Drugs List

Therapeutic Indications

Uses

Varicella zoster virus infections - herpes zoster
Treatment of herpes zoster and ophthalmic zoster in immunocompetent adults.

Treatment of herpes zoster in immunocompromised adults.

Herpes simplex infections
Treatment of first and recurrent episodes of genital herpes in immunocompetent adults.

Treatment of recurrent episodes of genital herpes in immunocompromised adults.

Treatment of herpes simplex infections in immunocompromised adults.

Suppression of recurrent genital herpes in immunocompetent and immunocompromised adults.

Administration

For oral administration.

Can be taken without regard to meals.

Contraindications

Children under 18 years
Breastfeeding (see Lactation )
Galactosaemia

Precautions and Warnings

Use with caution in patients with severe hepatic impairment (see Dosage - Hepatic Impairment ).

In patients with renal impairment dosage adjustment is required (see Dosage - Renal Impairment).

Pregnancy (see Pregnancy) .

Advise patients with genital herpes to avoid sexual intercourse while symptoms persist even if treatment has been initiated.

In patients on suppressive treatment with famciclovir the risk of transmission of the virus is still possible even though the frequency of viral shedding is reduced.

Clinical response should be closely monitored, especially in immunocompromised patients. Intravenous anti-viral therapy should be considered if oral therapy is insufficient. Complicated herpes zoster (e.g. those with visceral involvement, disseminated zoster, motor neuropathies, encephalitis, cerebrovascular complications) , immunocompromised patients with ophthalmic zoster, and those at high risk for disease dissemination and visceral organ involvement should be treated with intravenous anti-viral therapy.

During suppressive treatment with antiviral agents, the frequency of viral shedding is significantly reduced. However, transmission is still possible. Therefore, in addition to therapy with famciclovir, it is recommended that patients use safer sex practices.

Dizziness, somnolence, confusion or other central nervous system disturbances may occur. This may impair the ability to perform skilled tasks. Advise patients not to drive or operate machinery if affected by the side effects of famciclovir.

Some formulations contain lactose and should with caution in use in patients with glucose-galactose malabsorption syndrome and lactose intolerance.

Not all available brands are licensed for all indications.

Pregnancy and Lactation

Pregnancy

Famciclovir should only be used in pregnancy if the potential benefit outweighs the risk to the foetus.

At the time of writing there is limited published experience concerning the use of famciclovir during human pregnancy. After administration famciclovir undergoes rapid biotransformation to penciclovir, its active metabolite. It is not known if famciclovir or penciclovir cross the human placenta, however because of its low molecular weight (321), passage should be expected. Carcinogenic but not teratogenic effects have been observed in animal studies with famciclovir but no effects on embryo / foetal development have been observed with either oral or intravenous administration to rats or rabbits (Briggs, 2011). Schaefer does not recommend the use of famciclovir during pregnancy due to insufficient data, however concludes its inadvertent use does not require termination of the pregnancy or invasive diagnostics (Schaefer, 2007).

The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14-17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).

Lactation

Famciclovir should not be used during breastfeeding.

Penciclovir, the active metabolite of famciclovir, is secreted into the breast milk of lactating rats achieving milk concentrations higher than plasma levels. No information is available on excretion into human breast milk. Famciclovir is probably excreted into human milk and because of its potential toxicity, women should probably not breastfeed (Briggs, 2011). In patients with HIV infection an additional consideration of the risk of virus transmission via the mother's milk is required (Schaefer, 2007).

Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1

Side Effects

Thrombocytopenia
Confusion
Hallucinations
Headache
Dizziness
Somnolence
Nausea
Vomiting
Abnormal liver function tests
Cholestatic jaundice
Rash
Pruritus
Urticaria
Erythema multiforme
Stevens-Johnson syndrome
Toxic epidermal necrolysis
Abdominal pain
Diarrhoea
Fatigue
Sweating
Constipation
Fever
Skin reactions
Angioedema
Angioedema of tongue, lips and face

Presentation

Tablets containing famciclovir 125mg.
Tablets containing famciclovir 250mg.
Tablets containing famciclovir 500mg.
Tablets containing famciclovir 750mg.

Drugs List

Therapeutic Indications

Uses

Varicella zoster virus infections - herpes zoster
Treatment of herpes zoster and ophthalmic zoster in immunocompetent adults.

Treatment of herpes zoster in immunocompromised adults.

Herpes simplex infections
Treatment of first and recurrent episodes of genital herpes in immunocompetent adults.

Treatment of recurrent episodes of genital herpes in immunocompromised adults.

Treatment of herpes simplex infections in immunocompromised adults.

Suppression of recurrent genital herpes in immunocompetent and immunocompromised adults.

Dosage

Initiation of treatment is recommended as soon as diagnosis has been made and/or prodromal symptoms occur.

Adults

Patients with Renal Impairment

Patients with Hepatic Impairment

Administration

For oral administration.

Can be taken without regard to meals.

Contraindications

Children under 18 years
Breastfeeding (see Lactation )
Galactosaemia

Precautions and Warnings

Use with caution in patients with severe hepatic impairment (see Dosage - Hepatic Impairment ).

In patients with renal impairment dosage adjustment is required (see Dosage - Renal Impairment).

