Symptoms and signs
Zovirax 5% is only partly absorbed in the gastrointestinal tract. Patients have ingested overdoses of up to 20g Zovirax 5% on a single occasion, usually without toxic effects. Accidental, repeated overdoses of oral Zovirax 5% over several days have been associated with gastrointestinal effects (such as nausea and vomiting) and neurological effects (headache and confusion).
Overdosage of intravenous Zovirax 5% has resulted in elevations of serum creatinine, blood urea nitrogen and subsequent renal failure. Neurological effects including confusion, hallucinations, agitation, seizures and coma have been described in association with intravenous overdosage.
Management
Patients should be observed closely for signs of toxicity. Haemodialysis significantly enhances the removal of Zovirax 5% from the blood and may, therefore, be considered a management option in the event of symptomatic overdose.
Symptoms and signs:- Aciclovir is only partly absorbed in the gastrointestinal tract. Patients have ingested overdoses of up to 20g aciclovir on a single occasion, usually without toxic effects. Accidental, repeated overdoses of oral aciclovir over several days have been associated with gastrointestinal effects (such as nausea and vomiting) and neurological effects (headache and confusion).
Overdosage of intravenous aciclovir has resulted in elevations of serum creatinine, blood urea nitrogen and subsequent renal failure. Neurological effects including confusion, hallucinations, agitation, seizures and coma have been described in association with intravenous overdosage.
Management:- Patients should be observed closely for signs of toxicity. Haemodialysis significantly enhances the removal of aciclovir from the blood and may, therefore, be considered a management option in the event of symptomatic overdose.
Not applicable.
None known.
Prolonged or repeated courses of Zovirax 5% in severely immune-compromised individuals may result in the selection of virus strains with reduced sensitivity, which may not respond to continued Zovirax 5% treatment.
Hydration status: Care should be taken to maintain adequate hydration in patients receiving high oral doses of Zovirax 5%.
The risk of renal impairment is increased by use with other nephrotoxic drugs.
The data currently available from clinical studies is not sufficient to conclude that treatment with Zovirax 5% reduces the incidence of chickenpox-associated complications in immunocompetent patients.
Paediatric population:
Oral Zovirax 5% should be used in paediatric population mainly for the treatment of non-severe skin and mucosa HSV infections. For the treatment of neonatal HSV and severe HSV infections in immunocompromised children IV Zovirax 5% should be used.
4.5 Interaction with other medicinal products and other forms of interactionZovirax 5% is eliminated primarily unchanged in the urine via active renal tubular secretion. Any drugs administered concurrently that compete with this mechanism may increase Zovirax 5% plasma concentrations.
Probenecid and cimetidine increase the AUC of Zovirax 5% by this mechanism, and reduce Zovirax 5% renal clearance. Similarly increases in plasma AUCs of Zovirax 5% and of the inactive metabolite of mycophenolate mofetil, an immunosuppresant agent used in transplant patients have been shown when the drugs are co administered. However no dosage adjustment is necessary because of the wide therapeutic index of Zovirax 5%.
An experimental study on five male subjects indicates that concomitant therapy with Zovirax 5% increases AUC of totally administered theophylline with approximately 50%. It is recommended to measure plasma concentrations during concomitant therapy with Zovirax 5%.
4.6 Fertility, pregnancy and lactationPregnancy
The use of Zovirax 5% should be considered only when the potential benefits outweigh the possibility of unknown risks. A post-marketing Zovirax 5% pregnancy registry has documented pregnancy outcomes in women exposed to any formulation of Zovirax 5%. The registry findings have not shown an increase in the number of birth defects amongst Zovirax 5% exposed subjects compared with the general population, and any birth defects showed no uniqueness or consistent pattern to suggest a common cause. Systemic administration of Zovirax 5% in internationally accepted standard tests did not produce embryotoxic or teratogenic effects in rabbits, rats or mice. In a non-standard test in rats, foetal abnormalities were observed but only following such high subcutaneous doses that maternal toxicity was produced. The clinical relevance of these findings is uncertain.
Caution should however be exercised by balancing the potential benefits of treatment against any possible hazard.
