Phentolamine and Tadalafil interaction
Phentolamine and Tadalafil: the Tadalafil prescribing label flags this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Tadalafil (Cialis) label · effective 2026-06-03
CIALIS is not recommended in combination with alpha-blockers for the treatment of BPH because efficacy of the combination has not been adequately studied and because of the risk of blood pressure lowering.
Use of CIALIS with alpha-blockers, antihypertensives or substantial amounts of alcohol (≥5 units) may lead to hypotension ( 5.6 , 5.9 ).
Caution is advised when CIALIS is used as a treatment for ED in men taking alpha-blockers.
…Physicians should be aware that CIALIS for once daily use provides continuous plasma tadalafil levels and should consider this when evaluating the potential for interactions with medications (e.g., nitrates, alpha-blockers, anti-hypertensives and potent inhibitors of CYP3A4) and with substantial consumption of alcohol [see Drug Interactions ( 7.1 , 7.2 , 7.3 )] .
Caution is advised when PDE5 inhibitors are coadministered with alpha-blockers.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.