Names and pronunciation
(foss-kar′net) Foscavir
PDF page 599
Loading InternPractice…
Drug reference
(foss-kar′net) Foscavir
PDF page 599
Func. class.: Antiviral
PDF page 599
Chem. class.: Inorganic pyrophos- phate organic analog
PDF page 599
ACTION: Antiviral activity is produced by selective inhibition at the pyrophos- phate binding site on virus-specific DNA polymerases and reverse transcriptases at concentrations that do not affect cel- lular DNA polymerases
PDF page 599
USES: Treatment of CMV retinitis in patients with AIDS, treatment of acyclo- vir-resistant HSV infections; used with ganciclovir for relapsing patients
PDF page 599
CONTRAINDICATIONS: Hyper- sensitivity, CCr <0.4 mL/min/kg Precautions: Pregnancy, breastfeeding, children, geriatric patients, seizure dis- orders, severe anemia F
PDF page 599
Black Box Warning: Nephrotoxicity, electrolyte/mineral imbalances, seizures Black Box Warning: Increase: nephro- toxicity—acyclovir, cidofovir, CISplatin, gold compounds, tacrolimus, tenofovir, vancomycin, aminoglycosides, ampho- tericin B, NSAIDs, lithium, cycloSPORINE, pentamidine Increase: hypocalcemia—pentamidine, calcium products (decreases ionized calcium) Black Box Warning: Renal tubular dis- orders: I&O ratio, urine pH, serum cre- atinine at baseline, 3×/wk during initial therapy then 2×/wk thereafter; CCr at baseline, throughout treatment; if CCr <0.4 mL/min/kg, discontinue; provide adequate hydration before and during infusion to prevent toxicity • Blood counts q2wk; watch for decreas- ing granulocytes, HB; if low, therapy may have to be discontinued and restarted after hematologic recovery; blood trans- fusions may be required • Lesions in HSV Black Box Warning: Seizures: may be caused by alterations in minerals and electrolytes, monitor for seizures; monitor electrolytes and minerals (calcium, phos- phate, magnesium, potassium); watch closely for tetany during 1st administration • Electrolytes and minerals (calcium, phosphate, magnesium, potassium); watch closely for tetany during 1st administration • GI symptoms: nausea, vomiting, diar- rhea; severe symptoms may necessitate discontinuing product • Blood dyscrasias (anemia, granulocytope- nia): bruising, fatigue, bleeding, poor healing • Allergic reactions: flushing, rash, urti- caria, pruritus CMV retinitis • Culture (blood, urine, throat) should be performed before treatment; a nega- tive culture does not rule out CMV. Oph- thalmic exam should confirm diagnosis, another exam at conclusion of induction and q4wk during treatment. Monitor closely during therapy for tingling, numbness, paresthesias; if these occur, stop infusion, obtain lab sample for elec- trolytes • Pregnancy/breastfeeding: use only if ben- efits outweigh fetal risk; do not breastfeed
PDF pages 599, 600
SIDE EFFECTS CNS: Fever, dizziness, headache, sei- zures, fatigue, neuropathy, asthenia, encephalopathy, malaise, meningitis, paresthesia, depression, confusion, anxiety CV: ECG abnormalities, 1st-degree AV block, nonspecific ST-T segment changes, cerebrovascular disorder, cardiomyopathy, cardiac arrest, atrial fibrillation, HF, sinus tachycardia GI: Nausea, vomiting, diarrhea, anorexia, abdominal pain, pancreatitis GU: Acute renal failure, decreased CCr, increased serum creatinine, azotemia, diabetes insipidus, renal tubular disorders HEMA: Anemia, granulocytopenia, leu- kopenia, thrombocytopenia, thrombosis, neutropenia, lymphadenopathy INTEG: Rash, sweating, pruritus, skin discoloration RESP: Coughing, dyspnea, pneumonia, pulmonary infiltration, pneumothorax, hemoptysis SYST: Hypokalemia, hypocalcemia, hypomagnesemia; hypophosphatemia
PDF pages 599, 600
INTERACTIONS
PDF page 600
DOSAGE AND ROUTES Acyclovir-resistant HSV infections • Adult/adolescent (unlabeled): IV 40 mg/kg every 8-12 hr × 2-3 wk or until lesions are healed, max 120 mg/kg/day Cytomegalovirus (CMV) retinitis (AIDS) • Adult/adolescent: IV 90 mg/kg every 12 hr or 60 mg/kg every 8 hr × 3 wk (or until symptomatic improvement); main- tenance IV infusion 90-120 mg/kg over 2 hr daily, max 180 mg/kg/day (initial); 120 mg/kg/day (maintenance)
PDF page 599
Available forms: Inj 6000 mg/250 mL, 12,000 mg/500 mL (24 mg/mL)
PDF page 599
Administer: • Increased fluids before and during product administration to induce diure- sis, minimize renal toxicity Intermittent IV INFUSION route • Using infusion device at no more than 1 mg/kg/min; do not give by rapid or bolus IV; give by CVL or peripheral vein; standard 24 mg/mL sol may be used without dilution if using by CVL; dilute the 24 mg/mL sol to 12 mg/mL with D5W or NS if using peripheral vein • Manufacturer recommends product not be given with other medications in syringe or admixed
PDF page 599
Assess: HSV: characteristics of lesions baseline and daily during treatment
PDF page 600
Evaluate: • Therapeutic response: improvement in CMV retinitis, healing of HSV lesions
PDF page 600
CLINICAL CONSIDERATIONS
PDF page 600
Patient and caregiver information: • To call prescriber if sore throat, swol- len lymph nodes, malaise, fever occur, since other infections may occur • To report perioral tingling, numbness in extremities, and paresthesias • That serious product interactions may occur if OTC products are ingested; check first with prescriber • That product is not a cure but will control symptoms
PDF page 600
PHARMACOKINETICS 14%-17% protein bound, half-life 3 hr in normal renal function, 79%-92% excreted via kidneys, onset rapid, peak infusions end, duration up to 24 hr
PDF page 600
• Adult/adolescent (unlabeled): IV 40 mg/kg every 8-12 hr × 2-3 wk or until lesions are healed, max 120 mg/kg/day Cytomegalovirus (CMV) retinitis (AIDS)
PDF page 599
• Adult/adolescent: IV 90 mg/kg every 12 hr or 60 mg/kg every 8 hr × 3 wk (or until symptomatic improvement); main- tenance IV infusion 90-120 mg/kg over 2 hr daily, max 180 mg/kg/day (initial); 120 mg/kg/day (maintenance)
PDF page 599