Role of lipid-lowering pharmacotherapy in children

Role of colesevelam in managing heterozygous familial hypercholesterolemia in adolescents and children

BACKGROUND

Colesevelam hydrochloride is a synthetic, nonsystemically absorbed polymer that functions as a bile acid sequestrant for the treatment of hypercholesterolemia. Recently, colesevelam was investigated for the treatment of heterozygous familial hypercholesterolemia (HeFH) in the pediatric/adolescent population aged 10-17 years.

OBJECTIVE

The purpose of this article is to review the disease state of HeFH in children and adolescents, review the pharmacologic mechanism of action, kinetics, and safety profile of colesevelam, analyze the results of a recent clinical trial of colesevelam in the pediatric/adolescent HeFH population, and discuss the role of colesevelam as a viable treatment option for HeFH.

METHODS

A literature search using Medline (1966-03 May 2010), PubMed (1950-03 May 2010), Science Direct (1994-03 May 2010), and International Pharmaceutical Abstracts (2004-2010) was performed using the search term colesevelam. English language, original research, and review articles were examined, and citations from these articles were also assessed. The manufacturer's prescribing information and the Food and Drug Administration review of the new drug application for the powder formulation were also examined.

RESULTS

A 32-week trial was performed investigating the efficacy of colesevelam as monotherapy or combination therapy with a stable statin regimen. Upon completion of the trial, significant benefits were found in regard to the treatment of HeFH and the lowering of low-density lipoprotein cholesterol, total cholesterol, and other secondary measures. Safety and tolerability were also examined throughout the duration of the clinical trial, with adverse drug reactions considered mild in severity.

CONCLUSION

Colesevelam has been shown to reduce low-density lipoprotein cholesterol levels significantly in pediatric/adolescent patients with HeFH, while maintaining a mild side effect profile. Although further research would be beneficial for long-term effects in this population, colesevelam should be considered when developing a treatment regimen for HeFH in the pediatric/adolescent population.

Inhibition of the intestinal absorption of bile acids using cationic derivatives: mechanism and repercussions

To pharmacologically interrupt bile acid enterohepatic circulation, two compounds named BAPA-3 and BAPA-6, with a steroid structure and 1 or 2 positive charges, were obtained by conjugation of N-(3-aminopropyl)-1,3-propanediamine with one or two moieties of glycocholic acid (GC). Both BAPA-3 and BAPA-6 inhibited Na+-dependent taurocholate (TC) uptake by Xenopus laevis oocytes expressing rat Asbt, with Ki values of 28 and 16 microM, respectively. BAPA-3 reduced Vmax without affecting Km. In contrast, BAPA-6 increased Km, with no effect on Vmax. Uptake of [14C]-GC by the last 10 cm of the rat ileum, perfused in situ over 60 min, was inhibited to a similar extent by unlabeled GC, BAPA-3 and BAPA-6. However, the intestinal absorption of these compounds was lower (BAPA-6) or much lower (BAPA-3) than that of GC. When administered orally to mice, both compounds (BAPA-3>BAPA-6) reduced the bile acid pool size, which was accompanied by up-regulation of hepatic Cyp7a1 and Hmgcr and intestinal Ostalpha/Ostbeta. A tendency towards a decreased expression of hepatic Ntcp and an enhanced expression of intestinal Asbt was also observed. Serum biochemical parameters were not affected by treatment with these compounds, except for a moderate increase in serum triglyceride concentrations. In sum, our results suggest that these compounds, in particular BAPA-3, are potentially useful tools for inhibiting the intestinal absorption of bile acids in a non-competitive manner.

