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Original Articles: Gastroenterology

Pilot Study Evaluating Efficacy of 2 Regimens for Hypovitaminosis D Repletion in Pediatric Inflammatory Bowel Disease

Simek, Robert Z.*,‡; Prince, Jarod*; Syed, Sana*,‡; Sauer, Cary G.*,‡; Martineau, Bernadette; Hofmekler, Tanya*,‡; Freeman, Alvin J.*,‡; Kumar, Archana*; McElhanon, Barbara O.*,‡; Schoen, Bess T.*,‡; Tenjarla, Gayathri*,‡; McCracken, Courtney*; Ziegler, Thomas R.; Tangpricha, Vin; Kugathasan, Subra*,‡

Author Information
Journal of Pediatric Gastroenterology and Nutrition: February 2016 - Volume 62 - Issue 2 - p 252-258
doi: 10.1097/MPG.0000000000000915
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Abstract

What Is Known

  • Hypovitaminosis D is a well-known comorbidity in inflammatory bowel disease.
  • Vitamin D dosing recommendations are limited by a lack of trials especially with regard to pediatric inflammatory bowel disease.

What Is New

  • We performed a randomized pilot comparing efficacy and safety of 2 weight-based dosing regimens using weekly oral vitamin D3 for 6 weeks.
  • We build on the broad vitamin D dosing recommendations from the Institute of Medicine and American Academy of Pediatrics.
  • We demonstrated significant repletion of hypovitaminosis D safely using higher dosing of oral vitamin D3.

The inflammatory bowel diseases (IBDs) Crohn disease (CD) and ulcerative colitis are chronic, relapsing, inflammatory diseases of the digestive tract that have a significant impact on growth and development in children and on overall health, nutritional deficiencies, and quality of life across all age groups (1). The natural history of these diseases can range from mild symptoms that may be relatively well controlled with medical management to severe, recalcitrant disease with numerous complications requiring multiple intestinal resection surgeries to excise inflamed bowel.

Vitamin D has been comprehensively studied for its effects in calcium, phosphorus, and bone metabolism; however, several lines of evidence suggest that vitamin D plays an important role in immune regulation, innate immune responses, adaptive immunity, and immune tolerance (2). Vitamin D deficiency is common in patients with IBD, as indicated by numerous retrospective and cross sectional studies (3–5). In addition, severe compromised bone health in IBD can occur and result in osteoporosis and increased fracture risk (6). There is growing epidemiological evidence to suggest that vitamin D plays a role in the development of IBD and influences disease severity (3). Although the animal and in vitro models show the vital role of vitamin D in moderating disease activity and immune tolerance in IBD, the evidence from human IBD studies are still developing (2).

Serum 25-hydroxyvitamin D (25[OH]D) is the marker of vitamin D status in humans, but there has been speculation of what defines an adequate level of 25(OH)D in humans. The Institute of Medicine has defined ≥20 ng/mL (50 nmol/L) to be a sufficient serum 25(OH)D concentration and this stance has been endorsed by the American Academy of Pediatrics (7). In addition, the Institute of Medicine specifically argues that levels >30 ng/mL (75 nmol/L) do not provide additional benefit (8). The Endocrine Society suggests a higher cutoff of 30 ng/mL (75 nmol/L) to be the sufficient concentration of 25(OH)D because this is the level that is needed to be reached to reduce parathyroid hormone activity (9). Although defining adequate 25(OH)D level is still controversial, there is a growing support to use 30 ng/mL (75 nmol/L) as the adequate cutoff. Because bone disease is more common in the IBD population (6), this measurement is even more important for this population. Many recent gastrointestinal publications have used the higher cutoff of 30 ng/mL (75 nmol/L) as the optimal 25(OH)D level desired (3,10,11).

Known risk factors for vitamin D insufficiency or deficiency in IBD include seasonality, severe disease activity, extensive small bowel involvement or resection, dark skin pigmentation, and corticosteroid treatment (12). Joint guidelines from the North American and European Societies for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN and ESPGHAN, respectively) (5), published in 2011, recommend that pediatric gastroenterologists treating pediatric patients with IBD consider monitoring vitamin D status yearly, and that they treat hypovitaminosis D to establish and maintain optimal vitamin D levels. These recommendations suggest the use of a weekly vitamin D treatment regimen because the issues of compliance in pediatric and adolescent patients with chronic diseases are of significant concern. Furthermore, several studies have suggested that vitamin D3 (cholecalciferol) has 2- to 3-fold greater bioavailability over vitamin D2 (ergocalciferol), which is commonly prescribed to be a high-dose weekly treatment regimen for vitamin D deficiency in the United States (13–16).