Pregnancy (see Pregnancy) .

Advise patients with genital herpes to avoid sexual intercourse while symptoms persist even if treatment has been initiated.

In patients on suppressive treatment with famciclovir the risk of transmission of the virus is still possible even though the frequency of viral shedding is reduced.

Clinical response should be closely monitored, especially in immunocompromised patients. Intravenous anti-viral therapy should be considered if oral therapy is insufficient. Complicated herpes zoster (e.g. those with visceral involvement, disseminated zoster, motor neuropathies, encephalitis, cerebrovascular complications) , immunocompromised patients with ophthalmic zoster, and those at high risk for disease dissemination and visceral organ involvement should be treated with intravenous anti-viral therapy.

During suppressive treatment with antiviral agents, the frequency of viral shedding is significantly reduced. However, transmission is still possible. Therefore, in addition to therapy with famciclovir, it is recommended that patients use safer sex practices.

Dizziness, somnolence, confusion or other central nervous system disturbances may occur. This may impair the ability to perform skilled tasks. Advise patients not to drive or operate machinery if affected by the side effects of famciclovir.

Some formulations contain lactose and should with caution in use in patients with glucose-galactose malabsorption syndrome and lactose intolerance.

Not all available brands are licensed for all indications.

Pregnancy and Lactation

Pregnancy

Famciclovir should only be used in pregnancy if the potential benefit outweighs the risk to the foetus.

At the time of writing there is limited published experience concerning the use of famciclovir during human pregnancy. After administration famciclovir undergoes rapid biotransformation to penciclovir, its active metabolite. It is not known if famciclovir or penciclovir cross the human placenta, however because of its low molecular weight (321), passage should be expected. Carcinogenic but not teratogenic effects have been observed in animal studies with famciclovir but no effects on embryo / foetal development have been observed with either oral or intravenous administration to rats or rabbits (Briggs, 2011). Schaefer does not recommend the use of famciclovir during pregnancy due to insufficient data, however concludes its inadvertent use does not require termination of the pregnancy or invasive diagnostics (Schaefer, 2007).

The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14-17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).

Lactation

Famciclovir should not be used during breastfeeding.

Penciclovir, the active metabolite of famciclovir, is secreted into the breast milk of lactating rats achieving milk concentrations higher than plasma levels. No information is available on excretion into human breast milk. Famciclovir is probably excreted into human milk and because of its potential toxicity, women should probably not breastfeed (Briggs, 2011). In patients with HIV infection an additional consideration of the risk of virus transmission via the mother's milk is required (Schaefer, 2007).

Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1

Effects on Ability to Drive and Operate Machinery

The ability to drive or operate machinery may be affected by side effects such as dizziness, somnolence, confusion or other central nervous system disturbances.

Counselling

Advise patients about safe sex during acute and chronic viral infections to prevent transmission.

Advise patients that the ability to drive or operate machinery may be affected by side effects such as dizziness, somnolence, confusion or other central nervous system disturbances.

Side Effects

Thrombocytopenia
Confusion
Hallucinations
Headache
Dizziness
Somnolence
Nausea
Vomiting
Abnormal liver function tests
Cholestatic jaundice
Rash
Pruritus
Urticaria
Erythema multiforme
Stevens-Johnson syndrome
Toxic epidermal necrolysis
Abdominal pain
Diarrhoea
Fatigue
Sweating
Constipation
Fever
Skin reactions
Angioedema
Angioedema of tongue, lips and face

Overdosage

It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

The following number will direct the caller to the relevant local centre (0844) 892 0111

Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).

Shelf Life and Storage

Store below 30 degrees C.

Further Information

Last Full Review Date: May 2012

Reference Sources

Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 9th edition (2011) ed. Briggs, G., Freeman, R. and Yaffe, S. Lippincott Williams & Wilkins, Philadelphia.

Summary of Product Characteristics: Famciclovir 125mg tablets. Actavis UK Ltd. Revised September 2011.
Summary of Product Characteristics: Famciclovir 250mg tablets. Actavis UK Ltd. Revised September 2011.
Summary of Product Characteristics: Famciclovir 500mg tablets. Actavis UK Ltd. Revised September 2011.
Summary of Product Characteristics: Famciclovir 125mg film-coated tablets. Winthrop Pharmaceuticals UK Ltd. Revised September 2009.
Summary of Product Characteristics: Famciclovir 250mg film-coated tablets. Winthrop Pharmaceuticals UK Ltd. Revised September 2009.
Summary of Product Characteristics: Famciclovir 750mg film-coated tablets. Winthrop Pharmaceuticals UK Ltd. Revised September 2009.
Summary of Product Characteristics: Famvir 125mg Tablets. Novartis Pharmaceuticals UK Ltd. Revised September 2011.
Summary of Product Characteristics: Famvir 250mg Tablets. Novartis Pharmaceuticals UK Ltd. Revised September 2011.
Summary of Product Characteristics: Famvir 500mg Tablets. Novartis Pharmaceuticals UK Ltd. Revised September 2011.

NICE Evidence Services Available at: www.nice.org.uk Last accessed: 15 September 2017

US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
Available at: https://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT
Famciclovir. Last revised: February 3, 2009
Last accessed: May 16, 2012.