Just a few options off the top of my head.
1) Exogenous Depression. The onset of his depression began coincides with a distinct stressor -- sudden loss of his livelihood, purpose, and possibly chronic pain. His depression is, in some ways, understandable. Who wouldn't be depressed? This situation doesn't mean he won't respond to medications, but rather than simply focusing on the depressive symptoms, treating his pain, helping him find a new job, and rediscovering meaning could be just as important to his prognosis. Now I know primary care is strapped in time -- recommend a therapist, if possible and if he's receptive.
2) You may be able to back down on the Lexapro dosage and see if the sexual side effects improve. 20 to 15? 15 to 10? The issue is here is that he may need more medication for his depression. You also may ask him to take the medication after intercourse, as timing may affect the sexual function.
3) Augment the Lexpapro with Wellbutrin. In this case, it may bring the depression to full remission and also treat the sexual side effects. Wellbutrin works in a different way than SSRIs, so you won't be worsening the serotonin effects. There is a little evidence that Trazodone may also help with sexual side effects.
4) SNRIs are also likely to cause sexual side effects but may be worth a try. A possibility is to stop the Lexapro and start Cymbalta. If the patient has chronic pain that's resistant to treatment and affecting his mood, the norepinephrine effects from an SNRI may be useful.
