A RANDOMIZED STUDY TO DETERMINE WHETHER ROUTINE INTRAVENOUS MAGNESIUMSUPPLEMENTS ARE NECESSARY IN PATIENTS RECEIVING CISPLATIN CHEMOTHERAPY WITH CONTINUOUS-INFUSION 5-FLUOROURACIL

Cisplatin is an effective antineoplastic agent, but can cause renal tu bular damage leading to urinary magnesium wasting and hypomagnesaemia. Cisplatin and 5-fluorouracil, when used in combination, have synergis tic antitumour activity in upper gastrointestinal malignancies, but it is unclear whether they have additive effects on renal magnesium loss . To determine the optimal regimen for magnesium supplementation in th ese patients, we have conducted a randomised trial of routine intraven ous magnesium supplements compared with magnesium given on an 'as requ ired' basis. 32 patients were randomised to receive magnesium intraven ously in prehydration and posthydration fluids with cisplatin chemothe rapy, or to receive magnesium only when the serum level was low. 5-flu orouracil was given as a continuous infusion. Serum magnesium was meas ured on admission for each cycle of chemotherapy and an interim measur ement performed between each cycle. 28 patients were evaluable. All pa tients randomised to receive magnesium on an 'as required' basis had a t least one episode of hypomagnesaemia. On subsequent admissions for c hemotherapy (cycles 2 and 3), the mean serum magnesium level was signi ficantly lower in these patients compared with patients who received m agnesium routinely (P < 0.05). After omission of magnesium from the fi rst cycle of cisplatin, magnesium supplements were necessary in 50% of subsequent cycles, usually by the second or third cycle. Moreover, th ere were several instances of symptomatic hypomagnesaemia requiring fu rther intravenous supplements in mid-cycle. Patients treated with a co mbination of cisplatin and 5-fluorouracil should be given intravenous magnesium supplements with each cycle of cisplatin chemotherapy. Never theless, episodes of hypomagnesaemia still occur, and additional intra venous supplements may be required, highlighting the importance of mea suring this electrolyte.