Does 9 days 20mg intake of famotidine cause persistant erectyle disfunction?

Doubtful. Erectile dysfunction (ed) is a rarely reported side effect of famotidine. If you have discontinued the medication and still have ed, a visit to your md will help to elucidate other more likely causes, like if you are taking a beta blocker or an ace inhibitor for hypertension, or an antidepressant.