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Foscavir Side Effects

Generic Name: foscarnet

Note: This page contains information about the side effects of foscarnet. Some of the dosage forms included on this document may not apply to the brand name Foscavir.

For the Consumer

Applies to foscarnet: intravenous solution

In addition to its needed effects, some unwanted effects may be caused by foscarnet (the active ingredient contained in Foscavir). In the event that any of these side effects do occur, they may require medical attention.

If any of the following side effects occur while taking foscarnet, check with your doctor or nurse immediately:

More common:
  • Increased or decreased frequency of urination or amount of urine
  • increased thirst
Less common:
  • Chills
  • convulsions
  • fever
  • muscle twitching
  • pain at place of injection
  • pain or numbness in hands or feet
  • tingling sensation around the mouth
  • tremor
  • unusual tiredness and weakness
  • Sores or ulcers on the mouth or throat, penis, or vulva

Minor Side Effects

Some of the side effects that can occur with foscarnet may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common:
  • Abdominal or stomach pain
  • anxious feeling
  • confusion
  • dizziness
  • headache
  • loss of appetite
  • nausea and vomiting
  • unusual tiredness or weakness

For Healthcare Professionals

Applies to foscarnet: intravenous solution


Renal impairment was the major toxicity of this drug. The most frequent side effects reported during clinical trials included fever, nausea, anemia, diarrhea, abnormal renal function, vomiting, headache, and seizures. Severe side effects included death, abnormal renal function, bone marrow suppression, anemia, and seizures.[Ref]


Very common (10% or more): Renal impairment (up to 33%), abnormal renal function (up to 27%), increased serum creatinine
Common (1% to 10%): Altered renal function, decreased CrCl, increased BUN, acute renal failure, renal pain
Uncommon (0.1% to 1%): Renal tubular disorder
Frequency not reported: Increased serum creatinine to greater than 2.9 mg/dL, acute tubular necrosis, drug crystals in renal tubules and capillaries, nephrotoxicity
Postmarketing reports: Nephrogenic diabetes insipidus, renal tubular acidosis, renal calculus, renal tubular necrosis, crystal-induced nephropathy[Ref]

About 33% of AIDS patients with CMV retinitis who used this drug without adequate hydration reported significant renal impairment (serum creatinine at least 2 mg/dL). When administered with 1000 mL of normal saline or 5% dextrose solution, the incidence decreased to 12%.

Renal side effects were due to acute tubular necrosis, possibly from deposition of drug crystals in the renal tubules and capillaries. The development of nephrotoxicity was most common during the third week of therapy in 1 study.

Nephrotoxicity was reversible in patients with previously adequate renal function. Hydration with 2.5 liters of normal saline per day beginning the day before therapy decreased the incidence of nephrotoxicity.[Ref]


Very common (10% or more): Serum electrolyte changes, mineral and electrolyte imbalances, hypokalemia (up to 48%), hypocalcemia (up to 30%), hypomagnesemia (up to 30%), hypophosphatemia (up to 26%), decreased appetite, anorexia
Common (1% to 10%): Hyperphosphatemia, abnormal albumin to globulin ratio, hyponatremia, decreased weight, increased alkaline phosphatase, increased lactate dehydrogenase, acidosis, cachexia, thirst
Uncommon (0.1% to 1%): Dehydration, hypoproteinemia
Frequency not reported: Hypercalcemia., decreased serum ionized calcium levels[Ref]

The higher percentages of serum electrolyte changes (including hypokalemia, hypocalcemia, hypomagnesemia, hypophosphatemia, hyperphosphatemia) were reported in patients receiving hydration.

Serum ionized calcium levels have been shown to decrease acutely in a dose-dependent manner after an infusion of this drug. Total calcium and phosphate levels were not significantly affected. This drug is believed to complex with ionized calcium.

More severe metabolic abnormalities have resulted in tremors, twitches, arrhythmias, paresthesias, and seizures.[Ref]


Very common (10% or more): Nausea (up to 47%), diarrhea (up to 30%), vomiting (up to 26%)
Common (1% to 10%): Abdominal pain, constipation, dysphagia, dyspepsia, rectal hemorrhage, dry mouth, melena, flatulence, ulcerative stomatitis, pancreatitis
Uncommon (0.1% to 1%): Increased amylase
Frequency not reported: Uvula ulceration
Postmarketing reports: Esophageal ulceration[Ref]


In controlled trials, death was specifically attributed to this drug in 1 case; however, other drug complications (e.g., renal impairment, electrolyte abnormalities, seizures) may have contributed to patient deaths.[Ref]

Very common (10% or more): Fever/pyrexia (up to 65%), death (up to 14%), fatigue, asthenia, chills
Common (1% to 10%): Rigors, malaise, pain, infection, sepsis, chest pain, edema, influenza-like symptoms, bacterial infections, moniliasis, fungal infections, abscess, facial edema
Frequency not reported: Catheterization-related infection, hospitalization, drug accumulation in teeth and bones[Ref]


