[How do we explain the antihypertensive effect of bromocriptine? Clinical and experimental contribution]

The mechanism of the antihypertensive properties of bromocriptine was investigated in dog and man. In anaesthetized dogs, bromocriptine induced a decrease in the pressor responses to adrenaline or phenylephrine and reduced the hypotensive properties of clonidine. In 6 hypertensive patients with Parkinson's disease, chronic treatment with bromocriptine (46.4 +/- 12.0 mg/day) elicited both a significant decrease in blood pressure and an improvement of extrapyramidal symptoms. During bromocriptine therapy, domperidone (60 mg/day during 1 month), a specific peripheral dopaminergic antagonist was introduced. The drug did not change the levels of blood pressure (before domperidone: 150.8 +/- 22.5/79.9 +/- 8.9 mmHg after domperidone: 150 +/- 17.3/87.5 +/- 12.9 mmHg). These results confirm the antihypertensive properties of bromocriptine and demonstrate that, beside their dopaminergic properties, the drug also possesses mixed alpha 1 and alpha 2 adrenolytic actions. These two properties may contribute to the mechanism of the antihypertensive effects of bromocriptine. These data also show that domperidone can be used in bromocriptine-treated hypertensive parkinsonians without side effects on blood pressure.