ORIGINAL STUDIES Adherence and Acceptability of Once Daily Lamivudine and Abacavir in Human Immunodeficiency Virus Type-1 Infected Children Marthe LePrevost, MSc,* Hannah Green, MSc,† Jacquie Flynn, BSc,‡ Stephen Head, MA,§ Margaret Clapson, BSc,‡ Hermione Lyall, MD,§ Vas Novelli, MBCHB,‡ Laura Farrelly, BSc,† A. Sarah Walker, PhD,† David M. Burger, PhD,¶ and Diana M. Gibb, MD ,† , on Behalf of the Pediatric European Network for the Treatment of AIDS 13 Study Group Background: Data on adherence to and acceptability of once daily lamivudine and abacavir are few. Methods: Twenty-four U.K. human immunodeficiency virus type-1 infected children 2–13 years of age participated in the Pediatric Euro- pean Network for the Treatment of AIDS (PENTA) 13 single arm, open label pharmacokinetic study of twice (every 12 hours) versus once (every 24 hours) daily lamivudine and abacavir. Caregivers were asked to complete an adherence questionnaire at screening, week 0 (switch once daily to twice daily) and weeks 4, 12 and 24. Acceptability was also assessed at screening and week 24. Results: Fifteen children were taking lamivudine and abacavir as part of their regimens, 8 lamivudine only and 1 abacavir only. After switching to lamivudine/abacavir every 24 hours, 7 (29%) received once daily regimens for all drugs. Twenty-three (96%) caregivers thought that switching to once daily lamivudine/abacavir would make things a lot/a little easier for their child: 17 (71%) thought it was actually easier after switching. Six mothers with children taking a mixture of twice/once daily drugs changed their mind, whereas all mothers of children on once daily regimens agreed that it was a lot easier. Nonadherence (missing doses in the last 3 days) was reported for 8 of 118 (7%) completed questionnaires; missed doses were reported for every drug in the regimen with reasons such as “not at home,” “forgot” or “routine different from normal.” However, viral loads in all these children remained 100 copies/mL. Conclusion: Adherence to once daily abacavir/lamivudine was good with no evidence of an association between nonadherence and virologic rebound. Acceptability of once daily drugs was best when the whole regimen was dosed once daily. Key Words: antiretroviral, adherence, once daily dosing, lamivudine, abacavir (Pediatr Infect Dis J 2006;25: 533–537) F or adults and children with access to effective antiretro- viral therapy (ART), human immunodeficiency virus (HIV) care has changed greatly, with reductions in mortality and morbidity and improvements in quality of life. 1–3 The major challenge now being faced is achieving near perfect adherence to ART (95% or greater) required for viral sup- pression over long periods of time. 4 Medication regimen (number of pills, schedule, life-style and dietary restrictions), patient factors (health beliefs, social support), and patient- health care provider relationship are critical factors that have been found to influence adherence in adult studies. 2,5– 8 Children and families with HIV also face unique adher- ence problems as a result of the dependency of the children on their caregivers for their medication. The dynamics of the caregiver-child relationship, palatability and the children’s un- derstanding of their illness are all crucial aspects for adherence in children that may not be relevant to adherence in adults. 2,7–12 Studies in adults suggest patient preference for compact once daily regimens, providing that efficacy and tolerability are similar to twice daily regimens, 14 –16 and an increasing number of antiretrovirals approved for once daily use in adults facilitate development of simpler combination regimen schedules. How- ever, for children, pediatric pharmacokinetic data lag behind those of their adult counterparts, 17 resulting in most drugs still being used in twice daily schedules. Here we report on findings from adherence and acceptability questionnaires completed by caregivers of children participating in a study comparing the pharmacokinetics (PK) of twice daily versus once daily lamivu- dine and abacavir as part of a 3- or 4-drug ART combination. This Pediatric European Network for the Treatment of AIDS (PENTA) study found the PK of once daily lamivudine and abacavir were not inferior to twice daily. 18 METHODS Study Design. PENTA 13 was a single sequence, 2-period, cross-over, open label PK study of twice daily (every 12 Accepted for publication January 19, 2006. From the *Family Clinic, North West London NHS Trust, the †Medical Research Council Clinical Trials Unit, the ‡Infectious Disease Unit, ABC Family Clinic, Great Ormond Street Hospital for Sick Children, and the §Infectious Diseases Unit, Family Clinic, St. Mary’s Hospital, London, United Kingdom; and Radboud University Medical Centre Nijmegen and ¶Nijmegen University Center for Infectious Diseases, Nijmegen, the Netherlands. Supported by GlaxoSmithKline. Address for correspondence: Dr D. M. Gibb, MRC Clinical Trials Unit, 222 Euston Road, London NW1 2DA, United Kingdom. E-mail: Di.Gibb@ ctu.mrc.ac.uk. Copyright © 2006 by Lippincott Williams & Wilkins ISSN: 0891-3668/06/2506-0533 DOI: 10.1097/01.inf.0000222415.40563.d4 The Pediatric Infectious Disease Journal • Volume 25, Number 6, June 2006 533