"Infants exposed in the womb to a drug used to treat HIV and reduce the transmission of HIV from mother to child, may have lower bone mineral content than those exposed to other anti-HIV drugs, according to a National Institutes of Health study"...
THE MAJOR TOXICITY OF FOSCAVIR IS RENAL IMPAIRMENT (see WARNINGS section). Approximately 33% of 189 patients with AIDS and CMV retinitis who received FOSCAVIR (60 mg/kg TID), without adequate hydration, developed significant impairment of renal function (serum creatinine > 2.0 mg/dL). The incidence of renal impairment in subsequent clinical trials in which 1000 mL of normal saline or 5% dextrose solution was given with each infusion of FOSCAVIR was 12% (34/280).
FOSCAVIR has been associated with changes in serum electrolytes including hypocalcemia (15-30%), hypophosphatemia (8-26%) and hyperphosphatemia (6%), hypomagnesemia (15-30%), and hypokalemia (16-48%) (see WARNINGS section). The higher percentages were derived from those patients receiving hydration.
FOSCAVIR treatment was associated with seizures in 18/189 (10%) AIDS patients in the initial five controlled studies (see WARNINGS section). Risk factors associated with seizures included impaired baseline renal function, low total serum calcium, and underlying CNS conditions predisposing the patient to seizures. The rate of seizures did not increase with duration of treatment. Three cases were associated with overdoses of FOSCAVIR (see OVERDOSAGE section).
In five controlled U.S. clinical trials the most frequently reported adverse events in patients with AIDS and CMV retinitis are shown In Table 5. These figures were calculated without reference to drug relationship or severity.
TABLE 5 : Adverse Events Reported in Five Controlled
US Clinical Trials
|n = 189||n = 189|
|Fever||65%||Abnormal Renal Function||27%|
From the same controlled studies, adverse events categorized by investigator as “severe” are shown in Table 6. Although death was specifically attributed to FOSCAVIR in only one case, other complications of FOSCAVIR (i.e., renal impairment, electrolyte abnormalities, and seizures) may have contributed to patient deaths (see WARNINGS section).
TABLE 6 : Severe Adverse Events
|n = 189|
|Abnormal Renal Function||14%|
From the five initial U.S. controlled trials of FOSCAVIR, the following list of adverse events has been compiled regardless of causal relationship to FOSCAVIR. Evaluation of these reports was difficult because of the diverse manifestations of the underlying disease and because most patients received numerous concomitant medications.
Incidence Of 5% Or Greater
Gastrointestinal System: anorexia, nausea, diarrhea, vomiting, abdominal pain
Metabolic and Nutritional: mineral and electrolyte imbalances (see WARNINGS) including hypokalemia, hypocalcemia, hypomagnesemia, hypophosphatemia, hyperphosphatemia
Psychiatric: depression, confusion, anxiety
Respiratory System: coughing, dyspnea
Skin and Appendages: rash, increased sweating
Urinary: alterations in renal function including increased serum creatinine, decreased creatinine clearance, and abnormal renal function (see WARNINGS)
Special Senses: vision abnormalities
Incidence Between 1% And 5%
Cardiovascular: hypertension, palpitations, ECG abnormalities including sinus tachycardia, first degree AV block and non-specific ST-T segment changes, hypotension, flushing, cerebrovascular disorder (see WARNINGS)
Central and Peripheral Nervous System: tremor, ataxia, dementia, stupor, generalized spasms, sensory disturbances, meningitis, aphasia, abnormal coordination, leg cramps, EEG abnormalities (see WARNINGS)
Special Senses: taste perversions, eye abnormalities, eye pain, conjunctivitis
Selected adverse events occurring at a rate of less than 1% in the five initial U.S. controlled clinical trials of FOSCAVIR include: syndrome of inappropriate antidiuretic hormone secretion, pancytopenia, hematuria, dehydration, hypoproteinemia, increases in amylase and creatinine phosphokinase, cardiac arrest, coma, and other cardiovascular and neurologic complications.
Selected adverse event data from the Foscarnet vs. Ganciclovir CMV Retinitis Trial (FGCRT), performed by the Studies of the Ocular Complications of AIDS (SOCA) Research Group, are shown in Table 7 (see Clinical Trials section).
TABLE 7: FGRCT: Selected Adverse Events*
|No.of Events||No.of Patients||Rates†||No.of Events||No.of Patients||Rates†|
|Absolute neutrophil count decreasing to <0.50 x 109 per liter||63||41||1.30||31||17||0.72|
|Serum creatinine increasing to >260 pmol per liter (>2.9 mg/dL)||6||4||0.12||13||9||0.30|
|* Values for the treatment groups refer only to patients
who completed at least one followup visit - i.e., 133 to 119 patients in the
ganciclovir group and 93 to 100 in the foscarnet group. “Events” denotes all
events observed and “patients” the number of patients with one or more of the
†Per person-year at risk
‡Final frozen SOCA I database dated October 1991
Selected adverse events from ACTG Study 228 (CRRT) comparing combination therapy with FOSCAVIR or ganciclovir monotherapy are shown in Table 8. The most common reason for a treatment change in patients assigned to either FOSCAVIR or ganciclovir was retinitis progression. The most frequent reason for a treatment change in the combination treatment group was toxicity.
TABLE 8: CRRT: Selected Adverse Events
|No. Events||No. Pts.*||Rate†||No. Events||No. Pts.*||Rate†||No. Events||No. Pts.*||Rate†|
|Anemia (Hgb <70g/L)||11||7||0.20||9||7||0.14||19||15||0.33|
|Neutropenia‡ ANC <0.75 x 109 cells/L||86||32||1.53||95||41||1.51||107||51||1.91|
|ANC <0.50 x 109 cells/L||50||25||0.91||49||28||0.80||50||28||0.85|
|Thrombo- cytopenia Platelets||28||14||0.50||19||8||0.43||40||15||0.56|
|<50 x 109/L Platelets||1||1||0.01||6||2||0.05||7||6||0.18|
|<20 x 109/L Nephrotoxicity Creatinine >260 pmol/L (>2.9 mg/dL)||9||7||0.15||10||7||0.17||11||10||0.20|
|*Pts. = patients with event; †Rate = events/person/year; JANC = absolute neutrophil count|
Adverse events that have been reported in post-marketing surveillance include: ventricular arrhythmia, prolongation of QT interval, gamma GT increased, diabetes insipidus (usually nephrogenic), renal calculus, and muscle disorders including myopathy, myositis, muscle weakness and rare cases of rhabdomyolysis. Cases of vesiculobullous eruptions including erythema multiforme, toxic epidermal necrolysis, and Stevens- Johnson Syndrome have been reported. In most cases, patients were taking other medications that have been associated with toxic epidermal necrolysis or Stevens-Johnson Syndrome.
Read the Foscavir (foscarnet sodium injection) Side Effects Center for a complete guide to possible side effects
A possible drug interaction of FOSCAVIR and intravenous pentamidine has been described. Concomitant treatment of four patients in the United Kingdom with FOSCAVIR 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 FOSCAVIR 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 FOSCAVIR and Pentamidine.
Because of foscarnet's tendency to cause renal impairment, the use of FOSCAVIR 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 FOSCAVIR and ritonavir, or FOSCAVIR, ritonavir, and saquinavir. (See DOSAGE AND ADMINISTRATION.)
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.
Read the Foscavir Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 7/13/2016
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