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(foss-kar-net) ,


(trade name)


Therapeutic: antivirals
Pregnancy Category: C


Treatment of cytomegalovirus (CMV) retinitis in HIV-infected patients (alone or with ganciclovir).Treatment of acyclovir-resistant mucocutaneous herpes simplex virus (HSV) infections in immunocompromised patients.


Prevents viral replication by inhibiting viral DNA-polymerase and reverse transcriptase.

Therapeutic effects

Virustatic action against susceptible viruses including CMV.


Absorption: IV administration results in complete bioavailability.
Distribution: Variable penetration into CSF. May concentrate in and be slowly released from bone.
Metabolism and Excretion: 80–90% excreted unchanged in urine.
Half-life: 3 hr (in patients with normal renal function); longer half-life of 90 hr may reflect release of drug from bone.

Time/action profile

IVrapidend of infusion8–24 hr


Contraindicated in: Hypersensitivity.
Use Cautiously in: Renal impairment (dose ↓ required if CCr ≤1.4–1.6 mL/min/kg; see product information);History of seizures; Obstetric / Lactation / Pediatric: Safety not established.

Adverse Reactions/Side Effects

Central nervous system

  • seizures (life-threatening)
  • headache (most frequent)
  • anxiety
  • confusion
  • dizziness
  • fatigue
  • malaise
  • mental depression
  • weakness

Ear, Eye, Nose, Throat

  • conjunctivitis
  • eye pain
  • vision abnormalities


  • coughing
  • dyspnea


  • chest pain
  • ECG abnormalities
  • edema
  • palpitations


  • diarrhea (most frequent)
  • nausea (most frequent)
  • vomiting (most frequent)
  • abdominal pain
  • abnormal taste sensation
  • anorexia
  • constipation
  • dyspepsia


  • renal failure (most frequent)
  • albuminuria
  • dysuria
  • nocturia
  • polyuria
  • urinary retention


  • ↑ sweating
  • pruritus
  • rash
  • skin ulceration

Fluid and Electrolyte

  • hypocalcemia (most frequent)
  • hypokalemia (most frequent)
  • hypomagnesemia (most frequent)
  • hyperphosphatemia
  • hypophosphatemia


  • anemia (most frequent)
  • granulocytopenia
  • leukopenia


  • pain/inflammation at injection site


  • arthralgia (most frequent)
  • myalgia (most frequent)
  • back pain
  • involuntary muscle contraction


  • ataxia
  • hypoesthesia
  • neuropathy
  • paresthesia
  • tremor


  • fever (most frequent)
  • chills
  • flu-like syndrome
  • lymphoma
  • sarcoma


Drug-Drug interaction

Concurrent use with parenteral pentamidine may result in severe, life-threatening hypocalcemia.Risk of nephrotoxicity may be ↑ by concurrent use of other nephrotoxic agents (amphotericin B, aminoglycosides ).


Intravenous (Adults) CMV retinitis—60 mg/kg q 8 hr or 90 mg/kg q 12 hr for 2–3 wk, then 90–120 mg/kg/day as a single dose. Dose ↓ required for any degree of renal impairment; HSV—40 mg/kg q 8–12 hr for 2–3 wk or until healing occurs.

Availability (generic available)

Solution for injection: 24 mg/mL

Nursing implications

Nursing assessment

  • CMV Retinitis: Diagnosis of CMV retinitis should be determined by ophthalmoscopy before treatment with foscarnet. Ophthalmologic examinations should also be performed at the conclusion of induction and every 4 wk during maintenance therapy.
  • Culture for CMV (urine, blood, throat) may be taken before administration. However, a negative CMV culture does not rule out CMV retinitis.
  • HSV Infections: Assess lesions before and daily during therapy.
  • Lab Test Considerations: Monitor serum creatinine before and 2–3 times weekly during induction therapy and at least once every 1–2 wk during maintenance therapy. Monitor 24-hr CCr before and periodically throughout therapy. If CCr drops below 0.4 mL/min/kg, discontinue foscarnet.
    • Monitor serum calcium, magnesium, potassium, and phosphorus before and 2–3 times weekly during induction therapy and at least weekly during maintenance therapy. May cause ↓ concentrations.
    • May cause anemia, granulocytopenia, leukopenia, and thrombocytopenia. May cause ↑ AST and ALT levels and abnormal A-G ratios.

