Difficulty achieving or sustaining penile erections can occur as part of obstructive sleep apnea (OSA). Patients with untreated OSA experience repeated drops in the oxygen level (hypoxemia) during sleep, and research suggests that this phenomenon negatively impacts erectile functioning. Moreover, some of the medications frequently used to treat problems with erectile functioning work by relaxing certain types of muscles in the body. One muscle group that may relax in response to these types of medications is located around the upper airway (or throat) area. The relaxation of the muscles around the upper airway can increase the upper airway’s propensity to collapse, causing an obstruction (or apnea) in the airway. As such, OSA may in some cases be worsened by the medications used to treat erectile dysfunction.