**Question:** Adverse effects of phenytoin include all of the following except?

A. Hypersensitivity reactions
B. Drowsiness
C. Increased appetite
D. Seizures

**Core Concept:** Phenytoin is an antiepileptic drug used for the treatment of epilepsy and is known to cause various adverse effects. These effects can be categorized into hypersensitivity reactions, CNS (Central Nervous System) effects, and gastrointestinal effects.

**Why the Correct Answer is Right:** Phenytoin-induced seizures is a direct contradiction to the drug's primary purpose of treating seizures. Therefore, seizures are not considered as an adverse effect of phenytoin.

**Why Each Wrong Option is Incorrect:**

A. Hypersensitivity reactions: Phenytoin can cause hypersensitivity reactions, such as rash and angioedema. These reactions are not specific to phenytoin alone but also occur with other drugs.

B. Drowsiness: Phenytoin can cause drowsiness as a side effect due to its CNS depressant action.

C. Increased appetite: Although phenytoin can cause weight gain, the specific increase in appetite is not typically mentioned as an adverse effect.

**Why Each Wrong Option is Incorrect:**

D. Seizures: As mentioned above, seizures are the primary indication of phenytoin use and not considered an adverse effect.

**Clinical Pearl:** Phenytoin's adverse effects need to be carefully monitored and managed in patients receiving this medication, ensuring that the potential benefits of treatment outweigh the risks.

**Correct Answer:** D. Seizures