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Drug Details

FAMVIR

• Drug Class Description
  Antivirals.
• Generic Name
  Famciclovir - genital herpes
• Presentation
  Film-coated tablet. 125 mg tablets: White, round, biconvex tablets, debossed with 'FAMVIR' or 'FV' on one side and 125 on the reverse side. 250 mg tablets: White, round, biconvex tablets, debossed with 'FAMVIR' or 'FV' on one side and 250 on the reverse side. 500 mg tablets: White, oval, biconvex tablets debossed with 'FAMVIR 500' or 'ORAVIR 500' or 'FV 500' on one side and plain on the reverse side. 750 mg tablets: White, oval, biconvex tablets debossed with 'FAMVIR 750' or 'FV 750' on one side and plain on the reverse side.
• Description
  Each tablet contains 125 mg, 250 mg, 500 mg or 750 mg famciclovir
• Indications
  

  125 mg tablets: For the treatment of acute recurrent genital herpes infections.

  250 mg tablets: For the treatment of herpes zoster (shingles) infections, first episode genital herpes infections and the suppression of recurrent genital herpes infections.

  500 mg tablets: Treatment of herpes zoster infections and treatment and suppression of herpes simplex infections in immunocompromised patients.

  750 mg tablets: For the treatment of herpes zoster (shingles) infections.

• Adult Dosage
  

  Dosage: Adults:

  Herpes zoster infections:

  - One 750 mg tablet once daily for seven days, or

  - One 250 mg tablet three times daily for seven days or alternatively three 250 mg tablets once a day for seven days. If the tablets are taken once a day they should be taken at approximately the same time each day.

  Initiation of treatment is recommended as soon as possible after rash onset.

  Herpes zoster infections in immunocompromised adults:

  One 500mg tablet three times daily for ten days. Initiation of treatment is recommended as soon as possible after rash onset.

  Herpes simplex infections in immunocompromised adults :

  Acute treatment: One 500 mg tablet three times daily for seven days. Initiation of treatment is recommended as soon as possible after rash onset.

  Suppression: A dose of 500 mg twice daily has been shown to be efficacious in HIV patients. Therapy should be interrupted periodically at intervals of six to twelve months in order to observe possible changes in the natural history of the disease.

  First-episode genital herpes infections:

  One 250 mg tablet three times daily for five days. Initiation of treatment is recommended as soon as possible after onset of lesions.

  Recurrent genital herpes infections:

  Acute treatment: One 125 mg tablet twice daily for five days. Initiation of treatment is recommended during the prodromal period or as soon as possible after onset of lesions.

  Suppression: One 250 mg tablet twice daily. Therapy should be interrupted periodically at intervals of six to twelve months in order to observe possible changes in the natural history of the disease.

  Elderly:

  Dosage modification is not required unless renal function is impaired.

  Renally impaired:

  As reduced clearance of penciclovir is related to reduced renal function, special attention should be given to dosage in patients with impaired renal function. The following modifications are recommended:

  For the treatment of herpes zoster infections and first-episode genital herpes infections:
  Creatinine clearance (ml/min/1.73m2 )	Dosage
  30-59	250 mg twice daily
  10-29	125 mg once daily
  For the treatment of acute recurrent genital herpes infections:
  Creatinine clearance (ml/min/1.73m2 )	Dosage
  30-59	No dose adjustment necessary
  10-29	125 mg once daily
  For the suppression of recurrent genital herpes infections:
  Creatinine clearance (ml/min/1.73m2 )	Dosage
  > 30	250 mg twice daily
  10-29	125 mg twice daily

  In renally impaired patients who are also immunocompromised:

  For the treatment of herpes zoster infections in immunocompromised patients:
  Creatinine clearance (ml/min/1.73m2 )	Dosage
  > 40	500 mg three times daily
  30-39	250 mg three times daily
  10-29	125 mg three times daily
  For the treatment of herpes simplex infections in immunocompromised patients:
  Creatinine clearance (ml/min/1.73m2 )	Dosage
  > 40	500 mg twice daily
  30-39	250 mg twice daily
  10-29	125 mg twice daily

  When only serum creatinine is available, a nomogram or the following formula (Cockcroft and Gault) should be used to estimate creatinine clearance.

  Formula to estimate creatinine clearance (ml/min/1.73 m² ):

  Renally impaired patients on haemodialysis:

  For a patient on haemodialysis, a dosage interval of 48 hours is recommended for periods between dialysis. Since four hours' haemodialysis results in approximately 75% reduction in plasma concentrations of penciclovir, a dose of famciclovir (250 mg for herpes zoster patients and 125 mg for herpes simplex patients) should be administered immediately following dialysis.

