BNF for Children 2011-2012

BNFC 2011–2012 4.8 Antiepileptics 215ache. If an injection is unsuitable, sumatriptan nasalspray or zolmitriptan nasal spray may be used. Treatmentshould be initiated by a specialist. Alternatively,100% oxygen at a rate of 10–15 litres/minute for 10–20minutes is useful in aborting an attack.The other trigeminal autonomic cephalalgias, paroxysmalhemicrania (sensitive to indometacin), and shortlastingunilateral neuralgiform headache attacks withconjunctival injection and tearing, are seen rarely andare best managed by a specialist.4.8 Antiepileptics4.8.1 Control of the epilepsies4.8.2 Drugs used in status epilepticus4.8.3 Febrile convulsionsof adverse effects and drug interactions (see below). Ifcombination therapy does not bring about worthwhilebenefits, revert to the regimen (monotherapy or combinationtherapy) that provided the best balance betweentolerability and efficacy.Interactions Interactions between antiepileptics arecomplex and may increase toxicity without a correspondingincrease in antiepileptic effect. Interactionsare usually caused by hepatic enzyme induction orhepatic enzyme inhibition; displacement from proteinbinding sites is not usually a problem. These interactionsare highly variable and unpredictable.For interactions of antiepileptic drugs, see Appendix 1;for advice on hormonal contraception and enzymeinducingdrugs, see section 7.3.1 and section 7.3.2.Significant interactions that occur between antiepilepticsand that may affect dosing requirements are asfollows:Note Check under each drug for possible interactions whentwo or more antiepileptic drugs are used4.8.1 Control of the epilepsiesThe decision about when to start treatment with anantiepileptic drug and the choice of medication dependson frequency and type of seizures, neurological findings,the identification of an epilepsy syndrome, and thewishes of the child and carers. For the majority ofchildren, epilepsy is controlled with a single antiepilepticdrug.The object of treatment is to prevent the occurrence ofseizures by maintaining an effective dose of one or moreantiepileptic drugs. Careful adjustment of doses isnecessary, starting with low doses and increasing graduallyuntil seizures are controlled or there are significantadverse effects.When choosing an antiepileptic drug to use, the seizuretype, epilepsy syndrome, concomitant medication, comorbidity,age, and sex should be taken into account.For women of child-bearing age, see Pregnancy, p. 216and Breast-feeding, p. 217.The frequency of administration is often determined bythe plasma-drug half-life, and should be kept as low aspossible to encourage better adherance. Most antiepileptics,when used in usual dosage, can be giventwice daily. Lamotrigine, phenobarbital and phenytoin,which have long half-lives, can be given as a daily doseat bedtime. However, with large doses, some antiepilepticsmay need to be given 3 times daily to avoid adverseeffects associated with high peak plasma-drug concentrations.Young children metabolise some antiepilepticsmore rapidly than adults and therefore may requiremore frequent doses and a higher amount per kilogrambody-weight.Management When monotherapy with a first-lineantiepileptic drug has failed, monotherapy with a seconddrug should be tried; the diagnosis should bechecked before starting an alternative drug if the firstdrug showed lack of efficacy. The change from oneantiepileptic drug to another should be cautious, slowlywithdrawing the first drug only when the new regimenhas been established. Combination therapy with two ormore antiepileptic drugs may be necessary, but theconcurrent use of antiepileptic drugs increases the riskCarbamazepineoften lowers plasma concentration of clobazam, clonazepam,lamotrigine, phenytoin (but may also raiseplasma-phenytoin concentration), tiagabine, topiramate,valproate, and an active metabolite of oxcarbazepinesometimes lowers plasma concentration of ethosuximide,primidone (but tendency for correspondingincrease in plasma-phenobarbital concentration), andrufinamidesometimes raises plasma concentration of phenobarbitaland primidone-derived phenobarbitalEthosuximidesometimes raises plasma concentration of phenytoinLamotriginesometimes raises plasma concentration of an activemetabolite of carbamazepine (but evidence is conflicting)Oxcarbazepinesometimes lowers plasma concentration of carbamazepine(but may raise plasma concentration of an activemetabolite of carbamazepine)sometimes raises plasma concentration of phenytoinoften raises plasma concentration of phenobarbital andprimidone-derived phenobarbitalPhenobarbital or Primidoneoften lowers plasma concentration of clonazepam, lamotrigine,phenytoin (but may also raise plasma-phenytoinconcentration), tiagabine, valproate, and an activemetabolite of oxcarbazepinesometimes lowers plasma concentration of ethosuximide,rufinamide, and topiramatePhenytoinoften lowers plasma concentration of clonazepam,carbamazepine, lamotrigine, tiagabine, topiramate, valproate,and an active metabolite of oxcarbazepineoften raises plasma concentration of phenobarbital andprimidone-derived phenobarbitalsometimes lowers plasma concentration of ethosuximide,primidone (by increasing conversion to phenobarbital),and rufinamide4 Central nervous system