What is the treatment for vitamin D toxicity (Vit D) poisoning?

Treatment of Vitamin D Toxicity (Super D Poisoning)

Immediately discontinue all vitamin D supplementation and aggressively manage hypercalcemia with intravenous saline hydration, loop diuretics, glucocorticoids, calcitonin, and bisphosphonates when calcium exceeds 14 mg/dL. 1

Understanding Vitamin D Toxicity

Diagnostic Criteria:

• Vitamin D toxicity typically occurs at 25(OH)D levels >150 ng/mL (>375 nmol/L), with levels >200 ng/mL (>500 nmol/L) associated with acute toxicity 1, 2
• The upper safety limit for 25(OH)D is 100 ng/mL, above which toxicity risk increases substantially 3
• Hypercalcemia caused by excess vitamin D in generally healthy adults has been observed only if daily intake was >100,000 IU or if the 25(OH)D level exceeded 100 ng/mL 3

Laboratory Findings:

• Hypercalcemia (often >14 mg/dL in severe cases) 2
• Suppressed parathyroid hormone (PTH) 1, 2
• Normal or high serum phosphorus levels 2
• Normal or low alkaline phosphatase (ALP) 2
• High urine calcium/creatinine ratio 2
• Markedly elevated serum 25(OH)D levels (>150 ng/mL) 2

Immediate Management Protocol

Emergency Intervention (Calcium >14 mg/dL):

Emergency intervention is necessary when calcium exceeds 14 mg/dL because of adverse effects on cardiac, central nervous system, renal, and gastrointestinal functions 2. The treatment approach includes:

1. Discontinue all vitamin D sources immediately 1, 2

   • This is the first and most critical step
   • Remember that vitamin D is stored in fat tissues, so effects of toxicity may last for months despite removal of the exogenous source 2

2. Intravenous hydration with saline 1, 2

   • Aggressive IV saline to promote calciuresis
   • This is the cornerstone of acute hypercalcemia management

3. Loop diuretics 1, 2

   • Administer after adequate hydration to enhance calcium excretion
   • Do not give before adequate volume repletion

4. Glucocorticoids 1, 2

   • Particularly effective in vitamin D toxicity as they reduce intestinal calcium absorption
   • Also decrease conversion of 25(OH)D to active 1,25(OH)2D

5. Calcitonin 1, 2

   • For rapid reduction of calcium levels
   • Effect may be transient (tachyphylaxis develops)

6. Bisphosphonates 1, 2

   • For sustained reduction in calcium levels
   • Particularly useful when calcium remains elevated despite other measures

Supportive Measures

Dietary Modifications:

• Institute a low calcium and phosphorus diet 2
• This reduces the substrate for hypercalcemia while other treatments take effect

Expected Clinical Course

Duration of Toxicity:

• Effects may persist for months even after discontinuation due to vitamin D storage in adipose tissue 2, 4
• In documented cases, it took approximately 6 months for renal function and 18 months for vitamin D values to return to normal after stopping a very high dose regimen 4
• Serum calcium typically normalizes within 1 week with appropriate treatment 4

Clinical Manifestations to Monitor

Symptoms of Vitamin D Toxicity:

• Nausea and vomiting 2, 5
• Muscle weakness 4, 5
• Altered sensorium 5
• Constipation 5
• Pancreatitis 5
• Acute kidney injury 4, 5
• Weight loss 5

Critical Pitfalls to Avoid

Common Causes of Toxicity:

• Overzealous correction of vitamin D deficiency with mega-doses is the most common cause in recent reports 5
• Prescription of cumulative doses in the millions of IU (e.g., 3,600,000-6,360,000 IU cumulative) has resulted in toxicity 5
• Medication errors, including both prescribing errors and manufacturing defects, have been documented 4, 6

Important Considerations:

• Not all patients with very high 25(OH)D levels develop symptomatic hypercalcemia, though this is rare 7
• The severity of symptoms correlates with serum calcium concentration and duration of hypercalcemia, not just vitamin D levels 2
• Repeated monitoring is essential during treatment as the stored vitamin D continues to be released from adipose tissue 2, 4

Prevention Strategies

To Prevent Future Cases:

• Always check baseline serum 25(OH)D levels before starting vitamin D therapy 2
• Question patients about previous vitamin D administration before prescribing 2
• Ask parents of infants about dietary or oral supplements, with serial questioning during supplementation 2
• Avoid single very large doses (>300,000 IU) as they may be inefficient or potentially harmful 8
• Daily doses up to 4,000 IU are generally considered safe for adults 3, 8