Breastfeeding
Following oral administration of 200 mg Zovirax 5% five times a day, Zovirax 5% has been detected in breast milk at concentrations ranging from 0.6 to 4.1 times the corresponding plasma levels. These levels would potentially expose nursing infants to Zovirax 5% dosages of up to 0.3 mg/kg/day. Caution is therefore advised if Zovirax 5% is to be administered to a nursing woman.
Fertility
There is no information on the effect of Zovirax 5% on human female fertility.
In a study of 20 male patients with normal sperm count, oral Zovirax 5% administered at doses of up to 1g per day for up to six months has been shown to have no clinically significant effect on sperm count, motility or morphology.
4.7 Effects on ability to drive and use machinesThere have been no studies to investigate the effect of Zovirax 5% on driving performance or the ability to operate machinery. A detrimental effect on such activities cannot be predicted from the pharmacology of the active substance, but the adverse event profile should be borne in mind.
4.8 Undesirable effectsThe frequency categories associated with the adverse events below are estimates. For most events, suitable data for estimating incidence were not available. In addition, adverse events may vary in their incidence depending on the indication.
The following convention has been used for the classification of undesirable effects in terms of frequency: Very common > 1/10, common > 1/100 and < 1/10, uncommon > 1/1000 and < 1/100, rare > 1/10,000 and < 1/1000, very rare < 1/10,000
Blood and the lymphatic system disorders:
Very rare: Anaemia, leukopenia, thrombocytopenia.
Immune system disorders:
Rare: Anaphylaxis.
Psychiatric and nervous system disorders:
Common: Headache, dizziness.
Very rare: Agitation, confusion, tremor, ataxia, dysarthria, hallucinations, psychotic symptoms, convulsions, somnolence, encephalopathy, coma.
The above events are generally reversible and usually reported in patients with renal impairment or with other predisposing factors (see 4.4 Special Warnings and Precautions for Use).
Respiratory, thoracic and mediastinal disorders:
Rare: Dyspnoea.
Gastrointestinal disorders:
Common: Nausea, vomiting, diarrhoea, abdominal pains.
Hepato-biliary disorders:
Rare: Reversible rises in bilirubin and liver related enzymes.
Very rare: Hepatitis, jaundice.
Skin and subcutaneous tissue disorders:
Common: Pruritus, rashes (including photosensitivity).
Uncommon: Urticaria. Accelerated diffuse hair loss. Accelerated diffuse hair loss has been associated with a wide variety of disease processes and medicines, the relationship of the event to Zovirax 5% therapy is uncertain.
Rare: Angioedema.
Renal and urinary disorders:
Rare: Increases in blood urea and creatinine.
Very rare: Acute renal failure, renal pain.
Renal pain may be associated with renal failure and crystalluria.
General disorders and administration site conditions:
Common: fatigue, fever.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.
). Prolonged or repeated courses of aciclovir in severely immune-compromised individuals may result in the selection of virus strains with reduced sensitivity, which may not respond to continued aciclovir treatment.Hydration status: Care should be taken to maintain adequate hydration in patients receiving high oral doses of aciclovir.
The risk of renal impairment is increased by use with other nephrotoxic drugs.
The data currently available from clinical studies is not sufficient to conclude that treatment with aciclovir reduces the incidence of chickenpox-associated complications in immunocompetent patients.
4.5 Interaction with other medicinal products and other forms of interactionAciclovir is eliminated primarily unchanged in the urine via active renal tubular secretion. Any drugs administered concurrently that compete with this mechanism may increase aciclovir plasma concentrations. Probenecid and cimetidine increase the AUC of aciclovir by this mechanism, and reduce aciclovir renal clearance. Similarly increases in plasma AUCs of aciclovir and of the inactive metabolite of mycophenolate mofetil, an immunosuppresant agent used in transplant patients have been shown when the drugs are coadministered. However no dosage adjustment is necessary because of the wide therapeutic index of aciclovir.
An experimental study on five male subjects indicates that concomitant therapy with aciclovir increases AUC of totally administered theophylline with approximately 50%. It is recommended to measure plasma concentrations during concomitant therapy with aciclovir.
