• SOWS-Gossop score on Day 3 during the treatment phase & time-to-dropout for the subjects in the two treatment groups. during the treatment phase. [ Time Frame: Day 3 of treatment phase for the SOWs score. Time to dropout will be measured as the number of 6-hour time quadrants until a subject withdraws or completes the treatment phase of the study ] [ Designated as safety issue: No ]
  

Inclusion Criteria:

Potential subjects must:

1. Be at least 18 years of age.
2. Have current dependence, according to SCID criteria, on any opioid with a half-life similar to heroin or morphine, including Vicodin, Lortab, or Lorcet, Percocet, Percodan, Tylox, or Hydrocodone (by any route of administration), or oxycodone (oxycodone and oxycodone time-released formulation when crushed and snorted, injected or swallowed after chewing).
3. Be seeking treatment for opiate dependence.
4. Have a score greater than or equal to 2 on the Objective Opiate Withdrawal Scale-Handelsman (OOWS) immediately prior to admission.
5. Have reported use of heroin, morphine, or any opioid with a half-life similar to heroin or morphine, for at least 21 of the past 30 days.
6. Have urine toxicology screen positive for opiates and negative for methadone or buprenorphine.

7. If female and of child bearing potential, agree to use of one of the following methods of birth control:

   1. oral contraceptives
   2. patch
   3. barrier (diaphragm, sponge or condom) plus spermicidal preparations
   4. intrauterine contraceptive system
   5. levonorgestrel implant
   6. medroxyprogesterone acetate contraceptive injection
   7. complete abstinence from sexual intercourse
   8. hormonal vaginal contraceptive ring
   9. surgical sterilization or partner sterile (must have documented proof)
8. Have completed the ASI during screening and all other assessments (SOWS-Gossop OOWS, and MCGI) during the baseline period.
9. Be able to verbalize understanding of the consent form, able to provide written informed consent, verbalize willingness to complete study procedures and pass the study consent quiz with 100% accuracy (if necessary, quiz may be administered more than one time).

Exclusion Criteria:

Potential subjects must not:

1. Be female subjects who are pregnant or lactating.
2. Have self-reported use of methadone or buprenorphine in the past 14 days.

3. Have serious medical illnesses including, but not limited to:

   1. Seizures, or those who have received anticonvulsant therapy during the past 5 years.
   2. Pancreatic disease such as insulin-dependent diabetes.
   3. Liver disease requiring medication or medical treatment, and/or aspartate or alanine aminotransferase levels greater than 5 times the upper limit of normal.
   4. Gastrointestinal or renal disease, which would significantly impair absorption, metabolism or excretion of study drug, or would require medication or medical treatment.
4. Have a psychiatric disorder, as assessed by the SCID, including but not limited to dementia or any disorder that, in the opinion of the study physician requires ongoing treatment that would make study participation unsafe or which would make treatment compliance difficult.
5. Have self-reported AIDS.

6. Have an abnormal cardiovascular exam prior to randomization, including any of the following:

   1. Clinically significant abnormal ECG (e.g., second or third degree heart block, uncontrolled arrhythmia, or QTc interval > 450 msec for males, and > 470 msec for females).
   2. Heart rate less than 45 bpm or symptomatic bradycardia.
   3. Systolic blood pressure < 90 mm Hg or symptomatic hypotension (diastolic blood pressure < 60 mm Hg).
   4. Blood pressure > 160/100 mm Hg.
   5. Prior history of myocardial infarction.
7. Have clinically significant abnormal laboratory values.
8. Require any of the following medications currently or within the past 4 weeks: psychotropics (including sedatives/hypnotics, antidepressants, neuroleptics), prescription analgesics (excluding those listed in inclusion criteria #2 above), anticonvulsants, antihypertensives, antiarrhythmics, antiretroviral, and cholesterol lowering medications. Nicotine replacement therapy (patch, inhaler, gum, or nasal spray) for nicotine-dependent subjects are allowed.
9. Have current dependence (by SCID criteria) on any psy