Inclusion Criteria:
* Patient hospitalized in rheumatology,
* Patient presenting with acute pain in the musculoskeletal system,
* Expected remaining length of hospital stay ≥ 4 days,
* EN ≥ 3
* Age ≥ 18 and ≤ 75,
* Patient who has read and understood the information letter and signed the consent form
* Women:
* Of childbearing age, defined by the CTCG as fertile women, after menarche and until menopause, except in cases of permanent infertility (including hysterectomy, bilateral salpingectomy, or bilateral oophorectomy)
* using highly effective contraception according to the CTCG (combined hormonal contraception (estrogen and progesterone) associated with ovulation inhibition (oral, intravaginal, transdermal), hormonal contraception (progesterone only) associated with ovulation inhibition (oral, injectable, implantable), intrauterine device, intrauterine hormone-releasing system, bilateral tubal occlusion, vasectomized partner, sexual abstinence) for at least 4 weeks prior to inclusion, during treatment, and up to 3 days after the last dose/administration of treatment,
* and having a negative urinary pregnancy test for β-HCG at inclusion.
* Postmenopausal: Menopause is defined by the CTCG as the absence of menstruation for 12 months without any other medical cause. Elevated follicle-stimulating hormone (FSH) levels in the postmenopausal interval can be used to confirm postmenopausal status in women who are not using hormonal contraception or hormone replacement therapy. However, in the absence of 12 months of amenorrhea, a single FSH measurement is insufficient.
* Patient affiliated with a social security system or beneficiary of such a system.
Exclusion Criteria:
* Patients who have received nefopam within 7 days prior to inclusion
* Patients with creatinine clearance ≤ 30 mL/min according to the CKD-EPI formula
* Severe or uncontrolled cardiovascular disease. Patients treated with enzyme-inducing or enzyme-inhibiting drugs (amiodarone, bupropion, fluoxetine, paroxetine, quinidine, venlafaxine, haloperidol, imipramine, tamoxifen, ketoconazole, ritonavir, clarithromycin, Carbamazepine, St. John's Wort, Itraconazole, Rifampicin, Dexamethasone)
* Patients treated with medication(s) containing alcohol as an excipient.
* Patients with severe hepatic impairment (ASAT and/or ALAT \> 5 times the upper normal limit).
* History of psychological or sensory disease or abnormality that may prevent the subject from fully understanding the conditions required for participation in the protocol or prevent them from giving informed consent.
* Patients unable to understand pain scales.
* Medical contraindications for NEFOPAM VIATRIS 20 mg/2 mL, injectable solution, or NEFOPAM PANPHARMA 30 mg, film-coated tablet:
* Hypersensitivity to nefopam or any of the excipients.
* Convulsions or history of convulsive disorders.
* Risk of urinary retention associated with urethroprostatic disorders.
* Risk of angle-closure glaucoma.
* Patients suffering from constipation.
* Patients with a history of disorders associated with the use of psychoactive substances.
* Pregnant women, women in labor, breastfeeding women, or women who are not using effective contraception.
* Persons deprived of their liberty by administrative or judicial decision or persons placed under judicial protection/guardianship or curatorship
