Foscarnet sodium
Foscarnet sodium (Foscavir)
Foscarnet sodium
(fos- KAR-net)
Pregnancy Category: C Foscavir (Rx)

Classification: Antiviral agent

See Also: See also Antiviral Agents .

Action/Kinetics: Inhibits replication of all known herpes viruses by selective inhibition at the pyrophosphate binding site on virus-specific DNA polymerases and reverse transcriptases at levels that do not affect cellular DNA polymerases. Active against herpes simplex virus mutants deficient in thymidine kinase. CMV strains resistant to ganciclovir may be sensitive to foscarnet; viral reactivation of CMV occurs after termination of foscarnet therapy. The latent state of any of the human herpes viruses is not sensitive to foscarnet. Believed to accumulate in human bone and has variable penetration into the CSF. t 1/2, plasma: About 3 hr. Approximately 80%-90% of IV foscarnet is excreted unchanged through the urine.

Uses: Treatment of CMV retinitis in clients with AIDS. Treatment of acyclovir-resistant HSV infections in immunocompromised clients. With ganciclorvir in those who have relapsed after monotherapy with either drug.

Special Concerns: Use with caution during lactation and in clients with impaired renal function (the effects of the drug have not been determined in clients with a C _CR < 50 mL/min or serum creatinine > 2.8 mg/dL). Use with caution with drugs that alter serum calcium levels as foscarnet decreases serum levels of ionized calcium. Safety and effectiveness have not been determined in children, for the treatment of other CMV infections such as pneumonitis or gastroenteritis, for congenital or neonatal CMV disease, and in nonimmunocompromised clients. Transient changes in electrolytes may increase the risk of cardiac disturbances and seizures. Side effects such as renal impairment, electrolyte abnormalities, and seizures may contribute to client death. The drug is not a cure for HSV infections and relapse occurs in most clients. Repeated treatment has led to the development of viral resistance.