4.6 Fertility, pregnancy and lactationPregnancy:
The use of aciclovir should be considered only when the potential benefits outweigh the possibility of unknown risks.
A post-marketing aciclovir pregnancy registry has documented pregnancy outcomes in women exposed to any formulation of Zovirax 5%.
Breast-feeding:
Following oral administration of 200 mg Zovirax 5% five times a day, aciclovir has been detected in breast milk at concentrations ranging from 0.6 to 4.1 times the corresponding plasma levels. These levels would potentially expose nursing infants to aciclovir dosages of up to 0.3 mg/kg/day. Caution is therefore advised if aciclovir is to be administered to a nursing woman.
Fertility:
4.7 Effects on ability to drive and use machinesThere have been no studies to investigate the effect of aciclovir on driving performance or the ability to operate machinery. A detrimental effect on such activities cannot be predicted from the pharmacology of the active substance, but the adverse event profile should be borne in mind.
4.8 Undesirable effectsThe frequency categories associated with the adverse events below are estimates. For most events, suitable data for estimating incidence were not available. In addition, adverse events may vary in their incidence depending on the indication.
The following convention has been used for the classification of undesirable effects in terms of frequency:- Very common >1/10, common >1/100 and <1/10, uncommon >1/1000 and <1/100, rare >1/10,000 and <1/1000, very rare <1/10,000.
Blood and lymphatic system disorders:
Very rare: Anaemia, leukopenia, thrombocytopenia.
Immune system disorders:
Rare: Anaphylaxis.
Psychiatric and nervous system disorders:
Common: Headache, dizziness.
Very rare: Agitation, confusion, tremor, ataxia, dysarthria, hallucinations, psychotic symptoms, convulsions, somnolence, encephalopathy, coma.
The above events are generally reversible and usually reported in patients with renal impairment or with other predisposing factors (see 4.4 Special Warnings and Precautions for Use).
Respiratory, thoracic and mediastinal disorders:
Rare: Dyspnoea.
Gastrointestinal disorders:
Common: Nausea, vomiting, diarrhoea, abdominal pains.
Hepato-biliary disorders:
Rare: Reversible rises in bilirubin and liver related enzymes.
Very rare: Hepatitis, jaundice.
Skin and subcutaneous tissue disorders:
Common: Pruritus, rashes (including photosensitivity).
Uncommon: Urticaria. Accelerated diffuse hair loss. Accelerated diffuse hair loss has been associated with a wide variety of disease processes and medicines, the relationship of the event to aciclovir therapy is uncertain.
Rare: Angioedema.
Renal and urinary disorders:
Rare: Increases in blood urea and creatinine.
Very rare: Acute renal failure, renal pain.
Renal pain may be associated with renal failure and crystalluria.
General disorders and administration site conditions:
Common: Fatigue, fever.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at:.
Mutagenicity:
The results of a wide range of mutagenicity tests in vitro and in vivo indicate that Zovirax 5% is unlikely to pose a genetic risk to man.
Carcinogenicity:
Zovirax 5% was not found to be carcinogenic in long term studies in the rat and the mouse.
Teratogenicity:
Systemic administration of Zovirax 5% in internationally accepted standard tests did not produce embryotoxic or teratogenic effects in rats, rabbits or mice.
In a non-standard test in rats, foetal abnormalities were observed, but only following such high subcutaneous doses that maternal toxicity was produced. The clinical relevance of these findings is uncertain.
Fertility:
Largely reversible adverse effects on spermatogenesis in association with overall toxicity in rats and dogs have been reported only at doses of Zovirax 5% greatly in excess of those employed therapeutically. Two generation studies in mice did not reveal any effect of Zovirax 5% on fertility.
Mutagenicity:- The results of a wide range of mutagenicity tests in vitro and in vivo indicate that aciclovir is unlikely to pose a genetic risk to man.
Carcinogenicity:- Aciclovir was not found to be carcinogenic in long term studies in the rat and the mouse.
Teratogenicity:- Systemic administration of aciclovir in internationally accepted standard tests did not produce embryotoxic or teratogenic effects in rats, rabbits or mice.
In a non-standard test in rats, foetal abnormalities were observed, but only following such high subcutaneous doses that maternal toxicity was produced. The clinical relevance of these findings is uncertain.
