Use of prazosin with other blood pressure lowering medicines or water pills may cause an additive blood pressure lowering effect.
Use of phosphodiesterase-5 (PDE-5) inhibitors, for example, sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra) with prazosin can also cause an additive decrease in blood pressure. To decrease the risk of precipitating side effects associated with low blood pressure, the lowest possible dose of PDE-5 inhibitors should be used in patients taking prazosin.
PREGNANCY: There are no adequate and well controlled studies of prazosin use in pregnancy. Prazosin should be used during pregnancy only if the potential benefit justifies the potential risk to the mother and the unborn baby. Prazosin is classified as FDA pregnancy risk category C (adverse effects in animals but inadequate data in humans).
NURSING MOTHERS: Small amounts of prazosin were found in human milk after oral administration. Due to the lack of conclusive safety data, prazosin should be used cautiously in nursing mothers.
REFERENCE: FDA Prescribing Information.
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