Focused studies of vitamin D dosing in children with IBD had been virtually absent from the literature until 2011. Recent pioneering studies by Pappa et al (17,18) have begun to explore potential dosing regimens for the treatment of hypovitaminosis D in these children with IBD. The results from those studies suggest that higher weight-adjusted dosing may be more appropriate and safer in children. There is a need for higher and effective dosing regimen studies for the repletion of vitamin D for hypovitaminosis in children with IBD.

The primary aim of the present study was to compare the efficacy of 2-week oral dosing regimens of vitamin D3 for the repletion of hypovitaminosis D in children and adolescents with known IBD. Secondary aims included (1) evaluation of the safety of the high-dose weekly dosing of vitamin D3 in pediatric patients with IBD and (2) evaluation of any differences in serum 25(OH)D levels among subjects as a function of skin pigmentation. Weekly regimens were chosen to improve compliance, which is a common concern with children and adolescents with IBD.

METHODS

Participants

Potential subjects were identified from the Pediatric IBD Clinics at Emory Children's Center and Children's Healthcare of Atlanta who had recently (within 3 months of enrollment) been screened for serum 25(OH)D concentrations as a part of their routine care. Inclusion criteria mandated screening serum 25(OH)D level <30 ng/mL (75 nmol/L), ages between 8 and 21 years, weight >20 kg, and confirmed diagnosis of IBD (either CD or ulcerative colitis) by a pediatric gastroenterologist. Any patients with the inability to swallow the study drug capsules were also excluded. Because vitamin D metabolism can also be affected by underlying chronic kidney or liver diseases, those with a known history of renal or hepatobiliary disease were excluded. We also did not include those who had a history of recent use of systemic corticosteroids (within 60 days of enrollment). Fitzpatrick skin pigmentation score and type (19), which are commonly used objective measures of skin pigmentation, were recorded for comparison in all of the subjects at enrollment. Subjects were randomized by permutated block design to 1 of the 2 study arms by the Children's Healthcare of Atlanta Research Pharmacy. Both subjects and investigators were blinded to the group assignment. The research pharmacist also purchased the vitamin D3, packaged it, and dispensed it. The full trial protocol can be accessed at ClinicalTrials.gov, ID number NCT02076750, and can be accessed on request from the authors.

Vitamin D Dosing

Vitamin D3 was purchased from a commercial source (Nature's Bounty, Bohemia, NY). Subjects were provided either 5000 IU vitamin D3 per 10 kg body weight once weekly for a total of 6 weeks (maximum weekly dose of 25,000 IU, maximum cumulative dose of 150,000 IU) or 10,000 IU vitamin D3 per 10 kg body weight once weekly for a total of 6 weeks (maximum weekly dose of 50,000 IU and maximum cumulative dose of 300,000 IU). Subjects and caregivers were contacted weekly by telephone throughout the intervention period of 6 weeks to ensure and document compliance with the study intervention. Pill count was done at follow-up visits.

Sample Collection and Laboratory Assays

Whole blood was collected from all the subjects at the time of enrollment (baseline) and at 8 and 12 weeks (∼2 and 6 weeks, respectively, following the last dose of the study drug). Serum was isolated and stored at −80°C. Samples were analyzed in-batch for baseline and follow-up concentrations of serum 25(OH)D, total serum calcium (Ca), and parathyroid hormone (PTH). Serum 25(OH)D concentration was analyzed in a single batch by liquid chromatography-tandem mass spectrometry (LC/MS/MS). Ca concentrations in serum were determined using colorimetric assays purchased from Point Scientific (Canton, MI). Serum PTH was determined using the Food and Drug Administration–approved DiaSorin intact PTH immunoradiometric assay. All the 3 biochemical metrics were analyzed in-batch by Heartland Assays (Ames, IA).

Sample Size

This trial was designed to compare the efficacy of 2 treatment arms to replete hypovitaminosis D. Given 20 patients per group (N = 40 total), we had >90% power to detect a 10-ng/mL mean increase in serum 25(OH)D levels from baseline to week 8 in each dosing group. Power was calculated assuming a standard deviation of differences of 10 ng/mL (25 nmol/L) using a paired t test with a 0.05 level of significance. In addition, using similar assumptions, 20 patients per group achieves 80% power to detect an average difference of 9.1 ng/mL (22.7 nmol/L) between dosing groups at 8 weeks using a 2-sample t test.

