There is a risk of interaction between minoxidil and some medications including tadalafil, sildenafil, avanafil, and vardenafil. Systemic absorption of topical minoxidil is minimal in most patients when used as directed, however it is possible to absorb in the bloodstream and occasionally produce cardiovascular side effects such as decreases in blood pressure, swelling, and palpitation. Other medications that can also have these effects, when combined with minoxidil, can increase the risk. Signs of interaction may manifest as headaches, dizziness, lightheadedness, fainting, and or changes in pulse or heart beat. As always, seek medical attention from your healthcare provider or dermatologist in the event of unwanted side effects.