Vitamin D as a Therapeutic Adjunct in the Stimulant Treatment of ADHD

Inclusion Criteria

• Age 18-50 years
• Voluntary, written, informed consent
• Physically healthy by medical history, physical, neurological, ECG, and laboratory examinations
• For females, non-lactating, with a negative serum or urine pregnancy test
• Lab results without clinically relevant findings (e.g. renal function, electrolytes, and vitamin D levels)
• English speaking

Exclusion Criteria

• Medical contraindication to Dexedrine administration (e.g., history of cardiac problems, seizures, glaucoma, hypertension, hyperthyroidism, etc.)
• Medical contraindication to calcitriol administration (e.g., history of hypersensitivity to calcitriol or any component of the formulation, hypercalcemia or vitamin D toxicity)
• History of substance dependence (e.g., alcohol, opiates, sedative hypnotics), except for nicotine
• A primary major DSM-5 psychiatric disorder (e.g., schizophrenia, bipolar disorder, major depression, etc.) as determined by the Structured Clinical Interview for DSM-5 (SCID)
• A history of significant medical (e.g., cardiovascular, diabetic/metabolic) or neurological (e.g., cerebrovascular accidents, seizure, traumatic brain injury) illness
• Positive answers on the cardiac history questionnaire that may place the subject at higher risk, as determined by an internal medicine specialist or cardiologist's review of both the questionnaire responses and screening ECG
• Current use of psychotropic and/or potentially psychoactive prescription medications
• For females, laboratory (β-HCG) or physical evidence of pregnancy/lactation 9) MRI-incompatible implants and other contraindications for MRI (i.e., aneurysm clip, metal fragments, internal electrical devices such as a cochlear implant, spinal cord stimulator or pacemaker)
• History of claustrophobia or feeling of inability to lie still on his/her back for the PET or MRI scans
• History of any bleeding disorder or current anticoagulant therapy
• Donation or loss of 550 mL of blood or more (including plasmapheresis) or receipt of a transfusion of any blood product within 8 weeks prior to the first test day.
• Use of any prescription medications and/or over-the-counter medications, vitamins and/or herbal supplements which could have a negative clinical interaction with calcitriol/Dexedrine or which could confound scientific results of the study, within 2 weeks prior to each test day (e.g., thiazide diuretics, Mg based antiacids, digoxin, etc,.).
• Serum levels of 25(OH)D3 below 20 ng/ml.
• Obesity i.e. BMI over 30 (more prone to lower vitamin D levels)
• Subjects with history of prior radiation exposure for research purposes within the past year such that participation in this study would place them over Radioactive Drug Research Committee (RDRC) limits for annual radiation exposure. This guideline is an effective dose of 5 rem received per year.
• Subjects with current, past or anticipated exposure to radiation in the work place
• History of kidney stones within the past 5 years
• Any degree of renal failure
• History of parathyroid disorder (hyper or hypoparathyroidism)
• History of osteoporosis or any pathologic fractures
• Vitamin D supplementation in any form in the past 3 months
• Known hypersensitivity to Dexedrine, [11C]PHNO, or calcitriol
• Malabsorption syndromes (i.e. Celiac sprue)
• Serum corrected calcium > 10.5 mg/dl or phosphate > 4.2 mg/dl