Safety and Clinical Adverse Events

Safety was based on the evaluation of serum calcium and PTH levels at baseline, week 8, and week 12. Patients were also screened at each study visit and at each weekly phone call for clinical signs or symptoms of hypercalcemia with either intervention during the study period. Specifically, patients were asked regarding gastrointestinal symptoms (cramps, pain, diarrhea, vomit, and nausea) and musculoskeletal symptoms (pain, cramps, and twitches). Clinical adverse events were reported at each visit using specifically designed case report forms. All the participants reporting adverse events were retained for analysis regardless of withdrawn status.

Statistical Methods

Statistical analyses were performed using SAS version 9.3 (SAS Institute, Cary, NC). Statistical significance was assessed at the 0.05 level unless otherwise noted. Analysis was performed using intention-to-treat design, and randomization assignments were maintained. Two-sample t tests, Mann-Whitney U tests, and χ2 tests were used to compare demographic and clinical characteristics between randomization groups. Repeated measures analysis of variance models were used to examine serum 25(OH)D concentrations within and between dosing groups over time while controlling for the correlation among observations made on the same study participant. For these models, an autoregressive correlation structure was used. Within each dosing group, serum 25(OH)D concentrations were compared at different time points (ie, week 0, week 8, and week 12) using a Tukey-Kramer multiple comparison procedure. Interactions between dosing group and time were initially included in all models and retained if P < 0.10. Similar analyses were used to compare Ca and PTH concentrations over time and between groups.

Ethical Considerations and Institutional Oversight

This interventional clinical study was conducted in accordance with the principles of the Declaration of Helsinki and with appropriate approval and oversight by the institutional review boards of Emory University and Children's Healthcare of Atlanta.

RESULTS

Treatment Assignment

The subject enrollment flow diagram of the pilot study is given as Figure 1. We enrolled a total of 40 patients in our study between April 8 and November 25, 2013, but 6 patients did not follow-up or were unintentionally exposed to corticosteroids. Of the remaining 34 patients, 16 subjects were randomized to the 5000 IU/10 kg group, and 18 subjects were randomized to the 10,000 IU/10 kg group. Two additional subjects withdrew from the study after enrollment; one of these subjects withdrew after single episode of vomiting that occurred in the week after starting the intervention, and the other subject withdrew because of prolonged diarrhea, which was preexisting at enrollment. Twenty-two subjects completed all the 3 study visits, 5 subjects completed only 2 study visits, and 5 subjects completed only the enrollment visit and did not return for follow-up thereafter. Randomization was balanced across both study groups (Table 1). Adherence to therapy (as assessed by pill count done at follow-up visits) was 100% in both arms of the study.

FIGURE 1
FIGURE 1:
Subject recruitment flow diagram showing selection and final disposition of study participants.
TABLE 1
TABLE 1:
Comparison of demographic and clinical variables between groups

Demographics

Our study cohort had a mean age of 16 years (SD ± 2.8), range 11 to 20 years. Study participants were predominantly boys (63%) and African American (66%). The vast majority of patients had CD (88%) and were classified into groups having darker skin types groups using the Fitzpatrick scales. There were no significant differences in demographic characteristics between the randomization groups of vitamin D 5000 IU/10 kg and 10,000 IU/10 kg (Table 1).

Vitamin D Concentrations

Serum 25(OH)D concentrations were evenly matched between the 5000/10 kg and 10,000 IU/10 kg groups at baseline (week 0; 24.0 ± 7.0 and 23.7 ± 8.5 ng/mL, respectively; P = 0.920). A significant increase in serum 25(OH)D concentrations occurred in both treatment groups at week 8, with the higher dosing group increasing the serum 25(OH)D concentration more (increase of mean 25(OH)D from 23.7 ± 8.5 ng/mL at baseline to 49.2 ± 13.6 ng/mL at 8 weeks; P < 0.001) than the lower dosing group (increase of mean 25(OH)D from 24.0 ± 7.0 mg/mL at baseline to 41.5 ± 9.6 ng/mL at 8 weeks; P < 0.001) (Table 2 and Fig. 2). Although not statistically different, the mean 25(OH)D concentration for the 10,000 IU/10 kg dosing regimen was higher than for the 5000 IU/10 kg regimen at both 8- and 12-week follow-up visits (49.2 ± 13.6 and 41.5 ± 9.6 at week 8; P = 0.105, vs 35.1 ± 8.4 and 30.8 ± 4.2 at week 12; P = 0.122, respectively). We also looked at patients <50 kg. We had a total of 11 subjects (34%) <50 kg, 7 of them were between 45 and 49 kg, and 4 were <45 kg. The serum 25(OH)D concentration of the patients <50 kg at baseline, week 8, and week 12 had a similar trend to the entire group of patients (the 10,000 IU/kg group had a mean 24(OH)D serum of 27.0 ± 4.3 ng/mL at baseline, 50.8 ± 11.5 ng/mL at week 8, and 36.1 ± 6.4 ng/mL at week 12; the 5000 IU/kg group had a mean 24(OH)D serum of 21.3 ± 8.0 ng/mL at baseline, 41.0 ± 12.0 ng/mL at week 8, and 30.7 ± 6.2 ng/mL at week 12).

