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).