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).