TABLE 2
TABLE 2:
Comparison of serum 25(OH)D concentrations at weeks 0, 8, and 12
FIGURE 2
FIGURE 2:
Mean 25-OH vitamin D3 concentrations enrollment, at treatment start (week 0), 8 weeks, and 12 weeks following the start of treatment. Standard error bars are shown. The gray box indicates the timing of the intervention (oral cholecalciferol once weekly for a total of 6 doses).

Calcium and PTH

For the 10,000 IU/10 kg regimen, there was no significant change in mean serum Ca concentration throughout the study period. There was a small increase in serum Ca for the 5000 IU/10 kg group between baseline and week 8 (11.3 ± 0.7 to 11.9 ± 0.7); however, after adjusting for multiple comparisons, this difference was not statistically significant. Similarly, for the 5000-IU regimen, there was no significant change in the mean serum PTH concentrations throughout the study period. For the 10,000-IU regimen, there was a decrease in PTH from baseline to week 8 (45.8 ± 23.7 to 33.6 ± 14.8); however, after adjusting for multiple comparisons, this difference was not statistically significant. Furthermore, serum Ca and PTH concentrations were similar between groups at each study period (Table 3). Mean serum Ca concentrations (mg/dL) for the 5000 IU/10 kg group and 10,000 IU/10 kg group were 11.3 ± 0.7 versus 11.4 ± 0.5 (P = 0.644) at week 0, 11.9 ± 0.7 versus 11.7 ± 0.7 (P = 0.573) at week 8, and 11.4 ± 0.8 versus 11.7 ± 0.7 (P = 0.573) at week 12, respectively. Mean serum PTH concentrations (pg/mL) for the 5000 IU/10 kg group and 10,000 IU/10 kg group were 37.2 ± 20.1 versus 45.8 ± 23.7 (P = 0.289) at week 0, 30.2 ± 13.3 versus 33.6 ± 14.8 (P = 0.647) at week 8, and 27.3 ± 9.5 versus 38.9 ± 17.4 (P = 0.061) at week 12, respectively.

TABLE 3
TABLE 3:
Calcium and PTH levels over time

Safety

No subject exhibited clinical signs or symptoms of hypercalcemia with either intervention during the study period, and no serious adverse events were observed. Furthermore, all serum Ca and PTH values did not significantly increase from baseline through the intervention period.

DISCUSSION

This pilot trial provides new information to inform optimization of vitamin D3 (cholecalciferol) repletion dosing for hypovitaminosis D in pediatric patients with IBD. The present guidelines for the treatment of vitamin D insufficiency in healthy children have included wide dosing ranges (84,000–600,000 IU, cumulatively), without specific guidance on weight- or age-based dosing of vitamin D (20). It has been suggested that higher doses are necessary in children and adolescents with IBD for a variety of reasons (4), and cumulative doses of 220,000-IU vitamin D3, independent of age or weight, have been estimated to provide sufficient repletion of hypovitaminosis D in pediatric patients with IBD (18). Our results show significant elevations in serum 25(OH)D concentrations >30 ng/mL (75 nmol/L) with both 5000 IU vitamin D3/10 kg once weekly for a total of 6 weeks (maximum weekly dose of 25,000 IU and maximum cumulative dose of 150,000 IU) or 10,000 IU vitamin D3/10 kg once weekly for a total of 6 weeks (maximum weekly dose of 50,000 IU and maximum cumulative dose of 300,000 IU). This was notable both at 8- and 12-week follow-up visits indicating that both dosing regimens are effective in replenishing vitamin D in hypovitaminosis D in pediatric IBD. A novel component of our trial was that we used much higher treatment doses of vitamin D3 as compared with other pediatric trials (17,18), which used a maximum daily dose of vitamin D3 2000 IU with higher weekly dosing of vitamin D2 not D3(18). Another key finding from our study is our demonstration that serum 25 (OH)D concentrations in both patient groups began to decrease once the treatment was stopped, suggesting the need for a longer duration of repletion and/or maintenance therapy.