Management of Dyslipidemia in Special Populations

Dyslipidemia is a significant contributor to morbidity and mortality in the industrialized world. Because it is often intertwined with other medical conditions, its management is becoming progressively more complex. Populations that pose a particular challenge to clinicians include diabetic patients, children and adolescents, elderly persons, transplant patients, patients with the human immunodeficiency virus, and patients with chronic kidney disease. When establishing lipid goals, it is imperative to have a thorough understanding of the evidence, or lack thereof, supporting the use of lipid-lowering agents among these patients. To maximize the benefits and minimize the risks of pharmacological intervention, clinicians must consider not only the unique alterations in the lipid profile of the aforementioned populations but also individual changes in patients' pharmacokinetic and pharmacodynamic parameters, as well as the potential for drug-drug and drug-disease interactions.

Management of hyperlipidemia in the pediatric population

Heterozygous familial hypercholesterolemia (FH) affects one in every 500 persons and is the most common cause of markedly elevated cholesterol levels in children. Other causes of primary hyperlipidemia include familial combined hyperlipidemia, which is also common (approximately 1%) but not usually manifest until after puberty, and very rare genetic disorders that may lead to severe hypertriglyceridemia and chylomicronemia syndrome. In children with heterozygous FH, the short-term risk of clinical events is low; therefore, management starts with stratification of risk, followed by dietary modification, and in high-risk cases, pharmacologic treatment initiated after puberty. Male gender, a family history of premature coronary heart disease, and level of low-density lipoprotein (LDL) cholesterol above 4.9 mmol/L are important determinants of risk. Trials have shown that statins effectively lower LDL cholesterol levels; in one study, statins restored endothelial function, with no clinically adverse effects. The effects of statins for longer than 2 years have not been studied. The use of bile acid sequestrants (resins) is limited by compliance and side effects. Children with homozygous FH require expert management with LDL apheresis, high doses of effective statins, and cardiologic follow-up. Ezetimibe, the first in a new class of cholesterol absorption inhibitors, may provide additional efficacy in homozygous FH.

Type 2 diabetes mellitus in adolescence: lipid and cardiovascular risk factors

This review discusses the important consequences of dyslipidemia and arteriosclerosis in type 2 diabetes as documented in studies in adults. It then examines the relatively recent upsurge in type 2 diabetes in children and adolescents, its characteristics, and its importance in directing our attention to cardiovascular risk factors in this age group. The discussion concludes with an examination of the information available about arteriosclerosis in the young and about the treatment of hypercholesterolemia in children and adolescents.

Challenges in dyslipidemia

Dyslipidemia is recognized as a significant risk factor for atherosclerotic disease. There has been a great deal of progress in the detection and management of dyslipidemia, but challenges remain, including whether to treat children, adolescents, and the elderly. Challenges include convincing physicians who tend to manage an outpatient disease with a single therapy that the management of cardiovascular risk and disease often requires multiple therapies, describing how we can combine therapies to provide an additive benefit without adding side effects or increasing morbidity, and determining whether a patient with one or more cardiovascular risk factors but a normal lipid should receive lipid-lowering therapy. Finally, there is the challenge of the Human Genome Project and predictive medicine. How will genetic information be integrated into the practice of medicine for disease prevention and management?

Brachial artery dilatation responses in healthy children and adolescents

To characterize brachial artery flow-mediated dilatation (FMD) in children, we monitored arterial diameter changes with ultrasound between 40 and 180 s after a 4.5-min forearm cuff occlusion-induced hyperemia in 105 healthy children (mean age, 11 yr; range, 9-16 yr). The peak FMD was 7.7 +/- 4.0% and occurred 79 +/- 33 s after cuff release. FMD at 60 s (5.3 +/- 4.0%) was significantly lower than the peak FMD (P < 0.0001). Twenty-three percent of the children (n = 24) reached peak FMD first after 110 s of postocclusion. Compared with others, these late responders weighed less, had smaller vessel size, and were more often girls, but had similar peak FMD. In multivariate analysis, FMD responses were inversely associated with brachial artery baseline diameter and serum cholesterol concentration. We conclude that the time to reach the peak FMD response in children varies considerably. When studying endothelial function in children with the use of the noninvasive ultrasound method, several brachial artery diameter measurements up to 120 s after cuff release are needed to determine the true FMD peak response.