**Core Concept**
Phenytoin is a widely used antiepileptic medication that exhibits non-linear pharmacokinetics due to its saturable metabolic pathway. This unique characteristic affects its clearance and half-life in a dose-dependent manner.

**Why the Correct Answer is Right**
Phenytoin primarily undergoes hepatic metabolism, which is mediated by the cytochrome P450 enzyme system. At lower concentrations, phenytoin is metabolized by this enzyme system in a first-order manner, following linear kinetics. However, as the concentration of phenytoin increases, the enzyme system becomes saturated, leading to a decrease in the rate of metabolism. This results in a non-linear increase in plasma concentrations, and the drug follows zero-order kinetics. This phenomenon is known as "saturation kinetics."

**Why Each Wrong Option is Incorrect**
**Option A:** Phenytoin is actually an enzyme inducer, but its effect is relatively weak compared to other antiepileptic drugs. It is not a potent microsomal enzyme inducer like rifampicin or carbamazepine.
**Option B:** Phenytoin is highly bound to plasma proteins, primarily albumin, which affects its free fraction and pharmacological activity. This high protein binding is a critical pharmacokinetic property of phenytoin.
**Option D:** With increasing dose, the clearance of phenytoin actually decreases, leading to an increase in plasma concentrations and half-life. This is due to the saturation of the metabolic pathway, as explained earlier.

**Clinical Pearl / High-Yield Fact**
Phenytoin's non-linear pharmacokinetics can lead to a significant increase in plasma concentrations with small dose increments, resulting in potential toxicity. This is why it is essential to monitor plasma concentrations and adjust dosages carefully to avoid adverse effects.

**✓ Correct Answer: C. At lower concentration it follows zero order kinetics**