration of the peripheral nerves, causing symptoms such as pain, numbness, and weakness in the extremities. Additionally, thalidomide can cause constipation due to its anticholinergic effects, which slow down gut motility. Sedation is also a common adverse effect of thalidomide, as it acts on the central nervous system to produce a hypnotic effect. However, myocarditis is not a known adverse effect of thalidomide.

**Why Each Wrong Option is Incorrect**
**Option B:** Constipation is a known adverse effect of thalidomide, primarily due to its anticholinergic effects.
**Option C:** Peripheral neuropathy is a well-documented adverse effect of thalidomide, resulting from its toxic effects on the dorsal root ganglia.
**Option D:** Sedation is a common adverse effect of thalidomide, as it acts on the central nervous system to produce a hypnotic effect.

**Clinical Pearl / High-Yield Fact**
Thalidomide is a classic example of a drug with a "black box" warning due to its severe teratogenic effects. It is essential for healthcare providers to take adequate precautions when prescribing thalidomide, including proper patient education and counseling.

**✓ Correct Answer: A. Myocarditis. Myocarditis is not a known adverse effect of thalidomide.**