How often should we keep reviving overdosed drug addicts?

Six times Nikki Dixon has been saved from likely death by heroin overdose because quick-acting friends and emergency responders used the drug antidote naloxone to revive her. But all she remembers is waking up feeling each time like she had the worst possible case of the flu - cold sweats, vomiting, stomach in knots and everything smelling repulsive - and craving another fix to take away the pain of drug withdrawal.