Side Effects: GU: Renal impairment (most common), albuminuria, dysuria, polyuria, urinary retention, urethral disorder, UTIs, acute renal failure nocturia, hematuria, glomerulonephritis, urinary frequency, toxic nephropathy, nephrosis, urinary incontinence, pyelonephritis, renal tubular disorders, urethral irritation, uremia, perineal pain in women, penile inflammation. Metabolic/Electrolyte: Hypocalcemia, hypokalemia, hypomagnesemia, hypophosphatemia, hyponatremia, hyperphosphatemia, hypercalcemia, acidosis, thirst, decreased weight, dehydration, glycosuria, diabetes mellitus, abnormal glucose tolerance, hypochloremia, hypervolemia, hypoproteinemia. Hematologic: Anemia (one-third of clients), granulocytopenia, neutropenia, leukopenia, thrombocytopenia, platelet abnormalities, thrombosis, WBC abnormalities, lymphadenopathy, coagulation disorders, decreased coagulation factors, decreased prothrombin, hypochromic anemia, pancytopenia, hemolysis, leukocytosis, cervical lymphadenopathy, lymphopenia. Body as a whole: Fever, fatigue, asthenia, pain, infection, rigors, malaise, sepsis, death, back or chest pain, cachexia, flu-like symptoms, edema, bacterial or fungal infections, abscess, moniliasis, leg edema, peripheral edema, hypothermia, syncope, substernal chest pain, ascites, malignant hyperpyrexia herpes simplex, viral infections, toxoplasmosis. CNS: Headache, dizziness, seizures (including tonic-clonic) tremor, ataxia, dementia, stupor, meningitis, aphasia, abnormal coordination, EEG abnormalities, vertigo, coma, encephalopathy, dyskinesia, extrapyramidal disorders, hemiparesis, paraplegia, speech disorders, tetany, cerebral edema, depression, confusion, anxiety, insomnia, somnolence, amnesia, aggressive reaction, nervousness, agitation, hallucinations, impaired concentration, emotional liability, psychosis, suicide attempt delirium, sleep disorders, personality disorders. Peripheral nervous system: Hypesthesia, neuropathy, sensory disturbances, generalized spasms, abnormal gait, hyperesthesia, hypertonia, hyperkinesia, vocal cord paralysis, hyporeflexia, hyperreflexia, neuralgia, neuritis, peripheral neuropathy. Musculoskeletal: Arthralgia, myalgia, involuntary muscle contractions, leg cramps, arthrosis, synovitis, torticollis. GI: N&V;, diarrhea, anorexia, abdominal pain, dry mouth, dysphagia, dyspepsia, rectal hemorrhage, constipation, melena, flatulence, pancreatitis, ulcerative stomatitis, enteritis, glossitis, enterocolitis, proctitis, stomatitis, tenesmus, pseudomembranous colitis, gastroenteritis, oral leukoplakia, oral hemorrhage, rectal disorders, colitis, duodenal ulcer, hematemesis, paralytic ileus, ulcerative proctitis, tongue ulceration, esophageal ulceration. Hepatic: Abnormal hepatic function, cholecystitis, cholelithiasis, hepatitis, hepatosplenomegaly, cholestatic hepatitis, jaundice. CV: Hypertension, palpitations, sinus tachycardia, first degree AV block, nonspecific ST-T segment changes, hypotension, flushing, cerebrovascular disorder, cardiomyopathy, cardiac failure, cardiac arrest bradycardia, arrhythmias, extrasystole, atrial fibrillation, phlebitis, superficial thrombophlebitis of arm, mesenteric vein thrombophlebitis. Respiratory: Cough, dyspnea, pneumonia, sinusitis, rhinitis, pharyngitis, respiratory insufficiency, pulmonary infiltration, pulmonary embolism pneumothorax, hemoptysis, stridor, bronchospasm, laryngitis, bronchitis, respiratory depression, pleural effusion, pulmonary hemorrhage pneumonitis. Ophthalmic: Visual field defects, nystagmus, periorbital edema, eye pain, conjunctivitis, diplopia, blindness, retinal detachment, mydriasis, photophobia. Ear: Deafness, earache, tinnitus, otitis. Dermatologic: Increased sweating, rash, skin ulceration, pruritus, seborrhea, erythematous rash, maculopapular rash, facial edema, skin discoloration, acne, alopecia, dermatitis, anal pruritus, genital pruritus, aggravated psoriasis, psoriaform rash, skin disorders, dry skin, urticaria, skin hypertrophy, verruca. Miscellaneous: Epistaxis, taste perversions, pain or inflammation at injection site, lymphoma-like disorder, sarcoma, malignant lymphoma ADH disorders, decreased gonadotropins, gynecomastia.

Laboratory Test Alterations: Alkaline phosphatase, AST, ALT, LDH, BUN, CPK, serum creatinine. C _CR. Abnormal X-ray. Abnormal A-G ratio.

Overdose Management: Symptoms: Extensions of the preceding side effects. Of most concern are development of seizures renal function impairment, paresthesias in limbs or periorally, and electrolyte disturbances especially involving calcium and phosphate. Treatment: Monitor the client for S&S; of electrolyte imbalance and renal impairment. Symptomatic treatment. Hemodialysis and hydration may be of some benefit.

Drug Interactions: Aminoglycosides / Elimination of foscarnet risk of renal impairment Amphotericin B / Elimination of foscarnet risk of renal impairment AZT / Risk of anemia Didanosine / Elimination of foscarnet risk of renal impairment Pentamidine, IV / Elimination of foscarnet risk of renal impairment; also, pentamidine causes hypocalcemia

How Supplied: Injection: 24 mg/mL

Dosage
?IV Infusion CMV retinitis in AIDS.
Individualized, initial, normal renal function: Either 60 mg/kg over a minimum of 1 hr q 8 hr or 90 mg/kg q 12 hr for 2-3 weeks, depending on the response. Maintenance: 90-120 mg/kg/day (depending on renal function) given as an IV infusion over 2 hr. Start most clients on the 90-mg/kg/day dose; however, consider increasing the dose to 120 mg/kg/day due to progression of retinitis.
Acyclovir-resistant HSV infections in immunocompromised clients.
Initial: 40 mg/kg for clients with normal renal function given IV at a constant rate over a minimum of 1 hr q 8 or 12 hr for 2 to 3 weeks or until lesions are healed. Maintenance: See dose for CMV retinitis.