Fertility:- Largely reversible adverse effects on spermatogenesis in association with overall toxicity in rats and dogs have been reported only at doses of aciclovir greatly in excess of those employed therapeutically. Two generation studies in mice did not reveal any effect of aciclovir on fertility.
Pharmacotherapeutic group: Direct acting antivirals, Nucleosides and nucleotides excl. reverse transcriptase inhibitors.
ATC code: J05AB01
Zovirax 5% is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against human herpes viruses, including herpes simplex virus (HSV) types I and II and varicella zoster virus (VZV).
The inhibitory activity of Zovirax 5% for HSV I, HSV II and VZV is highly selective. The enzyme thymidine kinase (TK) of normal, uninfected cells does not use Zovirax 5% effectively as a substrate, hence toxicity of mammalian host cells is low; however, TK encoded by HSV and VZV converts Zovirax 5% to Zovirax 5% monophosphate, a nucleoside analogue which is further converted to the diphosphate and finally to the triphosphate by cellular enzymes. Zovirax 5% triphosphate interferes with the viral DNA polymerase and inhibits viral DNA replication with resultant chain termination following its incorporation into the viral DNA.
Prolonged or repeated courses of Zovirax 5% in severely immuno-compromised individuals may result in the selection of virus strains with reduced sensitivity, which may not respond to continued Zovirax 5% treatment. Most of the clinical isolates with reduced sensitivity have been relatively deficient in viral TK, however, strains with altered viral TK or viral DNA polymerase have also been reported. In vitro exposure of HSV isolates to Zovirax 5% can also lead to the emergence of less sensitive strains. The relationship between the in vitro-determined sensitivity of HSV isolates and clinical response to Zovirax 5% therapy is not clear.
Pharmacotherapeutic group: Direct acting antivirals, Nucleosides and nucleotides excl. reverse transcriptase inhibitors
ATC code: J05AB01.
Aciclovir is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against human herpes viruses, including herpes simplex virus (HSV) types I and II and varicella zoster virus (VZV).
The inhibitory activity of aciclovir for HSV I, HSV II and VZV is highly selective. The enzyme thymidine kinase (TK) of normal, uninfected cells does not use aciclovir effectively as a substrate, hence toxicity of mammalian host cells is low; however, TK encoded by HSV and VZV converts aciclovir to aciclovir monophosphate, a nucleoside analogue which is further converted to the diphosphate and finally to the triphosphate by cellular enzymes. Aciclovir triphosphate interferes with the viral DNA polymerase and inhibits viral DNA replication with resultant chain termination following its incorporation into the viral DNA.
Prolonged or repeated courses of aciclovir in severely immune-compromised individuals may result in the selection of virus strains with reduced sensitivity, which may not respond to continued aciclovir treatment. Most of the clinical isolates with reduced sensitivity have been relatively deficient in viral TK, however, strains with altered viral TK or viral DNA polymerase have also been reported. In vitro exposure of HSV isolates to aciclovir can also lead to the emergence of less sensitive strains. The relationship between the in vitro determined sensitivity of HSV isolates and clinical response to aciclovir therapy is not clear.
Zovirax 5% is only partially absorbed from the gut. Mean steady state peak plasma concentrations (Cssmax) following doses of 200 mg administered four-hourly were 3.1 microMol (0.7 micrograms/ml) and equivalent trough plasma levels (Cssmin) were 1.8 microMol (0.4 micrograms/ml). Corresponding Cssmax levels following doses of 400 mg and 800 mg administered four-hourly were 5.3 microMol (1.2 micrograms/ml) and 8 microMol (1.8 micrograms/ml) respectively and equivalent Cssmin levels were 2.7 microMol (0.6 micrograms/ml) and 4 microMol (0.9 micrograms/ml).
