Although rare, Viagra (sildenafil), Cialis (tadalafil) and Levitra (
vardenafil) can cause muscle pain and unusual skin sensations or paresthesia. In clinical studies, Viagra caused muscle pain and paresthesia in less than 2% of patients. Patients who experience these side effects should stop taking the medication and consult their physician. These medications increase blood flow to the penis by inhibiting the enzyme phosphodiesterase type 5 (PDE5).