An important area of investigation has been differences in vitamin D status with regard to ethnicity/race. Our group has previously demonstrated that African Americans tend to have low vitamin D status or vitamin D deficiency regardless of their IBD disease status (21). Overall bone health appears to be affected by IBD and vitamin D status in whites, whereas the bone health of African-Americans may not be affected by the presence of IBD or by the overall vitamin D status of African Americans. In our present study, we used an objective method of classifying skin color pioneered by Fitzpatrick (19). Stratifying by skin pigmentation, we did not see differences in baseline or posttreatment vitamin D status, but these data are limited by our small sample size.

It is also important to note that our study used vitamin D3 (cholecalciferol), which has greater bioavailability than vitamin D2 (ergocalciferol), and we have demonstrated that a higher dosing regimen of vitamin D3 has a well-tolerated safety profile in terms of serum calcium and PTH levels. Furthermore, given that we did not additionally provide our patients supplemental calcium, our results suggest that improved vitamin D status improves calcium economy in patients with IBD, removing the need for prescribing additional calcium as has been done in previous trials by Pappa et al (4,5,12,17,18). Although serum PTH concentration has been shown in both adults and children to have a small, inverse correlation with serum 25(OH)D concentration (22,23), in our study there was no statistically significant change in mean serum Ca or PTH concentrations for either treatment group, and no differences were observed between treatment groups.

Our study was limited by our small sample size. The study was powered to detect differences between vitamin D dosing regimens at 8 weeks given 20 patients per group. Our effective sample size for analysis was only 32 (14 and 18 for 5000 and 10,000, respectively) because of patients leaving the study prematurely and unintentional corticosteroid exposure. In addition, not all of the enrolled patients had serum collected at every time point. Thus, we were inadequately powered to detect smaller differences in our outcome measures between dosing groups; however, we were able to demonstrate that these high vitamin D dosing regimens were safely able to increase serum 25(OH)D levels and effectively replete hypovitaminosis D in our study cohort. In addition, although not statistically significant, the 10,000 IU/10 kg regimen resulted in mean serum 25(OH)D levels that were 19% higher than the 5000 IU/10 kg regimen group at 8 weeks. The lack of a control group did not allow us to compare our findings against healthy children and adolescents. Another limitation was the lack of diet history and the lack of sun exposure history, which certainly affects a patient's serum 25(OH)D level. We did not collect these data because they are frequently prone to recall bias.

Finally, our cohort consisted of older adolescents (mean age 16 ± 2.8 years) who are predominantly boys (59%). Thus, our results may not be generalizable to a younger female demographic. Also, the mean 25(OH)D level at the start of the study was 24.0 ng/mL (60 nmol/L). As we had mentioned earlier, there is a large variation in the literature of what constitutes a deficiency (20,24). For our study, we chose to define serum 25(OH)D levels ≤20 ng/mL (50 nmol/L) to be deficient, and serum levels >20 but ≤30 ng/mL (>50 but ≤75 nmol/L) to be suboptimal as has been suggested by several studies (25–28). Because of the initial serum 25(OH)D levels being in the suboptimal category, our results may not be generalizable to lower serum levels.

Despite the small sample size, this is the first randomized pediatric trial that demonstrated effective repletion of hypovitaminosis D using high-dose vitamin D3 supplementation in patients with IBD. The present study provides initial evidence to be further corroborated with larger scale trials—that vitamin D3 doses as high as 10,000 IU/10 kg weekly are safe and well tolerated.

In conclusion, we have found that either 5000 or 10,000 IU/10 kg weekly dosing with oral vitamin D3 for 6 weeks is both safe and effective at normalizing vitamin D nutriture in pediatric patients with IBD. Based on 25(OH)D concentrations measured at 12 weeks, our data also suggest, that the effect of weekly dosing is diminished 12 weeks out. This suggests that perhaps after an initial induction regimen, repletion needs to continue for a longer maintenance duration to potentially have a more sustained effect on vitamin D nutriture. Therefore, we recommend both repletion and maintenance vitamin D therapy is necessary to replete and maintain optimal vitamin D status, and further clinical studies are merited to establish optimal chronic vitamin D3 dosing regimens in pediatric IBD.

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Keywords:

children; Crohn disease; ulcerative colitis; vitamin D

© 2016 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology,