DRUG INTERACTIONS
Drug Interactions:
A possible drug interaction of foscarnet sodium and intravenous pentamidine has been described. Concomitant treatment of four patients in the United Kingdom with foscarnet sodium and intravenous pentamidine may have caused hypocalcemia; one patient died with severe hypocalcemia. Toxicity associated with concomitant use of aerosolized pentamidine has not been reported.
Since foscarnet decreases serum concentrations of ionized calcium, concurrent treatment with other drugs known to influence serum calcium concentrations should be used with particular caution. Fatalities have been reported in post-marketing surveillance during concomitant therapy with foscarnet and pentamidine.
Because of foscarnet’s tendency to cause renal impairment, the use of foscarnet sodium should be avoided in combination with potentially nephrotoxic drugs such as aminoglycosides, amphotericin B and intravenous pentamidine (see above) unless the potential benefits outweigh the risks to the patient.
Abnormal renal function has been observed in clinical practice during the use of foscarnet sodium and ritonavir, or foscarnet sodium, ritonavir, and saquinavir. (See
DOSAGE AND ADMINISTRATION
).
Ganciclovir:
The pharmacokinetics of foscarnet and ganciclovir were not altered in 13 patients receiving either concomitant therapy or daily alternating therapy for maintenance of CMV disease.
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