Which of the following medications can cause gingival hyperplasia?

Gingival hyperplasia is a condition characterized by an overgrowth of gum tissue, and one of the well-recognized medications that can induce this condition is phenytoin. Phenytoin, an anticonvulsant commonly used to manage seizures, can stimulate the proliferation of gingival fibroblasts in some individuals, leading to the excessive growth of gum tissue.

The mechanism behind this side effect is not fully understood but is thought to involve changes in the local environment of the gums, including alterations in the balance of growth factors and a response to the medication that causes tissues to grow more than they normally would. Clinicians often monitor patients on phenytoin therapy for signs of gingival hyperplasia and may recommend improved oral hygiene practices or adjustments in therapy to mitigate this effect.

The other medications listed do not typically cause gingival hyperplasia. For example, while amoxicillin and ciprofloxacin are antibiotics and can have various side effects, they are not associated with gum overgrowth. Ranitidine, a medication used to reduce stomach acid, is also not known to cause gingival hyperplasia. Therefore, phenytoin's association with this particular oral health issue makes it the correct choice in this context.