Brief Answer:
You can try PDE5 Inhibitors

Detailed Answer:
Hi,
Eligard works against prostate cancer by medically reducing serum testosterone levels. At a time when we are intentionally reducing serum testosterone levels, it would be difficult to expect that erections would be normal, but some patients have tried and achieved success using medicines belonging to PDE5 Inhibitors, the most famous of which is Sildenafil (Viagra), but other drugs like Tadalafil are now known to be equally effective, if not better. (The reported success is 25% vs 10% with placebo)
Before you use this medicine, please confirm that your cardiologist or physician is comfortable with your using PDE5 Inhibitors as they can cause trouble in elderly patients with poor cardiac reserve.
There is one more option which is Intermittent androgen deprivation therapy (IAD) where you can actually take a break from Injection of Eligard (under medical supervision of course, and see if erections return). This does not cause a major problem as far of control of prostate cancer is concerned, and select urologists have actually reported that the control of cancer might even be better and this mode actually delays the progression of prostate cancer to an androgen independent stage.
Regards.

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Brief Answer:
Sildenafil / Tadalafil should work

Detailed Answer:
Hi,
If it has indeed been 5 years from the date of your treatment, you can anticipate good results from Sildenafil / tadalafil if your physician is comfortable about your using the medication.
Also at the same time, I would prefer that you also get a few more tests done. These include a Serum Prostate Specific Antigen (P.S.A.), and also a Serum Testosterone ( total) assay, preferably at 8 am.
The reports of these also will help us guide you choose the best way forward.
Regards.

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