HydralazineDose, contraindications and adverse effects for Dogs and Horses.

Direct-acting arteriolar vasodilator; reduces afterload in congestive heart failure. The primary uses of hydralazine in veterinary medicine have been as an afterload reducer in patients with congestive heart failure (CHF) or aortic valve disease. By reducing peripheral vascular resistance, hydralazine promotes forward left ventricular stroke volume and reduces the mitral regurgitant fraction. Hydralazine is not particularly useful in treating heart failure when myocardial diseas

Hydralazine is a direct systemic arterial vasodilator, which acts upon vascular smooth muscle and reduces peripheral resistance and blood pressure (BP). Hydralazine is a semicarbazide-sensitive amine oxidase (SSAO) inhibitor.

Hydralazine is contraindicated in patients that are hypersensitive to it. The drug is listed as contraindicated in human patients with mitral valvular rheumatic disease, but it has been recommended for use in small animal patients with myxomatous mitral valve disease. It is not recommended to use the drug in patients with hypovolemia or pre-existing hypotension. Hydralazine doses need to be titrated upwards carefully, as severe hypotension can result.

The most prevalent adverse effects seen in small animals are hypotension, weakness, lethargy, and syncope, particularly when doses are increased too fast. Reflex tachycardia, sodium and water retention, and GI distress (eg, vomiting, diarrhea) can also occur. Reflex sinus tachycardia may be treated with beta-blockers; however, caution must be exercised due to the risk for reduced cardiac performance.

■ Baseline thoracic radiographs ■ Clinical signs of CHF (eg, exercise intolerance, cough, increased resting respiratory rate and effort, mucous membrane color) ■ Hydration status, urine output ■ Serum electrolytes ■ If possible, arterial blood pressure and venous PO2.