  Hepatically Impaired:

  Dosage modification is not required for patients with well compensated chronic liver disease. There is no information on patients with decompensated chronic liver disease; accordingly no precise dose recommendations can be made for this group of patients.

  Children:

  There are currently insufficient data on the safety and efficacy of Famvir in children and therefore its use in children is not recommended.

  Administration:

  Oral.

  Because the systemic availability (AUC) of penciclovir was not altered when famciclovir was administered with food, it appears that famciclovir can be taken without regard to meals.

• Child Dosage
  Not recommended.
• Contra Indications
  

  Famvir is contraindicated in patients with known hypersensitivity to famciclovir or other constituents of Famvir. It is also contraindicated in those patients who have shown hypersensitivity to penciclovir.

• Special Precautions
  

  Special attention should be paid to patients with impaired renal function as dosage adjustment is necessary. No special precautions are required for elderly patients with normal renal function and patients with well-compensated hepatic impairment.

  Famciclovir has not been studied in patients with severe uncompensated hepatic impairment.

  125 mg, 250 mg and 500 mg tablets: Genital herpes is a sexually transmitted disease. The risk of transmission is increased during acute episodes. Patients should avoid sexual intercourse when symptoms are present even if treatment with an antiviral has been initiated.

  250 mg and 500 mg tablets: During suppressive treatment with famciclovir, the frequency of viral shedding (both symptomatic and asymptomatic) may be reduced. However, the risk of viral transmission remains even during suppressive antiviral therapy and with protected intercourse, i.e. the use of condoms.

  Famvir 125 mg and 250 mg tablets contain lactose (26.9 mg and 53.7 mg respectively). Patients with rare hereditary problems of galactose intolerance, a severe lactase deficiency or glucose-galactose malabsorption should not take Famvir 125 mg or 250 mg tablets.

• Interactions
  

  Effects of other medicinal products on famciclovir

  Probenecid and other drugs that affect renal physiology could affect plasma levels of penciclovir.

  The conversion of the inactive metabolite 6-deoxy penciclovir (formed by deacetylation of famciclovir) to penciclovir is catalysed by aldehyde oxidase. Interactions with other drugs metabolized by his enzyme and / or inhibition this enzyme could potentially occur. Clinical interaction studies of famciclovir with cimetidine and promethazine, in vitro inhibitors of aldehyde oxidase, did not show relevant effects on the formation of penciclovir. However raloxifene, the most potent aldehyde oxidase inhibitor observed in vitro, could affect the formation of penciclovir.

  Effects of famciclovir on the other medicinal products

  Although famciclovir is only a weak inhibitor of aldehyde oxidase in vitro, interactions with drugs metabolized by aldehyde oxidase could potentially occur. Evidence from preclinical studies has shown no potential for induction of cytochrome P450 enzymes and inhibition of CYP3A4.

• Adverse Drug Reactions
  

  Famciclovir has been well tolerated in human studies. Headache and nausea have been reported in clinical trials. These were generally mild or moderate in nature and occurred at a similar incidence in patients receiving placebo treatment.

  The following table specifies the estimated frequency of adverse reactions based on all the spontaneous reports and literature cases that have been reported for Famvir since its introduction to the market.

  Adverse reactions (Table 1 ) are ranked under headings of frequency, using the following convention: very common ( .1/10 ); common ( 1/100,< 1/10 ); uncommon ( 1/1,000,< 1/100 ); rare ( 1/10,000,< 1/1,000 ) ;very rare ( < 1/10,000 ), including isolated reports.

  Table 1

  Blood and lymphatic disorders system
  Not known	Thrombocytopenia
  Psychiatric disorders
  Rare	Confusion (predominantly in the elderly)
  Very rare	Hallucinations
  Nervous system
  Rare	Headache
  Very rare	Dizziness, somnolence (predominantly in the elderly)
  Gastrointestinal disorders
  Rare	Nausea
  Very rare	Vomiting
  Hepatobiliary disorders
  Very rare	Cholestatic jaundice, abnormal liver function tests
  Skin and subcutaneous tissue disorders
  Very rare	Rash, pruritus, urticaria
  Not known	Serious skin reactions (e.g.erythema multiforme, Stevens-Johnson Syndrome, Toxic Epidermal Necrolysis)

  500 mg Tablets: Famciclovir has also been well tolerated in immunocompromised patients. Undesirable effects reported from clinical studies were similar to those reported in the immunocompetent population. Cases of abdominal pain, fever and rarely granulocytopenia and thrombocytopenia have been observed (granulocytopenia and thrombocytopenia have also been observed in immunocompromised patients not treated with famciclovir).