Vetnuus | November 2025 45 Regulars I Dental Column Veterinary Dentistry and Maxillofacial Surgery Referrals Veterinary Dentistry and Maxillofacial Clinic, Private Bag X04, Onderstepoort, 0110 Veterinary Dentistry and Maxillofacial Clinic, Onderstepoort Veterinary Academic Hospital, Faculty of Veterinary Science, University of Pretoria, Old Soutpan Road (M35), Onderstepoort, South Africa Tel: +27 (0)12 529 8276, Fax: +27 (0) 12 529 8479, e-mail: sadent@mweb.co.za, website: www.vetdentsa.co.za, Facebook: Vetdent SA Biopsy of a lesion should be considered if the overgrowth is asymmetrical, ulcerated, proliferative, or inconsistent with expected drug effects, in order to rule out neoplasia. Pathogenesis of Drug-Induced Gingival Hyperplasia The exact pathogenesis of drug-induced gingival hyperplasia in dogs and cats remains unclear. The following mechanisms have been described in humans: • Anticonvulsants (Phenytoin): Some individuals may have genetically distinct fibroblasts that respond abnormally to phenytoin, leading to excessive connective tissue accumulation. Reduced collagen breakdown in the gingiva may also contribute. • Calcium channel blockers (e.g. Amlodipine): Activation of gingival fibroblasts results in connective tissue accumulation. In addition, decreased matrix metalloproteinase (MMP) activity reduces protein degradation. • Immunosuppressants (Cyclosporine): The primary metabolite hydroxycyclosporine, together with cyclosporine itself, stimulates fibroblast proliferation (Beaumont et al., 2017). Drug-induced gingival hyperplasia in cats is extremely rare. Apart from single case reports in cats receiving cyclosporine (Latimer et al) and in cats treated with calcium channel blockers (Desmet et al), very little has been published. While uncommon, the condition is increasingly recognised as more geriatric cats are maintained on long-term antihypertensive medication. Hyperplasia typically develops at higher dosages of amlodipine. Clinical Management Drug-induced gingival hyperplasia usually resolves after discontinuation of the offending drug. In a case report by Desmet and van der Meer (2017), a cat developed gingival hyperplasia within 5 months of starting amlodipine. Due to the severity, amlodipine was substituted with telmisartan to control hypertension. The cat was gradually weaned off amlodipine, and the gingival hyperplasia resolved completely within a few months. Treatment and monitoring recommendations include: • Drug substitution: If feasible, switch to an alternative medication (e.g., telmisartan instead of amlodipine) when gingival hyperplasia is significant. • Surgical intervention: Gingivectomy may be required in severe cases where drug withdrawal is not possible or resolution is delayed, to prevent progression of periodontitis. • Dental care: Professional prophylaxis, plaque control, and diligent home care reduce secondary periodontal complications. • Monitoring: Oral examinations should be incorporated into long-term treatment plans for cats receiving medications associated with gingival hyperplasia. Although drug-induced gingival hyperplasia is relatively uncommon in cats, it is important to recognise the presentation, particularly in patients treated with amlodipine for systemic hypertension. Incorporating routine oral assessments into chronic disease management, together with owner education and timely therapeutic adjustments, allows early intervention and improves patient welfare. v References Beaumont, J., Chesterman, J., Kellett, M. & Durey, K. (2017). Gingival overgrowth: Part 1: Aetiology and clinical diagnosis. British Dental Journal, 222, 85–91. Beckman, B. Gingival Hyperplasia in Dogs: Surgical and Medical Management Strategies for Veterinarians. Desmet, L. & Van der Meer, J. (2017). Antihypertensive treatment with telmisartan in a cat with amlodipine-induced gingival hyperplasia. Journal of Feline Medicine and Surgery Open Reports, 3, 2055116917745236. Latimer, K.S., Rakich, P.M., Purswell, B.J., & Kircher, I.M. (1986). Effects of cyclosporin A administration in cats. Veterinary Immunology and Immunopathology, Volume 11, Issue 2, February 1986, Pages 161-173 Nishikawa, S., Nagata, T., Morisaki, I., Oka, T. & Ishida, H. (1996). Pathogenesis of drug-induced gingival overgrowth: A review of studies in the rat model. Journal of Periodontology, 67, 463–471.
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