The purpose of this study is to determine whether low-dose ketamine infusion is effective in suppressing the symptoms of opiate withdrawal during rapid opiate antagonist induction (RAI).

Inclusion Criteria:

• Diagnosed opiate dependence according to ICD 10 and/or DSM 4;
• Duration of substance abuse more than 1 year
• No or minor co-morbidities;
• Grade I-II according to physical status classification system of American Society of Anesthesiologists.

Exclusion Criteria:

• Current history of long acting opiate or poly-substance abuse;
• Acute medical or surgical condition;
• Pregnancy;
• Breastfeeding.