Reserpine can antagonize the inhibitory effects of anticholinergic agents on gastric acid secretion. The use of estrogens can increase fluid retention and increase blood pressure, thereby antagonizing the antihypertensive effects of reserpine. Concomitant use of reserpine with sympathomimetics, such as cocaine, dobutamine, dopamine, norepinephrine, epinephrine, metaraminol, methoxamine, phenylephrine, phenylpropanolamine, or ephedrine, can potentiate the vasopressor effects of these agents, antagonizing the antihypertensive effects of reserpine. The mechanism of this interaction is believed to involve reserpine-induced inhibition of the uptake of the sympathomimetic drug by adrenergic neurons, possibly resulting in hypertension and cardiac arrhythmias. Adverse CNS effects, including fatigue, dizziness, and drowsiness or lethargy, can occur during reserpine therapy.
Mental depression can potentially be severe and can occur in any patient receiving the drug.
Therapy should be discontinued if signs of depression are reported. Reserpine-induced depression can last for several months following discontinuance of the drug. Edema with fluid retention and dyspnea can occur with reserpine therapy, and eventually can lead to congestive heart failure. These adverse effects can be alleviated by concomitant administration of a diuretic. Reserpine can cause miosis, which is slight, but can last up to a week after a single dose.