Drug Interactions between milnacipran and Vitamin D3

MONITOR: Additive effects and possible toxicity (e.g., hypercalcemia, hypercalciuria, and/or hyperphosphatemia) may occur when patients using vitamin D and/or vitamin D analogs ingest a diet high in vitamin D, calcium, and/or phosphorus. The biologically active forms of vitamin D stimulate intestinal absorption of calcium and phosphorus. This may be helpful in patients with hypocalcemia and/or hypophosphatemia. However, sudden increases in calcium or phosphorus consumption due to dietary changes could precipitate hypercalcemia and/or hyperphosphatemia. Patients with certain disease states, such as impaired renal function, may be more susceptible to toxic side effects like ectopic calcification. On the other hand, if dietary calcium is inadequate for the body's needs, the active form of vitamin D will stimulate osteoclasts to pull calcium from the bones. This may be detrimental in a patient with reduced bone density.

MANAGEMENT: Given the narrow therapeutic index of vitamin D and vitamin D analogs, the amounts of calcium, phosphorus, and vitamin D present in the patient's diet may need to be taken into consideration. Specific dietary guidance should be discussed with the patient and regular lab work should be monitored as indicated. Calcium, phosphorus, and vitamin D levels should be kept within the desired ranges, which may differ depending on the patient's condition. Patients should also be counseled on the signs and symptoms of hypervitaminosis D, hypercalcemia, and/or hyperphosphatemia.

GENERALLY AVOID: Use of milnacipran in conjunction with chronic alcohol consumption may potentiate the risk of liver injury. Milnacipran alone can increase serum transaminase levels. In placebo-controlled fibromyalgia trials, increases in ALT were more frequently observed in patients treated with milnacipran 100 mg/day (6%) and 200 mg/day (7%) compared to patients treated with placebo (3%). One patient receiving milnacipran 100 mg/day (0.2%) had an increase in ALT greater than 5 times the upper limit of normal (ULN) but did not exceed 10 times the ULN. Increases in AST were also more frequently observed in patients treated with milnacipran 100 mg/day (3%) and 200 mg/day (5%) than in patients treated with placebo (2%). There have been reported cases of increased liver enzymes and severe liver injury, including fulminant hepatitis, from foreign postmarketing experience with milnacipran. Significant underlying clinical conditions and/or use of multiple concomitant medications were present in the cases of severe liver injury.

MANAGEMENT: Due to the risk of liver injury, patients prescribed milnacipran should be counseled to avoid excessive use of alcohol. Milnacipran should generally not be prescribed to patients with substantial alcohol use.