In adults the terminal plasma half-life of Zovirax 5% after administration of intravenous Zovirax 5% is about 2.9 hours. Most of the drug is excreted unchanged by the kidney. Renal clearance of Zovirax 5% is substantially greater than creatinine clearance, indicating that tubular secretion, in addition to glomerular filtration contributes to the renal elimination of the drug. 9-carboxymethoxymethylguanine is the only significant metabolite of Zovirax 5%, and accounts for approximately 10 - 15% of the administered dose recovered from the urine. When Zovirax 5% is given one hour after 1 gram of probenecid the terminal half-life and the area under the plasma concentration time curve is extended by 18% and 40% respectively.
In adults, mean steady state peak plasma concentrations (Cssmax) following a one hour infusion of 2.5 mg/kg, 5 mg/kg and 10 mg/kg were 22.7 microMol (5.1 micrograms/ml), 43.6 microMol (9.8 micrograms/ml) and 92 microMol (20.7 micrograms/ml), respectively. The corresponding trough levels (Cssmin) 7 hours later were 2.2 microMol (0.5 micrograms/ml), 3.1 microMol (0.7 micrograms/ml), and 10.2 microMol (2.3 micrograms/ml), respectively.
In children over 1 year of age similar mean peak (Cssmax) and trough (Cssmin) levels were observed when a dose of 250 mg/m2 was substituted for 5 mg/kg and a dose of 500 mg/m2 was substituted for 10 mg/kg. In neonates and young infants (0 to 3 months of age) treated with doses of 10 mg/kg administered by infusion over a one-hour period every 8 hours the Cssmax was found to be 61.2 microMol (13.8 micrograms/ml) and Cssmin to be 10.1 microMol (2.3 micrograms/ml). The terminal plasma half-life in these patients was 3.8 hours. A separate group of neonates treated with 15 mg/kg every 8 hours showed approximate dose proportional increases, with a Cmax of 83.5 micromolar (18.8 microgram/ml) and Cmin of 14.1 micromolar (3.2 microgram/ml).
In the elderly, total body clearance falls with increasing age associated with decreases in creatinine clearance although there is little change in the terminal plasma half-life.
In patients with chronic renal failure the mean terminal half-life was found to be 19.5 hours. The mean Zovirax 5% half-life during haemodialysis was 5.7 hours. Plasma Zovirax 5% levels dropped approximately 60% during dialysis.
Cerebrospinal fluid levels are approximately 50% of corresponding plasma levels. Plasma protein binding is relatively low (9 to 33%) and drug interactions involving binding site displacement are not anticipated.
Aciclovir is only partially absorbed from the gut. Mean steady state peak plasma concentrations (Cssmax) following doses of 200 mg administered four-hourly were 3.1 microMol (0.7 micrograms/ml) and equivalent trough plasma levels (Cssmin) were 1.8 microMol (0.4 micrograms/ml). Corresponding Cssmax levels following doses of 400 mg and 800 mg administered four-hourly were 5.3 microMol (1.2 micrograms/ml) and 8 microMol (1.8 micrograms/ml) respectively and equivalent Cssmin levels were 2.7 microMol (0.6 micrograms/ml) and 4 microMol (0.9 micrograms/ml).
In adults the terminal plasma half-life of aciclovir after administrations of intravenous aciclovir is about 2.9 hours. Most of the drug is excreted unchanged by the kidney. Renal clearance of aciclovir is substantially greater than creatinine clearance, indicating that tubular secretion, in addition to glomerular filtration contributes to the renal elimination of the drug. 9-carboxymethoxymethylguanine is the only significant metabolite of aciclovir, and accounts for approximately 10 - 15% of the administered dose recovered from the urine. When aciclovir is given one hour after 1 gram of probenecid the terminal half-life and the area under the plasma concentration time curve is extended by 18% and 40% respectively.
In adults, mean steady state peak plasma concentrations (Cssmax) following a one hour infusion of 2.5 mg/kg, 5 mg/kg and 10 mg/kg were 22.7 microMol (5.1 micrograms/ml), 43.6 microMol (9.8 micrograms/ml) and 92 microMol (20.7 micrograms/ml), respectively. The corresponding trough levels (Cssmin) 7 hours later were 2.2 microMol (0.5 micrograms/ml), 3.1 microMol (0.7 micrograms/ml), and 10.2 microMol (2.3 micrograms/ml), respectively.
