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Sunday, February 6, 2011

Acyclovir (acycloguanosine)

Posted by Sampil 9:44 PM, under | No comments

acyclovir (acycloguanosine)
(ay sye' kloe ver)
Alti-Acyclovir (CAN), Avirax (CAN), Zovirax

Pregnancy Category B

Drug class
Antiviral
Purine nucleoside analogue

Therapeutic actions
Antiviral activity; inhibits viral DNA replication.

Indications
·        Initial and recurrent mucosal and cutaneous HSV 1 and 2 and varicella zoster infections in immunocompromised patients
·        Severe initial and recurrent genital herpes infections in selected patients
·        Herpes simplex encephalitis
·        Treatment of neonatal herpes simplex virus infections
·        Acute treatment of herpes zoster (shingles) and chickenpox
·        Ointment: Initial HSV genital infections; limited mucocutaneous HSV infections in immunocompromised patients
·        Cream: Recurrent herpes labialis (cold sores) in patients > 12 yr
·        Unlabeled uses: Cytomegalovirus and HSV infection following transplant, herpes simplex infections, varicella pneumonia, disseminated primary eczema herpeticum

Contraindications and cautions
·        Contraindicated with allergy to acyclovir, seizures, CHF, renal disease, lactation.
·        Use cautiously with pregnancy.

Available forms
Tablets—400, 800 mg; capsules—200 mg; suspension—200 mg/5 mL; powder for injection—500 mg/vial, 1,000 mg/vial; injection—50 mg/mL; ointment—50 mg/g; cream—50 mg/g

Dosages
ADULTS
Parenteral
5–10 mg/kg infused IV over 1 hr, q 8 hr (15 mg/kg/day) for 7–10 days.
Oral
·        Initial genital herpes: 200 mg q 4 hr while awake (1,000 mg/day) for 10 days.
·        Long-term suppressive therapy: 400 mg bid for up to 12 mo.
·        Acute herpes zoster: 800 mg q 4 hr for 7–10 days.
·        Chickenpox: 800 mg qid for 5 days.
PEDIATRIC PATIENTS
Parenteral
HSV infections < 12 yr: 10 mg/kg infused IV over 1 hr q 8 hr for 7 days.
Shingles, HSV encephalitis: 20 mg/kg IV over 1 hr q 8 hr for 10 days.
Neonatal HSV: 10 mg/kg infused over 1 hr q 8 hr for 10 days.
Oral
< 2 yr: Safety not established.
> 2 yr and < 40 kg: 20 mg/kg per dose qid (80 mg/kg/day) for 5 days.
> 40 kg: Use adult dosage.
> 12 yr: Use adult dosage.
GERIATRIC PATIENTS OR PATIENTS WITH RENAL IMPAIRMENT
Oral
For creatinine clearance < 10 mL/min, 200 mg q 12 hr.
IV
Creatinine Clearance (mL/min)
Dosage (IV)
> 50
5 mg/kg q 8 hr
25–50
5 mg/kg q 12 hr
10–25
5 mg/kg daily
0–10
2.5 mg/kg daily
Topical
Ointment (all ages): Apply sufficient quantity to cover all lesions 6 times/day (q 3 hr) for 7 days; 1.25-cm (0.5-in) ribbon of ointment covers 2.5 cm2 (4 in2) surface area.
Cream (> 12 yr): Apply sufficient quantity to cover all lesions 5 times/day for 4 days.

Pharmacokinetics
Route
Onset
Peak
Duration
Oral
Varies
1.5–2 hr
Not known
IV
Immediate
1 hr
8 hr
Topical
Absorption is minimal


Metabolism: T1/2: 2.5–5 hr
Distribution: Crosses placenta; enters breast milk
Excretion: Unchanged in urine

IV facts
Preparation: Reconstitute 500 mg vial in 10 mL sterile water for injection or bacteriostatic water for injection containing benzyl alcohol, 1,000 mg vial in 20 mL; concentration will be 50 mg/mL. Do not dilute drug with bacteriostatic water containing parabens. Use reconstituted solution within 12 hr; dilute IV solution to concentration of 7 mg/mL or less. Do not use biologic or colloidal fluids such as blood products or protein solutions. Warm drug to room temperature to dissolve precipitates formed during refrigeration.
Infusion: Administer by slow IV infusion of parenteral solutions; avoid bolus or rapid injection. Infuse over at least 1 hr to avoid renal damage.
Incompatibilities: Do not mix with diltiazem, dobutamine, dopamine, fludarabine, foscarnet, idarubicin, meperidine, morphine, ondansetron, piperacillin, sargramostim, vinorelbine.

Adverse effects
Systemic administration
·        CNS: Headache, vertigo, depression, tremors, encephalopathic changes
·        Dermatologic: Inflammation or phlebitis at injection sites, rash, hair loss
·        GI: Nausea, vomiting, diarrhea, anorexia
·        GU: Crystalluria with rapid IV administration, hematuria
Topical administration
·        Dermatologic: Transient burning at site of application

Interactions
Systemic administration
·        Increased effects with probenecid
·        Increased nephrotoxicity with other nephrotoxic drugs
·        Extreme drowsiness with zidovudine

Nursing considerations
Assessment
·        History: Allergy to acyclovir, seizures, CHF, renal disease, lactation, pregnancy
·        Physical: Skin color, lesions; orientation; BP, P, auscultation, perfusion, edema; R, adventitious sounds; urinary output; BUN, creatinine clearance
Interventions
Systemic administration
·        Ensure that the patient is well hydrated.
Topical administration
·        Start treatment as soon as possible after onset of signs and symptoms.
·        Wear a rubber glove or finger cot when applying drug.

Teaching points
Systemic administration
·        Complete the full course of oral therapy, and do not exceed the prescribed dose.
·        Oral acyclovir is not a cure for your disease but should make you feel better.
·        Avoid sexual intercourse while visible lesions are present.
·        You may experience these side effects: Nausea, vomiting, loss of appetite, diarrhea; headache, dizziness.
·        Report difficulty urinating, rash, increased severity or frequency of recurrences.
Topical administration
·        Wear rubber gloves or finger cots when applying the drug to prevent autoinoculation of other sites and transmission to others.
·        This drug does not cure the disease; application during symptom-free periods will not prevent recurrences.
·        Avoid sexual intercourse while visible lesions are present.
·        This drug may cause burning, stinging, itching, rash; notify your physician if these are pronounced.

Adverse effects in Italic are most common; those in Bold are life-threatening.

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