Antiviral therapy
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The time course and magnitude of foscarnet-induced changes in plasma concentrations of total and ionized calcium and magnesium were investigated in 13 male HIV-positive patients who had no active cytomegalovirus-associated disease. The patients had a mean age of 36 years (range 25-49 years) and a mean CD4 cell count of 550 cells/mm3 (range 130-1280 cells/mm3). Peak (mean +/- SD) plasma concentrations of foscarnet (0.89+/-0.10 mmol/l) were seen at the end of the period of drug infusion (90 mg/kg of foscarnet was infused over 2 hours) and declined with a terminal half-life of 5.7+/-0.7 hours. ⋯ In summary, we found that foscarnet-induced changes in the plasma concentrations of total calcium and magnesium were dissociated from the corresponding changes in ionized calcium and magnesium. The maximal decreases in the plasma concentrations of total calcium and magnesium were smaller in magnitude and occurred much later than did the changes in ionized calcium and magnesium. The relative changes in the plasma concentration of ionized magnesium were greater than those of ionized calcium, indicating that foscarnet binds preferentially to the magnesium ion.