Inclusion Criteria:  Age 30-55 years Voluntary, written, informed consent Physically healthy by medical history, physical, neurological, ECG and laboratory examinations DSM-5 criteria for at least moderate Cocaine Use Disorder Recent street cocaine use in excess of quantities used in the current study Intravenous and/or smoked (crack/ freebase) use Positive urine toxicology screen for cocaine Laboratory evidence of vitamin D sufficiency (i.e., 25(OH)-vitamin D3 level ≥ 20/mg) For females, a negative serum pregnancy (HCG) test at screening and admission, and a negative urine pregnancy test (HCG) on cocaine administration days.  Exclusion Criteria:  A history of other substance dependence (except for nicotine). Positive urine toxicology for cannabis is accepted for the study unless there is evidence for dependence per Structured Clinical Interview for DSM-5 (SCID) interview. Positive urine toxicology for other drugs at screening will be repeated. If positive again and/or positive at admission, subjects will be excluded < 1 year of cocaine abuse/dependence A primary DSM-5 Axis I major psychiatric disorder (e.g., schizophrenia, bipolar disorder, major depression, etc.) unrelated to cocaine as determined by the SCID-5 Medical comorbidities including serum calcium ( > 10.5 mg/dl, serum phosphorus > 4.2 mg/dl), hyperparathyroidism, kidney disease (e.g., Serum creatinine > 1.3 mg/dl) A history of significant and uncontrolled medical (e.g., cardiovascular, diabetic/metabolic) or neurological (e.g., cerebrovascular, seizures, traumatic brain injury) illness A history of seizures Current use of psychotropic/potentially psychoactive medications or medications that can have drug drug interactions with calcitriol, including over the counter Vitamin D products, thiazide diuretics, and calcium supplements, etc, as referenced in the package insert for calcitriol Seeking treatment for drug abuse/dependence Hypersensitivity to calcitriol For females, physical or laboratory (HCG) evidence of pregnancy.