Important aspects of prescribing information relevant to primary healthcare are covered in this section specifically for the drugs recommended in this CKS topic. For further information on contraindications, cautions, drug interactions, and adverse effects, see the electronic Medicines Compendium (eMC) (http://emc.medicines.org.uk), or the British National Formulary (BNF) (www.bnf.org).

• Paracetamol and ibuprofen are well tolerated when used for short periods [BNF 54, 2007]:
• Both paracetamol and ibuprofen are licensed for the relief of pain and fever from 3 months of age:
• Both drugs are recommended for the management of feverish illnesses in children younger than 5 years of age [NICE, 2007a].
• For use in pregnancy or breastfeeding, see Choice in pregnancy or breastfeeding
• Seek specialist advice before prescribing to neonates younger than 4 weeks of age given the high risk of complications in this age group.
• Both paracetamol and ibuprofen are not licensed for use under 4 weeks of age.
• As with other nonsteroidal anti-inflammatory drugs (NSAIDs), ibuprofen may worsen or precipitate gastrointestinal haemorrhage, asthma, hypertension, renal impairment, or cardiac failure. Avoid ibuprofen if there is a history of peptic ulcers. Paracetamol is often a safer option in older people.
• Paracetamol and ibuprofen rarely cause adverse effects when used in the short term [BNF 54, 2007]:
• Paracetamol has no notable adverse effects when used at the correct dosage.
• Ibuprofen may occasionally cause exacerbation of asthma and gastrointestinal adverse effects, such as discomfort, nausea, and diarrhoea.
• There are concerns that use of NSAIDs in children with varicella is associated with an increased risk of necrotizing soft-tissue infections and infections with invasive group A beta-haemolytic streptococci [Heininger and Seward, 2006]:
• Evidence from two small case-control studies are conflicting [Lesko and Mitchell, 1995; Zerr et al, 1999].
• Although the association cannot be ruled out with certainty, evidence is insufficient to advise that ibuprofen (or other NSAIDs) be avoided in children with chickenpox.

• Paracetamol is the analgesic and antipyretic of choice because it can be used at the usual dosage and at any stage of pregnancy and during breastfeeding.
• Ibuprofen may be considered for use in breastfeeding and pregnant women, but it should not used beyond 27 weeks of gestation because of the increased risk of constriction of the ductus arteriosus.
• Constriction of ductus arteriosus:
• Constriction is related to gestational age; it is rare before week 27, but its incidence increases with advancing gestational age to 50–70% at 32 weeks and up to 100% with exposure from week 34 onwards.
• The effect appears not to be dose dependent.
• If use of ibuprofen is unavoidable, fetal circulation should be monitored regularly (once or twice weekly) with Doppler sonography, and medication use should be stopped as soon as signs of ductal constriction appear.
• Breastfeeding:
• Ibuprofen was not detected in breast milk following administration of 800–1600 mg daily in two small studies. No adverse effects on breastfed children were reported in both studies and also in a prospective study covering 21 mother-child pairs.

[Schaefer et al, 2007]

• Aciclovir is the preferred antiviral drug for the treatment of chickenpox in adults.
• If aciclovir is indicated, a dose of 800 mg five times daily for seven days should be prescribed [ABPI Medicines Compendium, 2007].
• Treatment should begin within 24 hours of the onset of the rash [ABPI Medicines Compendium, 2007].

• Aciclovir is licensed for the treatment of chickenpox [ABPI Medicines Compendium, 2007] and has been recommended for the treatment of chickenpox in immunocompetent adults [Wilkins et al, 1998].
• A review by BMJ Clinical Evidence identified one randomized controlled trial (n = 148 adults) in a systematic review which found aciclovir (800 mg 5 times daily) given within 24 hours of the onset of rash reduced the maximum number of lesions (p < 0.01) and the time to full crusting of lesions (p = 0.001) compared to placebo [Swingler, 2007].
• Other antivirals:
• These are not recommended as they are not licensed for the treatment of chickenpox.
• A review by BMJ Clinical Evidence found no systematic review or randomized controlled trials of famciclovir or valaciclovir for the treatment of chickenpox in healthy people [Swingler, 2007].

• Aciclovir is the preferred antiviral drug because of its long-term safety data in pregnant women.
• A dose of 800 mg five times daily for seven days should be prescribed on the advice of a specialist.
• Informed consent should be obtained because aciclovir is unlicensed for use in pregnancy.

• The recommendation to prescribe aciclovir is based on guidance issued by the British Society for the Study of Infection, Public Health Laboratory Services, Royal College of Obstetricians and Gynaecologists, and Health Protection Agency [Ogilvie, 1998; Morgan-Capner et al, 2002; HPA, 2007b; RCOG, 2007].
• Dose of aciclovir:
• The recommended dose of aciclovir for use in pregnancy is based on guidance issued by the British Society for the Study of Infection and Public Health Laboratory Service [Nathwani et al, 1998; Morgan-Capner et al, 2002].
• This aciclovir dose is the same as that used for the treatment of varicella infection in an immunocompetent adult [ABPI Medicines Compendium, 2007; BNF 54, 2007].
• Aciclovir is preferred over valaciclovir because there are good long-term safety data for aciclovir in pregnant women:
• Data from the International Aciclovir Pregnancy Registry (1984–1999) found that in the 1234 pregnancies followed, the observed rates and types of birth defects for pregnancies exposed to aciclovir did not differ significantly from those in the general population [Stone et al, 2004].
• Pregnancy outcomes from 111 prospectively registered pregnancies in the Valaciclovir Pregnancy Registry found no apparent adverse outcomes. However, these data, together with those from other small studies, provide insufficient information for a risk evaluation. Consequently, the use of valaciclovir is not recommended during pregnancy because of insufficient data [Schaefer et al, 2007].
• Other reasons for preferring aciclovir:
• Unlike valaciclovir, aciclovir is licensed for the treatment of varicella infections.
• It is also less expensive than valaciclovir.

• Advise people receiving high doses of aciclovir to maintain adequate hydration. This is particularly important if the person is elderly or has renal impairment.
• Aciclovir is excreted via the kidneys. Adequate hydration minimizes the risk of renal damage with high dose aciclovir treatment.
• Remind the person to take the aciclovir regularly at 4-hourly intervals during the day (with an 8 hour gap overnight):
• Suggested times are 7 a.m., 11 a.m., 3 p.m., 7 p.m., and 11 p.m.
• If these times are not suitable, aciclovir can be taken at different times, as long as the doses are spaced at least 4 hours apart.
• Reassure the person that oral aciclovir is generally well tolerated:
• Gastrointestinal symptoms (e.g. nausea, vomiting, diarrhoea, and abdominal pain) and skin rashes (including photosensitivity and urticaria) are the most common adverse effects.

[Ogilvie, 1998; Heininger and Seward, 2006; ABPI Medicines Compendium, 2007; BNF 54, 2007]