FENTANYL is flooding Malaga prisons, authorities warn, as reports grow of inmates receiving the deadly drug in their mail. Officials say the powerful opioid, dubbed the ‘zombie drug,’ has been turning up in letters and patches sent to prisoners – sometimes even from their own families. TAMPM added the incident highlighted how easy it has become to slip tiny, hard-to-spot patches through the postal system. Authorities say they are stepping up checks on correspondence – but admit the tiny patches are extremely difficult to detect. Fentanyl is a synthetic opioid that is 50 to 100 times more powerful than morphine.