Very common (10% or more): Anemia (up to 33%), granulocytopenia (up to 17%), decreased hemoglobin
Common (1% to 10%): Marrow suppression, neutropenia, leukopenia, thrombocytopenia, platelet abnormalities, thrombosis, white blood cell abnormalities, lymphadenopathy
Uncommon (0.1% to 1%): Pancytopenia
Frequency not reported: Decreased absolute neutrophil count (ANC) to less than 0.5 x 10(9)/L, hemoglobin less than 7 g/dL[Ref]

Nervous system

Risk factors for drug-related seizures included underlying central nervous system conditions predisposing patients to seizures, impaired baseline renal function, and low total serum calcium. The rate of seizures did not increase with duration of therapy. At least 3 cases were reported with overdoses of this drug.[Ref]

Very common (10% or more): Headache (up to 26%), paresthesia, dizziness
Common (1% to 10%): Seizures/convulsion (including grand mal seizures), involuntary muscle contractions, hypoesthesia, neuropathy, tremor, ataxia, dementia, stupor, generalized spasms, sensory disturbances, meningitis, aphasia, abnormal coordination, leg cramps, electroencephalogram abnormalities, amnesia, somnolence, taste perversions, peripheral neuropathy
Uncommon (0.1% to 1%): Coma, other neurologic complications
Postmarketing reports: Encephalopathy[Ref]


Very common (10% or more): Rash
Common (1% to 10%): Increased sweating, pruritus, skin ulceration, seborrhea, erythematous rash, maculopapular rash, skin discoloration
Frequency not reported: Eosinophilic folliculitis
Postmarketing reports: Vesiculobullous eruptions, erythema multiforme, toxic epidermal necrolysis, Stevens-Johnson syndrome[Ref]

When toxic epidermal necrolysis or Stevens-Johnson syndrome was reported, patients were usually taking other agents associated with those reactions.[Ref]


Common (1% to 10%): Injection site pain, injection site inflammation[Ref]


Common (1% to 10%): Hypertension, palpitations, ECG abnormalities, sinus tachycardia, first degree atrioventricular block, nonspecific ST-T segment changes, hypotension, flushing, cerebrovascular disorder, thrombophlebitis
Uncommon (0.1% to 1%): Cardiac arrest, other cardiovascular complications
Frequency not reported: Reversible cardiac dysfunction, increased heart rate
Postmarketing reports: Ventricular arrhythmia, QT interval prolongation[Ref]

Reversible cardiac dysfunction was reported in a patient using this drug, who experienced shortness of breath, increased heart rate, and pulmonary edema, which reoccurred upon rechallenge. Serum electrolytes were within normal limits.

Thrombophlebitis in peripheral veins has been reported after infusion of undiluted drug solution.[Ref]


Common (1% to 10%): Abnormal hepatic function, increased ALT/SGPT, increased AST/SGOT, increased GGT[Ref]


Common (1% to 10%): Back pain, arthralgia, myalgia
Uncommon (0.1% to 1%): Increased creatine phosphokinase
Frequency not reported: Twitches
Postmarketing reports: Muscle disorders including myopathy, myositis, muscle weakness, rhabdomyolysis[Ref]


Common (1% to 10%): Lymphoma-like disorder, sarcoma[Ref]


Common (1% to 10%): Coughing, dyspnea, pneumonia, sinusitis, pharyngitis, rhinitis, respiratory disorders, respiratory insufficiency, pulmonary infiltration, stridor, pneumothorax, hemoptysis, bronchospasm
Frequency not reported: Pulmonary edema[Ref]


Common (1% to 10%): Depression, confusion, anxiety, insomnia, nervousness, agitation, aggression, hallucination
Postmarketing reports: Mental status changes[Ref]


Common (1% to 10%): Vision abnormalities, eye abnormalities, eye pain, conjunctivitis[Ref]


High levels of this drug are excreted in the urine and may be associated with significant irritation and ulceration in the genital area, especially after prolonged therapy.

Penile ulcerations have been reported to occur after a median of 11 days of induction therapy and 30 days of maintenance therapy, and healed within 6 days of drug discontinuation. Ulceration has been reported more often in uncircumcised patients.[Ref]

Common (1% to 10%): Albuminuria, dysuria, polyuria, urethral disorder, urinary retention, urinary tract infections, nocturia, genital discomfort/irritation and ulceration
Uncommon (0.1% to 1%): Hematuria
Frequency not reported: Local irritation/ulceration of penile epithelium, vulvovaginal ulceration, penile ulceration, vulvar erosion[Ref]


Uncommon (0.1% to 1%): Syndrome of inappropriate antidiuretic hormone secretion
Postmarketing reports: Diabetes insipidus


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Not all side effects for Foscavir may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

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