If the blood pressure medication seems to be responsible for his erectile dysfunction, a change of medicine of hypertension should be the first step. Medications are quite common cause of these and especially in youngs like your husband. Consulting a urologist would be the next step. Getting a colored doppler study, would be the third step and hormonal evaluation like measurement of luteinizing hormone, serum prolactin level and serum testosterone levels would be the final step.
Please feel free for your follow up questions.
Going to a cardiologist (heart doctor) would be the better option for managing the antihypertensive medications. I would suggest you to first stop the metoprolol, as it has maximal potential for the erectile dysfunctions. Adding an alpha receptor blocker at the night time may help him controlling the blood pressure as well getting rid of the side effect of erection.
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My best wishes and kindest regards XXXXX XXXXX of you.