**Core Concept**
Phenytoin is an antiepileptic medication that can cause various adverse effects with chronic use, particularly in patients with seizure disorders. The mentioned effects are characteristic of phenytoin toxicity, which affects multiple organ systems.

**Why the Correct Answer is Right**
Phenytoin's adverse effects are primarily due to its interference with folate metabolism, leading to decreased folate levels. This results in increased homocysteine levels, which can cause osteomalacia (softening of bones) and other systemic effects. Additionally, phenytoin is known to cause gingival hyperplasia (overgrowth of gum tissue) due to its effect on vitamin D metabolism and calcium absorption. Hirsutism (excessive hair growth) and coarsening of facial features are also observed in patients with chronic phenytoin use.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the adverse effects described are not characteristic of carbamazepine, another antiepileptic medication. While carbamazepine can cause various side effects, the specific combination mentioned is more typical of phenytoin.
**Option B:** This option is incorrect because valproic acid is associated with a different set of adverse effects, including hepatotoxicity, teratogenicity, and weight gain.

**Clinical Pearl / High-Yield Fact**
The "folic acid antagonism" caused by phenytoin can be mitigated by supplementing with folic acid, which can help prevent or reduce the severity of osteomalacia and other related adverse effects.

**Correct Answer:** D. Phenytoin.