In children over 1 year of age similar peak (Cssmax) and trough (Cssmin) levels were observed when a dose of 250 mg/m2 was substituted for 5 mg/kg and a dose of 500 mg/m2 was substituted for 10 mg/kg. In neonates and young infants (0 to 3 months of age) treated with doses of 10 mg/kg administered by infusion over a one-hour period every 8 hours the Cssmax was found to be 61.2 microMol (13.8 micrograms/ml) and Cssmin to be 10.1 microMol (2.3 micrograms/ml). The terminal plasma half-life in these patients was 3.8 hours. A separate group of neonates treated with 15 mg/kg every 8 hours showed approximate dose proportional increases, with a Cmax of 83.5 micromolar (18.8 microgram/ml) and Cmin of 14.1 micromolar (3.2 microgram/ml). In the elderly, total body clearance falls with increasing age associated with decreases in creatinine clearance although there is little change in the terminal plasma half-life.
In patients with chronic renal failure the mean terminal half-life was found to be 19.5 hours. The mean aciclovir half-life during haemodialysis was 5.7 hours. Plasma aciclovir levels dropped approximately 60% during dialysis.
Cerebrospinal fluid levels are approximately 50% of corresponding plasma levels. Plasma protein binding is relatively low (9 to 33%) and drug interactions involving binding site displacement are not anticipated.
Use in patients with renal impairment and in elderly patients:
Zovirax 5% is eliminated by renal clearance, therefore the dose must be adjusted in patients with renal impairment (see 4.2 Posology and Method of Administration).
Elderly patients are likely to have reduced renal function and therefore the need for dose adjustment must be considered in this group of patients. Both elderly patients and patients with renal impairment are at increased risk of developing neurological side effects and should be closely monitored for evidence of these effects. In the reported cases, these reactions were generally reversible on discontinuation of treatment (see 4.8 Undesirable Effects).
Prolonged or repeated courses of Zovirax 5% in severely immune-compromised individuals may result in the selection of virus strains with reduced sensitivity, which may not respond to continued Zovirax 5% treatment.
Hydration status: Care should be taken to maintain adequate hydration in patients receiving high oral doses of Zovirax 5%.
The risk of renal impairment is increased by use with other nephrotoxic drugs.
The data currently available from clinical studies is not sufficient to conclude that treatment with Zovirax 5% reduces the incidence of chickenpox-associated complications in immunocompetent patients.
Paediatric population:
Oral Zovirax 5% should be used in paediatric population mainly for the treatment of non-severe skin and mucosa HSV infections. For the treatment of neonatal HSV and severe HSV infections in immunocompromised children IV Zovirax 5% should be used.
Use in patients with renal impairment and in elderly patients:
Aciclovir is eliminated by renal clearance, therefore the dose must be adjusted in patients with renal impairment (see 4.2 Posology and Method of Administration). Elderly patients are likely to have reduced renal function and therefore the need for dose adjustment must be considered in this group of patients. Both elderly patients and patients with renal impairment are at increased risk of developing neurological side effects and should be closely monitored for evidence of these effects. In the reported cases, these reactions were generally reversible on discontinuation of treatment (see 4.8 Undesirable Effects). Prolonged or repeated courses of aciclovir in severely immune-compromised individuals may result in the selection of virus strains with reduced sensitivity, which may not respond to continued aciclovir treatment.
Hydration status: Care should be taken to maintain adequate hydration in patients receiving high oral doses of aciclovir.
The risk of renal impairment is increased by use with other nephrotoxic drugs.
The data currently available from clinical studies is not sufficient to conclude that treatment with aciclovir reduces the incidence of chickenpox-associated complications in immunocompetent patients.
There have been no studies to investigate the effect of Zovirax 5% on driving performance or the ability to operate machinery. A detrimental effect on such activities cannot be predicted from the pharmacology of the active substance, but the adverse event profile should be borne in mind.
There have been no studies to investigate the effect of aciclovir on driving performance or the ability to operate machinery. A detrimental effect on such activities cannot be predicted from the pharmacology of the active substance, but the adverse event profile should be borne in mind.
Not applicable.
No special requirements.
Any unused medicinal product or waste material should be disposed of in accordance with local requirements.
Administrative Data
