**Core Concept**
Forced diuresis is a medical treatment used to enhance the elimination of certain toxins and drugs from the body by increasing urine production and manipulating urine pH. Alkalization of the urine can increase the elimination of weak acids, while acidification can increase the elimination of weak bases.

**Why the Correct Answer is Right**
Phenobarbitone is a weak acid that can be effectively eliminated from the body through alkaline diuresis. By increasing the pH of the urine, phenobarbitone becomes more ionized and is more readily excreted by the kidneys. This is because the kidneys are more efficient at removing ionized substances from the body, and the higher pH of the urine favors the ionization of weak acids like phenobarbitone. This mechanism is particularly useful in cases of phenobarbitone overdose, where rapid elimination of the drug is necessary to prevent severe toxicity.

**Why Each Wrong Option is Incorrect**
**Option A:** Amphetamines are weak bases and are more effectively eliminated through acidification of the urine, not alkalization.

**Option C:** Phencyclidine is also a weak base and is more effectively eliminated through acidification of the urine.

**Option D:** Theophylline is a weak base and is more effectively eliminated through acidification of the urine.

**Clinical Pearl / High-Yield Fact**
When managing cases of phenobarbitone overdose, alkaline diuresis can be an effective treatment strategy to enhance elimination of the drug and prevent severe toxicity. This is a key concept in forensic medicine and toxicology.

**✓ Correct Answer: B. Phenobarbitone**