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Abstract
Pulmonary arterial hypertension is the most commonly recognized form of pulmonary hypertension in canines. Persistent pulmonary hypertension is a life-threatening; condition in neonatal foals. Treatment of pulmonary hypertension in both canines and neonatal foals has focused on the correction of hypoxia and acidosis, not on the pulmonary hypertension itself. Identification of pulmonary hypertension in canines and foals has been made easier with the new diagnostic technologies that are being employed by veterinarians. Although retrospective reviews and studies have been published on the use of sildafenil, which is used primarily for the treatment of human erectile dysfunction, to treat pulmonary hypertension in human neonates, and the pharmacodynamics of sildenafil have been examined in various species, sildenafil has not been used widely in dogs or foals. Therefore, the adverse effects of sildafenil in canines and foals have not been determined. Until the stability of sildenafil in suspension has been determined, it is recommended that dose-specific capsules be prepared by compounding pharmacists utilizing lactose as a diluent and that veterinarians be encouraged to prescribe small quantities of capsules until a maintenance dose has been achieved.
Advances in human medical therapy are often extrapolated to veterinary patients with hopes of achieving similar positive results. Interestingly, human drugs may be used in animals for indications other than the primary indication for which the drug is labeled in humans. The drug sildenafil (Viagra), for example, a phosphodiesterase-5 (PDE5) inhibitor used primarily to treat erectile dysfunction in humans, is now being used to treat cardiovascular conditions in dogs and neonatal foals. Recent case studies have reported using PDE5 inhibitors in dogs to treat pulmonary arterial hypertension (PAH), and in neonatal foals to treat persistent pulmonary hypertension at birth. The PDE5 inhibitors include sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra), although clinical experience with PDE5 inhibitors in animals is currently limited to sildenafil.
Pulmonary Hypertension
Pulmonary hypertension is defined as increased blood pressure in the pulmonary vascular system. In dogs, PAH is the most commonly recognized form and often is associated with heartworm infection. The mechanical and immunologic effects of the worms can lead to various degrees of increased pulmonary vascular resistance and pressure.
Identifying the presence of pulmonary hypertension has become easier with new diagnostic technologies used by veterinarians....