The antihypertensive medication most commonly associated with the development of gingival overgrowth is Amlodipine.

Gingival overgrowth, also known as gingival hyperplasia, is a well-documented adverse effect linked primarily to certain classes of drugs, including calcium channel blockers (CCBs), anticonvulsants, and immunosuppressants. Among calcium channel blockers, Amlodipine and Nifedipine are frequently implicated.

- Amlodipine is a dihydropyridine calcium channel blocker commonly used to manage hypertension and angina.
- It can induce fibroblast proliferation and increase extracellular matrix production in gingival tissues leading to the characteristic overgrowth.
- The onset of gingival overgrowth due to Amlodipine typically occurs within 1–3 months of drug initiation, although this can vary based on individual patient factors such as oral hygiene and genetic predisposition.
- Lisinopril (an ACE inhibitor), Hydrochlorothiazide (a thiazide diuretic), and Metoprolol (a beta-blocker) are not commonly associated with gingival overgrowth.

Key Points:
- Amlodipine is a calcium channel blocker that commonly causes gingival overgrowth.
- Gingival overgrowth is due to fibroblast stimulation and excess collagen deposition.
- Good oral hygiene and drug substitution can mitigate this side effect.
- Lisinopril, Hydrochlorothiazide, and Metoprolol are not typically linked to gingival hyperplasia.

References:
- Harrison's Principles of Internal Medicine, 20th Edition, Volume 2, Chapter on Pharmacology, Page 1294
- Robbins Basic Pathology, 10th Edition, Chapter 11: Disorders of the Immune System, Page 390