Pre-inclusion Criteria:

• Males and females ≥ 18 years old

• Patient already in care or newly initiating care in Addictology departments for a beharioural addiction, diagnosed with current:

  • Gambling disorder [NORC DSM Screen for Gambling Problems (NODS), revised for DSM-5]
  • Food addiction [Yale Food Addiction Scale (YFAS), revised for DSM-5]
  • Or Sexual addiction [interview adapted from the NODS to explore the diagnostic criteria proposed by Carnes et al. (2012): NODS-SA]

• Able to regularly assess and report their craving episodes on a weekly diary

• Who provide their written informed consent

• Affiliated with French social security system or beneficiary from such system

• Having presented at least one episode of craving with an intensity ≥ 4/10 at the NRS during the week prior to inclusion

Women must meet one of the following criteria at the time of inclusion:

• use adequate contraceptive measures as recommended by the CTFG (Recommendations related to contraception and pregnancy testing in clinical trials v1.1), and have a negative pregnancy test (urine test) prior to receiving the first dose of study drug;
• or be post-menopausal (over 50 years of age with amenorrhea for at least 12 months after discontinuation of all exogenous hormonal therapy)
• or (if under 50 years of age) have been amenorrheic for at least 12 months after discontinuation of exogenous hormonal therapy and with luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels corresponding to post-menopausal levels
• or have undergone irreversible surgical sterilization by hysterectomy, bilateral oophorectomy or bilateral salpingectomy (this operation must be documented).

• Being currently treated by another anti-craving drug that have been already tested for craving reduction in BAs (naltrexone, acamprosate, baclofène, topiramate, bupropion, N-acetyl-cystéine, disulfiram, etc.);

• Presenting a contraindication for the use of nalmefene (listed in the SmPC):

  • Known hypersensitivity to the active substance or to any of the excipients. In particular, intolerance to galactose or deficiency in Lapp lactase or glucose-galactose malabsorption (rare hereditary diseases);
  • Treatment by opioid agonists (full or partial) (opioid pain relievers, opioid substitution drugs);
  • Recent history of opioid dependence or current opioid dependence;
  • Current symptoms of the acute opioid withdrawal syndrome;
  • Suspected recent consumption of opioid (necessity to consider the half-life);
  • Severe hepatic impairment (Child-Pugh stage B or C);
  • Severe renal impairment (estimated glomerular filtration rate [TFGe] <30 mL/min/1.73 m2);
  • History of recent acute alcohol withdrawal syndrome (including hallucinations, convulsions and delirium tremens).

• Predictable opioid treatment during the study period;

• Unstable psychiatric disorders (meaning disorders for which the treatment was modified since less than a month (corresponding to the instauration of a new treatment, or the increase in dosage of a treatment already being taken)), including severe risk of suicide (i.e. necessity to engage specific medication or hospitalization; psychotropic medication engaged since less than 1 month; absence of improvement after one month of medication) (because nalmefene has not been studied in patients with unstable psychiatric disorders). Patients with a food addiction diagnosed with eating disorders marked by the presence of binge eating can be included;

• Anorexia nervosa-restricting type (because food addiction concept is poorly established among patients with AN-R, who do not have binge eating episodes induced by craving);

• Extreme leanness (body mass index < 16.5) (because loss of appetite and/or weight loss are frequent adverse effects of nalmefene);

• Current treatment with potent inhibitor drugs of the UGT2B7 (UDP-Glucuronosyltransferase-2B7); for example: diclofenac, fluconazole, medroxyprogesterone acetate, meclofenamic acid;

• Current treatment with UGT inducing drugs; for example: dexamethasone, phenobarbital, rifampicin, omeprazole;

• Inability to indicate the time of day of the most intense craving episode (because this information will determine the time of day the treatment should be taken);

• Pregnancy (attested by a pregnancy urinary test for women of childbearing age) or breastfeeding woman;

• Trusteeship;

• Major cognitive impairment;

• Not fluent in French;

• Participation to another interventional study during the last month or expected participation to another interventional study during participation to the NABAB study.