Opioid use disorder (OUD) is a health crisis in Canada and around the world. OUD is characterized by a dependency on opioid drugs and/or prescription opioid medications, and people living with OUD experience a euphoria commonly known as “getting high.” People of all ages and/or sociodemographic backgrounds can develop OUD; however, known risk factors include younger age (i.e., adolescents and young adults), a history of substance abuse, and/or comorbid mental illness. People living with OUD often experience significant morbidity and mortality, including loss of livelihood and/or social networks and supports, homelessness, increased hospitalization, and death. Increasingly, the opioid crisis is being driven by the misuse of opioid medications that are commonly prescribed for patients experiencing pain — in particular, chronic pain. Treatment for OUD is generally multi-modal, including both behavioural and pharmacological interventions. Opioid agonist therapy (OAT) and methadone maintenance therapy (MMT) are effective medical interventions for reducing the symptoms of dependency and supporting patients with OUD to reduce and abstain from their misuse of opioids. OAT and MMT medications include methadone and buprenorphine, which are longer-acting opioid medications as compared to the shorter-acting opioid drugs and medications that can cause OUD. OAT and MMT thereby reduce the symptoms of withdrawal without producing the effect of getting high. However, like all opioid medications and drugs, OAT and MMT cause side effects, such as constipation and sexual dysfunction (including erectile dysfunction [ED] in men). These side effects can cause discomfort and distress, and may discourage patients undergoing OAT or MMT from continuing with treatment, which can increase the risk of relapse. Constipation has been described as a common and persistent side effect of OAT and MMT. Opioid-induced constipation is a side effect common to all opioid drugs and medications, and is described as one of the most common gastrointestinal adverse effects caused by this class of drugs. In addition to more serious complications from chronic constipation, it can cause bloating, discomfort, and reduced quality of life for affected patients. Common treatments for constipation include dietary and lifestyle interventions (such as increased fibre and/or exercise) and/or laxatives (including stimulants, stool softeners, and fibre supplements). Although there is some information and evidence to inform the treatment of opioid-induced constipation in patients receiving prescribed opioids, less information is known to be available to inform best practices for treating OUD patients with constipation as a side effect of OAT or MMT. Sexual dysfunction is also a side effect of opioid drugs and medications — including OAT and MMT — and can occur in both men and women. Sexual dysfunction causes a variety of deleterious symptoms, including abnormalities in sexual desire, arousal, and satisfaction, and sometimes resulting in ED for men. Sexual dysfunction and/or ED may have various underlying causes, including those of a physiologic, social, and/or psychological etiology. The association between exposure to OAT and sexual dysfunction (including ED) is well-established. Treatments for ED in the general population may include medical, mechanical, and/or surgical interventions; however, less information is known to be available to inform best practices for the treatment of ED as a side effect of OAT or MMT in patients living with OUD. Given the benefits that OAT and MMT can offer to patients living with OUD — as well as the known side effects of these medications and the limited information available to inform treatment to reduce their deleterious effects — there is a need to assemble and assess available evidence addressing this topic. Thus, the purpose of this report is to identify and summarize evidence and guidelines describing the clinical effectiveness and/ or recommendations to inform the use of laxatives and/or ED medication for OUD patients undergoing OAT or MMT.