Addiction to heroin and opium is common and associated with morbidities and mortalities which cause huge costs [1,2]. Heroin and opium have differences in chemistry, pharmacokinetics and pharmacodynamics [3,4]. Heroin (3, 6-diacetylmorphine) is a semisynthetic derivative of morphine and a prodrug [4], and morphine is the main constituent of opium [2]. The effects of opium are primarily due to morphine [2]. As heroin is more lipid-soluble than morphine, its entry into brain is faster than morphine. Heroin is rapidly metabolized to the active metabolites 6-acetylmorphine and morphine in the brain. Heroin has faster onset of action and more severe effects than morphine. The nature and duration of acute heroin and opium withdrawal syndromes are comparable [4]. The acute heroin withdrawal syndrome begins after 4–6 h, peaks on day 3 and lasts for 6–10 days [5]. The acute heroin withdrawal syndrome is more intense than acute opium withdrawal. Thus, data about treatment of opium withdrawal may not apply to heroin [6]. Treatment of opioid addiction has 2 goals: first, treatment of acute withdrawal syndrome or detoxification and second, maintenance treatment [7]. Treatment of acute withdrawal syndrome facilitates abstinence from opioid and retention of patients in treatment programs [7]. Maintenance treatment maintains abstinence and prevents relapse to addiction [7]. Mu-opioid receptor agonists (e.g., methadone), μ-opioid receptor partial agonists (e.g., buprenorphine), and α2-adrenergic receptor agonists (e.g., lofexidine) are the standard drugs used for the treatment of acute heroin withdrawal syndrome [7].

Medicinal plants are one of the modalities of treatment of the opioid withdrawal syndrome [8]. Decoction of the seeds of Sophora alopecuroides var. alopecuroides (S. alopecuroides) is used for the treatment of heroin, opium, methamphetamine and nicotine addiction, and pain and diarrhea in the Iranian folk medicine [9,10]. Also, S. alopecuroides 400 mg extract capsules are manufactured for the treatment of acute opium withdrawal syndrome in Iran. The S. alopecuroides extract was as effective as methadone in suppressing the morphine withdrawal in mice [9]. Also, three 400 mg extract capsules once daily for 8 days safely mitigated the acute opium withdrawal in a randomized controlled trial [10]. However, there has been no research into the effects of S. alopecuroides on the acute heroin withdrawal. Moreover, the efficacy and safety of S. alopecuroides for the treatment of opioid withdrawal needs further research. Therefore, this study was conducted to assess the efficacy and safety of the S. alopecuroides extract in the treatment of the acute heroin withdrawal.