Pain relief study halted: did d-cycloserine fail for back pain?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Must have a history of low back pain for a minimum of 6 months with or without signs and symptoms of radiculopathy * Male or female, age 18 years or older, (no racial/ethnic restrictions) * Must have an average pain score of ≥ 4 (on a 0-10 NRS) over a 5-7 day period (minimum of daily eDiary entries for at least 5 of 7 days) immediately preceding the baseline visit (visit 2) * Must be willing to read and able to understand instructions as well as patient reported outcomes (PROs) * Must be in generally stable health * Must sign an informed consent document after complete explanation of the study documenting that they understand the purpose of the study, procedures to be undertaken, possible benefits, potential risks, and are willing to participate * Must be willing to discontinue all pain medications for chronic back pain (listed below) except the study medication and rescue medication provided and not use the following prohibited pain medications throughout the duration of the treatment period * analgesics including over the counter (OTC) medications * NSAIDS including OTC medications * Coxibs * Opioids * Muscle relaxants * Gabapentins including pregabalin and gabapentin * Must be willing to comply with recording pain, mood, and study treatment adherence twice daily using study eDiary * Must be willing to abstain from drinking alcohol during the course of the study. * If female, must be post-menopausal for at least one year or practicing an accepted, highly effective method of contraception or abstinence and plan to continue during the course of the study. Exclusion Criteria: * Low back pain associated with any systemic signs or symptoms, e.g., fever, chills * Evidence of rheumatoid arthritis, ankylosing spondylitis, acute vertebral fractures, fibromyalgia, or history of surgery or tumor in the back within the past 6 months * Involvement in litigation regarding their back pain or has a disability claim or is receiving workman's compensation or is seeking either as a result of their low back pain * Epidural steroid injection within the past 3 months * History of seizures * Major new or untreated psychiatric disorder during the past 6 months and/or ongoing treatment with buproprion or fluphenazine * Beck Depression Inventory II score of \>28 * Significant renal disease or severe renal insufficiency * Substance abuse/dependence including alcohol within the past 6 months * Significantly abnormal laboratory values * Pregnant or lactating at the time of randomization * Known sensitivity to D-cycloserine * Currently taking any of the following medications: ethionamide, dilantin, isoniazid (INH) * In the judgment of the investigator, unable or unwilling to follow the protocol and instructions * Any change in medication or physical therapy regime for back pain in the last 30 days. * Chronic progressive neurologic conditions, including Parkinson's disease, Alzheimer's disease, and other conditions associated with dementia * Other medical disease such as clinically significant congestive heart failure, coronary or peripheral vascular disease, chronic obstructive lung disease, or malignancy * Presence of undiagnosed skin lesions or history of melanoma * Current use of recreational drugs * Current use of medical marijuana * High dose opioid prophylaxis, defined as \> 50mg morphine equivalent/day * Intra-axial implants (e.g. spinal cord stimulators or pumps) * Pregnancy or inability to use an effective method of birth control in sexually active men and women while taking the study drug and for one week thereafter. Barrier contraceptives (condoms or diaphragm) with spermicide, intrauterine devices (IUD's), hormonal contraceptives, oral contraceptive pills, surgical sterilization, and complete abstinence are examples of effective methods of contraception. * Following laboratory abnormalities: liver function tests (SGOT/SGPT) greater than 2.5 times the upper limit of normal; unexplained anemia; evidence of renal insufficiency (creatinine \> upper limit of normal) or any other abnormality that the principal investigator feels puts the participant at risk during the study. * Any medical condition that in the investigator's judgment may prevent the individual from completing the study or put the individual at undue risk * Lactose allergy * Ongoing participation in another clinical research study involving an investigational product or having received another investigational product within the last 90 days