Hi Keith. Faced with your dilemma, I would initially approach your wife's GP to see if s/he can advise you. Perhaps they could provide you with a letter (for a fee, probably) to show to a doctor or pharmacist in Tenerife. Also, on my website's page, English Doctors in Tenerife, you'll find email addresses for a selection of doctors or medical centres, so you could contact them to ask what documentation you would require. That's all I can offer, I'm afraid. Good luck!