Potential Nursing Diagnoses

Risk for infection (Indications)


  • Adequately hydrate patient with 750–1000 mL of 0.9% NaCl or D5W before first infusion to establish diuresis, then administer 750–1000 mL with 120 mg/kg of foscarnet or 500 mL with 40–60 mg/kg of foscarnet with each dose to prevent renal toxicity.
  • Intravenous Administration
  • pH: 7.4.
  • Intermittent Infusion: Diluent: May be administered via central line undiluted. If administered via peripheral line, must be diluted with D5W or 0.9% NaCl to prevent vein irritation. Do not administer solution that is discolored or contains particulate matter. Use diluted solution within 24 hr.Concentration: Undiluted: 24 mg/mL; Diluted: 12 mg/mL.
    • Dose is based on patient weight; excess solution may be discarded from bottle before administration to prevent overdosage.
    • Patients who experience progression of CMV retinitis during maintenance therapy may be retreated with induction therapy followed by maintenance therapy.
  • Rate: Administer at a rate not to exceed 1 mg/kg/min.
    • Infuse solution via infusion pump to ensure accurate infusion rate.
  • Y-Site Compatibility: aldesleukin, amikacin, aminophylline, ampicillin, anidulafungin, aztreonam, bivalirudin, bleomycin, carboplatin, carmustine, cefazolin, cefoperazone, cefoxitin, ceftazidime, ceftriaxone, cefuroxime, chloramphenicol, cisplatin, clindamycin, cyclophosphamide, cytarabine, dactinomycin, daptomycin, dexamethasone sodium phosphate, dexmedetomidine, diltiazem, docetaxel, dopamine, doripenem, doxacurium, ertapenem, erythromycin lactobionate, etoposide, etoposide phosphate, fenoldopam, fluconazole, flucytosine, fludarabine, fluorouracil, furosemide, gemcitabine, gentamicin, granisetron, heparin, hydrocortisone, hydromorphone, ifosfamide, imipenen-cilastatin, irinotecan, linezolid, mechlorethamine, methotrexate, metoclopramide, metronidazole, morphine, nafcillin, nesiritide, octreotide, oxacillin, oxaliplatin, oxytocin, paclitaxel, palonosetron, pamidronate, pantoprazole, pemetrexed, penicillin G potassium, phenytoin, piperacillin/tazobactam, potassium acetate, ranitidine, tacrolimus, teniposide, thiotepa, ticarcillin/clavulanate, tigecycline, tirofiban, tobramycin, vincristine, voriconazole, zoledronic acid
  • Y-Site Incompatibility: Manufacturer recommends that foscarnet not be administered concurrently with other drugs or solutions in the same IV catheter except D5W or 0.9% NaClacyclovir, amphotericin B colloidal, amphotericin B lipid complex, caspofungin, diazepam, digoxin, diphenhydramine, dobutamine, doxorubicin, droperidol, epirubicin, ganciclovir, haloperidol, idarubicin, leucovorin, midazolam, mitoxantrone, mycophenolate, pentamidine, prochlorperazine, promethazine, vinorelbine

Patient/Family Teaching

  • Inform patient that foscarnet is not a cure for CMV retinitis. Progression of retinitis may continue in immunocompromised patients during and after therapy. Advise patients to have regular ophthalmologic exams.
  • Advise patient to notify health care professional immediately if perioral tingling or numbness in the extremities or paresthesia occurs during or after infusion. If these signs of electrolyte imbalance occur during administration, infusion should be stopped and lab samples for serum electrolyte concentrations obtained immediately.
  • Emphasize the importance of frequent follow-up exams to monitor renal function and electrolytes.

Evaluation/Desired Outcomes

  • Management of the symptoms of CMV retinitis in patients with AIDS.
  • Crusting over and healing of skin lesions in HSV infections.


A trademark for the drug foscarnet sodium.


a trademark for an antiviral drug (foscarnet) used in the treatment of cytomegalovirus retinitis in conjunction with ganciclovir and for the treatment of herpes simplex infections when acyclovir fails.


A brand name for FOSCARNET.
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Hospira granted exclusive rights to market, promote and distribute Foscavir in the US
50] Virus Foscavir 50-800 [micro]mol/L Cytomegalovirus 5-443 [micro]mol/L Herpes simplex mutants Acyclovir 0.
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Last year, the program added several medications for people with HIV/AIDS, including Videx, Hivid, Zovirax, Foscavir and Cipro.
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