Long-lasting canine cardiovascular alterations following bromocriptine induced-estrus

Bromocriptine (BRM), a dopamine 2 receptor agonist, is a common drug for inducing estrus in dogs. It is also used for the treatment of some endocrine abnormalities and has some cardiovascular consequences in the patients under treatment. The current study aimed to evaluate its effects on the cardiovascular function of dogs during administration and the subsequent induced estrus cycle. Eight non-pregnant female dogs were assigned into control and treatment groups. The control group (n = 3) were dogs that showed proestrus naturally. The treatment group (n = 5) received oral incremental (μg/kg) doses (100 on days 1 and 2, 200 on days 3, 4, and 400 on days 5 until the proestrus expression) of BRM tablets (2.5 mg; Iran-Hormone Co, Iran). The left ventricle function, carotid blood flow indices, and systolic (SAP) and diastolic (DAP) arterial pressure were recorded every two days. The phases of the cycle were determined using a vaginal smear. Peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistance index (RI) had a sharp decline following the administration of BRM (P < 0.05). The carotid PSA, EDV, RI, and pulse index were lower during induced estrus compared to the control (p < 0.05). BRM-induced estrus showed a different pattern of changes compared to the normal cycle from day 9 (p < 0.05) onwards. The cardiovascular effects of BRM remained for days after the termination of administration which may interfere with reproductive functions.