Toxicity in Doberman Pinchers with ventricular arrhythmias treated with amiodarone (1996-2005).

BACKGROUND: Asymptomatic Doberman Pinschers with dilated cardiomyopathy (DCM) often die suddenly owing to ventricular tachycardia that degenerates into ventricular fibrillation. A safe and effective antiarrhythmic drug treatment is needed. This will require a large, well-controlled, prospective study. HYPOTHESIS: Amiodarone toxicity is common in Dobermans with occult DCM and ventricular tachyarrhythmias refractory to antiarrhythmia therapy. Infrequent monitoring of hepatic function is inadequate. Frequent monitoring may be useful to determine dogs in which the dosage should be decreased or the drug withdrawn. METHODS: Medical records from the University of Georgia and Cornell University were searched for Doberman Pinschers diagnosed with preclinical DCM that received amiodarone for severe ventricular arrhythmias refractory to other antiarrhythmic agents. Echocardiographic data, Holter recording data, hepatic enzyme serum activity, and serum amiodarone concentrations were recorded. The presence of clinical signs of toxicity was recorded. Serum amiodarone concentrations were obtained in some dogs. RESULTS: Reversible toxicity was identified in 10 of 22 (45%) dogs. CONCLUSION AND CLINICAL IMPORTANCE: Adverse effects from amiodarone were common and were, in part, dosage related. Patients should be monitored for signs of toxicity and liver enzyme activity should be measured at least monthly.

Gingival hyperplasia associated with the administration of amlodipine to dogs with degenerative valvular disease (2004-2008).

BACKGROUND: Calcium channel blocking drugs, usually nifedipine and less often amlodipine, have been reported to cause gingival hyperplasia (GH) in humans. HYPOTHESIS: Amlodipine, a dihydropyridine calcium channel blocking drug, can cause GH when administered chronically to older small dogs with degenerative valvular disease. ANIMALS STUDIED: From January 2004 to May 2008, 82 client-owned dogs with degenerative valvular disease and left atrial dilatation were treated with amlodipine in combination with spironolactone and enalapril and followed for >6 months. METHODS: Retrospective study. A chronological observation of GH in 2 dogs treated with amlodipine in 2004 and 2006 prompted the study. Patient histories and medical records of each dog treated with amlodipine for degenerative valvular disease from January 2004 to May 2008 were reviewed. RESULTS: GH was observed by clients and the authors in 7 of 82 (8.5%) dogs. Histologic confirmation of the diagnosis was made in 2 dogs. The minimum duration of treatment before diagnosis of GH was 5 months. GH began to resolve within 2 weeks of discontinuing amlodipine and resolution was complete within 6 months. Amlodipine administration was reinstituted in 1 dog in which GH had resolved, and GH reoccurred within 4 months. CONCLUSION AND CLINICAL IMPORTANCE: Long-term administration of amlodipine to dogs with degenerative valvular disease may cause GH in a small percentage of patients. GH resolves quickly after withdrawal of amlodipine treatment.