Magnesium depletion in patients receiving cisplatin-based chemotherapy.

AIMS: To assess the incidence of hypomagnesaemia, the influence of different cisplatin dosages on the degree of hypomagnesaemia and the effect of routine magnesium supplementation on magnesium levels.

MATERIALS AND

METHODS

Magnesium levels for 214 consecutive patients receiving cisplatin-based chemotherapy were studied. Twenty different chemotherapy regimens were prescribed. Doses ranged from 7 to 51 mg/m(2)/week. The interval between cycles ranged from 1 to 4 weeks. The number of evaluable cycles ranged from one to eight. Patients receiving bleomycin, etoposide and cisplatin (BEP) chemotherapy routinely received 60 mmol magnesium per cycle; patients receiving cisplatin, vincristine, methotrexate, bleomycin - dactinomycin, cyclophosphamide, etoposide (POMB-ACE) chemotherapy routinely received 20 mmol magnesium per cycle. For all other chemotherapy regimens, magnesium was not routinely prescribed.

RESULTS

Baseline magnesium levels were available for 195 patients, 92% were within the normal range. The average level was 0.82 mmol/l. There was a statistically significant decrease in magnesium levels from baseline to the lowest magnesium level (mean = 0.68 mmol/l, standard deviation = 0.13) (P < 0.0005). The incidence of hypomagnesaemia (serum magnesium < 0.7 mmol/l) at any point during chemotherapy was 43%. Multiple regression analysis showed a significant association between dose, frequency, and number of cycles given, and the degree of hypomagnesaemia (P = 0.001, P = 0.03 and P < 0.0005, respectively). Routine magnesium supplementation significantly reduced the degree of hypomagnesaemia if sufficient amounts of magnesium are given: 60 mmol magnesium per cycle for a regimen containing 33 mg/m(2)/week cisplatin is sufficient; 20 mmol magnesium per cycle for a regimen containing 40 mg/m(2)/week cisplatin is insufficient.

CONCLUSIONS

It is recommended that magnesium levels should be measured routinely in all patients receiving cisplatin and that all cisplatin-based chemotherapy regimens should be supplemented routinely with sufficient doses of magnesium (40-80 mmol magnesium per cycle depending on the regimen).