Thesis (PhD)--Stellenbosch University, 2013. / Bibliography / ENGLISH ABSTRACT: Introduction:
Lipoatrophy is a common adverse effect of stavudine and this effect is strongly dose-dependent. Stavudine remains the most commonly used paediatric antiretroviral drug in sub-Saharan Africa, yet when the current study began in 2009, the prevalence and severity of lipoatrophy in children on antiretroviral therapy in sub-Saharan Africa had never been studied. The development of lipoatrophy may have serious and far-reaching consequences for patients and their families. The off-label stavudine dosing method, prescribed to children whose caregivers do not have access to a refrigerator, in which the contents of an adult capsule is mixed into tap water, has potential for over-dosing or under-dosing. In addition, children on stavudine continue to be exposed to a disproportionately high dose out of line with the reduced adult dose.
Aims:
1. a) To investigate the prevalence and risk factors for lipoatrophy in HIV-infected children in Southern Africa
b) To identify a simple anthropometric screening tool to detect early lipoatrophy in children
2. To validate the off-label stavudine dosing method prescribed to children whose caregivers do not have access to a refrigerator, with a view to reducing the recommended dose and thereby the side-effects.
Methods:
1. a) We recruited pre-pubertal children on antiretroviral therapy from a family HIV clinic in our facility. Lipoatrophy was identified by two experienced paediatric HIV clinicians using a standardized grading scale. A dietician performed dietary assessment and anthropometric
measurements. Previous antiretroviral exposures were recorded. A subset of recruits received Dual-Energy X-ray Absorbtiometry scanning.
b) Anthropometric measurements in children with and without lipoatrophy were compared using multivariate linear regression adjusting for age and gender. The most discerning anthropometric variables underwent Receiver Operating Characteristic curve analysis to identify the most appropriate diagnostic cut-off.
2. a) Accuracy of the standard off-label stavudine dosing method was investigated using high-performance liquid chromatography to recover active drug from solutions made up using the prescribed method. This was compared to the stated drug content of the capsules.
b) Bioavailability was investigated by performing a randomized crossover pharmacokinetic study wherein healthy HIV-seronegative adult volunteers received one of two generic stavudine capsule formulations, either intact or mixed in water using the prescribed method. Plasma stavudine concentrations were assayed by liquid chromatography tandem mass spectrometry.
Results:
1. a) Prevalence of lipoatrophy was 36%, and incidence was 12% per person-year. Adjusted odds ratio for developing lipoatrophy was 1.9 (CI: 1.3–2.9) for each additional year of accumulated exposure to standard-dose stavudine.
b) Baseline biceps skin-fold thickness correlated well with maximum lipoatrophy grading score at any site, giving a partial correlation coefficient of 0.33 (p=0.0006), and a receiver operating characteristic area-under-curve value of 0.75 (CI: 0.64 – 0.84). Biceps skin-fold thickness <5mm at baseline had a sensitivity of 89% (CI: 67–100%) and a negative predictive value of 97% (CI: 91–100%) for predicting which children would go on to develop lipoatrophy by 15 month follow-up. Specificity was 60% (CI: 46–75%) and positive predictive value was 32% (CI: 14–50%).
2. a) Recovery of active drug from solution was 97.1%, 97.4% and 93.8% for the proprietary and two generic formulations respectively.
b) Pharmacokinetic parameters of the off-label dosing method were well within the target range of intact capsule dosing for both generics.
Conclusions:
1. a) The prevalence and incidence of lipoatrophy in pre-pubertal children on antiretroviral therapy in South Africa is high. Cumulative exposure to standard-dose stavudine was the greatest risk factor for lipoatrophy.
b) Biceps skin-fold thickness provided reasonable sensitivity and specificity to detect and predict lipoatrophy in pre-pubertal children on antiretroviral therapy.
2. The off-label dosing method for stavudine prescribed to children whose caregivers do not have access to a refrigerator is reasonably accurate and is bioequivalent to intact capsule administration. / AFRIKAANSE OPSOMMING: Inleiding:
Lipoatrofie is 'n algemene nadelige uitwerking van stavudien en hierdie effek is sterk dosis-afhanklike. Stavudien bly die mees algemeen gebruikte paediatriese antiretrovirale medikasie in sub-Sahara Afrika, maar toe ons studie begin het, was lipoatrofie in kinders op antiretrovirale terapie in sub-Sahara Afrika nog nooit voorheen bestudeer nie. Die ontwikkeling van lipoatrofie kan ernstige en verreikende gevolge vir die pasiënt en hul familie hê. Die af-etiket stavudien dosering metode voorgeskryf aan kinders wie se versorgers nie toegang tot 'n yskas het nie het 'n aansienlike potensiäal vir oor-dosering of onder-dosering. Daarbenewens, is kinders op stavudien blootgestel aan 'n disproporsionele hoë dosis uit-pas met die verminderde volwasse dosis.
Doelwitte:
1. a) Om ondersoek in te stel na die voorkoms en risiko faktore vir lipoatrofie in MIV-geïnfekteerde kinders in Suid Afrika
b) Om 'n eenvoudige antropometriese instrument te identifiseer om vroeë lipoatrofie op te spoor in kinders op antiretrovirale medikasie
2. Om die af-etiket stavudien dosering metode wat voorgeskryf is aan kinders wie se versorgers nie toegang tot 'n yskas het nie te valideer, met 'n oog op die vermindering van die aanbevole dosis
Metodes:
1. a) Ons het 'n groep van onder-puberteitsjarige kinders op antiretrovirale terapie gewerf uit 'n familie MIV kliniek in ons fasiliteit. Lipoatrofie is geïdentifiseer deur twee ervare MIV pediaters deur gebruik van 'n gestandaardiseerde gradering skaal. 'n Diëetkundige het diëet assessering en
antropometriese metings uitgevoer. Vorige antiretrovirale blootstellings is aangeteken. In 'n subset was Dual-energie X-straal Absorbtiometry (DXA) skandering uitgevoer.
b) Antropometriese metings in kinders met en sonder lipoatrofie is vergelyk met behulp van meerveranderlike lineêre regressie aangepas vir ouderdom en geslag. Die mees kieskeurige antropometriese veranderlikes het Receiver Operating Curve analise ondergaan om die mees geskikte diagnostiese afgesnypunt te identifiseer.
2. a) Akkuraatheid is ondersoek deur gebruik te maak van hoë werkverrigting vloeistofchromatografie om aktiewe medikasie vanuit oplossings te herstel, wat gemeng is soos aangedui deur die voorgeskrewe af-etiket dosering metode.
b) Biobeskikbaarheid is ondersoek deur die uitvoering van 'n ewekansige oorgesteekde farmakokinetiese studie waarin gesonde MIV- negatiewe volwasse vrywilligers een van twee generiese stavudien kapsule formulerings ontvang het, óf heel of in water gemeng soos aangedui deur die voorgeskrewe af-etiket dosering metode. Plasma stavudien konsentrasies is gemeet deur vloeistofchromatografie tandem massaspektrometrie.
Uitslae:
1. a) Voorkoms van lipoatrofie was 36%, en insidensie was 12% per persoon-jaar. Aangepaste Odds ratio vir die ontwikkeling van lipoatrofie was 1,9 (CI: 1,3-2,9) vir elke addisionele jaar van opgehoopte blootstelling aan standaard dosis stavudien.
b) Biceps vel-vou dikte <5mm het 'n sensitiwiteit van 89% (CI: 83-96%) en 'n negatiewe voorspellende waarde van 90% (CI: 84-96%) vir die opsporing en voorspelling van lipoatrofie.
2. a) Herwinning van aktiewe medikasie uit oplossings was 97,1%, 97,4% en 93,8% vir die oorspronklike en twee generiese formulerings onderskeidelik.
b) Farmakokinetiese parameters van die af-etiket dosering metode was wel binne die teikenband van ongeskonde kapsule dosering vir beide generiese formulerings.
Gevolgtrekkings:
1. a) Die voorkoms van lipoatrofie in onder-puberteitsjarige kinders op antiretrovirale terapie in Suid-Afrika is hoog. Die bedrag stavudien waaraan kinders blootgestel is moet hersien word. Die standaard stavudien dosis vir kinders moet herge-evalueer word.
b) Biceps vel-vou dikte het redelike goeie sensitiwiteit en spesifisiteit om lipoatrofie op te spoor en te voorspel.
2. Die af-etiket dosering metode vir stavudien voorgeskryf aan kinders wie se versorgers nie toegang tot 'n yskas het nie is redelik akkuraat en is bio-ekwivalent aan ongeskonde kapsule administrasie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/79864 |
| Date | 03 1900 |
| Creators | Innes, Steven Eugene Vere |
| Contributors | Cotton, Mark Fredric, Rosenkranz, Bernd, Rabie, Helena, Zollner, Ekkehard Werner, Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Paediatrics and Child Health. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 105 p. : ill. |
| Rights | Stellenbosch University |
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