Development and Testing in Healthy Adults of Oral Hydrocortisone Granules With Taste Masking for the Treatment of Neonates and Infants With Adrenal Insufficiency

Background:

Treatment of neonates and infants with adrenal insufficiency is unsatisfactory because unlicensed hydrocortisone formulations are used.

Objectives:

The objectives were to survey current hydrocortisone prescribing practice and develop a novel hydrocortisone formulation, Infacort.

Methods:

The use of hydrocortisone by European pediatric endocrinologists was surveyed. Based on this, an oral hydrocortisone granule formulation, Infacort, with taste masking was developed and evaluated in vitro and then in vivo in a phase I pharmacokinetic study.

Results:

The survey showed that pediatricians use a variety of unlicensed compounded adult medications at doses of between 0.5 and 5 mg. Infacort was formulated with a taste-masking layer stable for at least 5 minutes in aqueous media and was produced in unit doses of 0.5, 1, 2, and 5 mg. Infacort 10 mg is the bioequivalent of a 10-mg hydrocortisone tablet (mean area under the curve from zero to infinity [AUC_0-inf] ratio, 101%; 90% confidence interval, 96–107%). Mean cortisol maximum concentration (C_max) and AUC_0-inf values after administration of Infacort were linear with dose and dose proportional when adjusted for saturable plasma protein binding. Subjects rated Infacort as “not good or bad” for smell (86%), feel in the mouth (71%), and taste (79%). No serious adverse events were reported.

Conclusions:

This phase 1 study demonstrates that Infacort is safe, well tolerated, of neutral taste, bioequivalent to hydrocortisone licensed for adults, and shows dose proportionality with respect to cortisol exposure. Infacort is expected to facilitate optimization of hydrocortisone dosing in neonates and children with adrenal insufficiency; however, clinical studies will be required to demonstrate efficacy in this patient age group.

Adrenal insufficiency or cortisol deficiency may be classified as primary (dysfunction of the adrenal gland) or secondary (dysfunction of the pituitary gland). The condition can be further classified as congenital or acquired. In neonates and infants, congenital primary adrenal insufficiency is the most common etiology as a result of either adrenal hypoplasia or hyperplasia (1). Congenital adrenal hyperplasia (CAH) is the most common congenital genetic endocrine disorder, and it results from mutations in the cortisol synthesis pathway in the adrenal glands. Mutations in the gene for 21-hydroxylase, a key enzyme in cortisol and aldosterone synthesis, account for 95% of cases. 21-Hydroxylase deficiency has an incidence of 1:10 000 to 1:15 000 live births for severe mutations causing classic CAH, which manifests in the neonatal period (1). Treatment for all causes of adrenal insufficiency is cortisol replacement, with hydrocortisone given to children according to body surface area two to four times daily (2).

Adrenal insufficiency was fatal until the discovery of cortisone in the 1930s and hydrocortisone in 1951 (3). In 1963, Dunlop (4) published a report of 86 adrenal insufficiency patients he had cared for between 1928 and 1958, showing that whereas all patients died before cortisone became available, only one of his patients had died after starting treatment with cortisone. There is now an increasing cohort of adult patients who were born with congenital adrenal insufficiency, most of whom have CAH. It is apparent that these patients have poor health outcomes, such as increased obesity, a poor metabolic profile, and impaired quality of life (5, 6). Most evidence suggests that the poor health outcomes relate to inadequate treatment, specifically with glucocorticoid replacement therapy (7), and the onset of obesity and hypertension is seen even in childhood (6). Using final adult height as a surrogate marker of treatment efficacy in childhood, it is evident that treatment has improved over time but that young adults are still shorter than their predicted adult height, suggesting that treatment could be further optimized in children (8). The challenge for pediatricians in treating adrenal insufficiency is to maintain a balance between too little hydrocortisone, with the risk of adrenal crisis, and too much, with the risk of glucocorticoid excess resulting in growth suppression, hypertension, and obesity.

Current treatment for adrenal insufficiency in neonates and infants is unsatisfactory because adult dosage formulations unlicensed for children are used. These preparations are usually difficult to administer, often not available in the appropriate unit dose, and frequently bitter to taste, and they may give rise to inconsistencies in dose because the content uniformity of the dosage form cannot be verified. Because there is no licensed hydrocortisone formulation for children under 6 years of age, hydrocortisone is often compounded by pharmacists using adult hydrocortisone tablets. In a recent study of compounded hydrocortisone, up to 20% of the batches did not meet the European Pharmacopeia accuracy and precision criteria (9), indicating that current therapy is inadequate in a significant proportion of children treated with compounded hydrocortisone. Thus, there is a need for specifically designed and licensed hydrocortisone formulations for this vulnerable pediatric patient group.

Based on a survey of current practice in the treatment of neonates and infants, we developed a new formulation of hydrocortisone, Infacort, using multiparticulate (granule) technology. We report the palatability, bioequivalence with respect to a conventional hydrocortisone tablet formulation, and dose proportionality with respect to cortisol exposure after administration of Infacort to healthy adults.

Subjects and Methods

Survey of pediatric endocrinologists

To determine how hydrocortisone is prescribed for infants and neonates with adrenal insufficiency, an international web-based survey was conducted over a period of 6 months. Through the monthly newsletter of the European Society of Pediatric Endocrinology, healthcare providers across Europe were asked to specify their current practice in the treatment of neonates and infants with adrenal insufficiency by answering a short online questionnaire. The survey comprised 11 questions with options for comments.

Infacort formulation

The Infacort formulation of hydrocortisone with taste masking is based on granule, multilayered, multiparticulate technology (Figure 1) (10). Hydrocortisone is applied to inert microcrystalline core granules that are then coated with a binding layer and a taste-masking layer and placed in hypromellose capsules (Vcaps; Capsugel). The total dose of hydrocortisone can be modified by altering the fill-weight of the granules in a single capsule. Infacort was administered by placing the granules from a capsule on a teaspoon (∼ 6 mL), tipping them onto the back of the subject's tongue, swallowing the granules with 100 mL of water, followed by a further 100 mL of water to rinse the mouth.

In vitro dissolution

The dissolution of hydrocortisone from Infacort granules (n = 6) was assessed using the USP paddle apparatus (Apparatus II). Dissolution vessels were filled with 700 mL of United States Pharmacopoeia-simulated gastric fluid (pH 1.2) and prewarmed to 37 ± 0.5°C. Once the medium was at the required temperature, the Infacort granules were added to each vessel, with the stirring rate set at 75 rpm. At 15, 30, 45, 60, and 120 minutes, 1.5-mL samples were taken for analysis. Hydrocortisone concentrations were determined by reversed-phase HPLC with UV detection at 254 nm using an Agilent 1100/1200 System (Agilent). To evaluate the effect of the taste-masking layer of the formulation under conditions expected in the mouth, the same procedure was followed, except that phosphate buffer (pH 7.0) was used as the dissolution medium, the stirring rate was set at 50 rpm, and samples were taken at 1, 2, 3, 4, 5, 6, and 7 minutes.

Bioequivalence and dose proportionality

An open-label, randomized crossover study was carried out at Simbec Research Ltd in 16 dexamethasone-suppressed healthy male volunteers aged 18 to 60 years. Each subject received 0.5-, 2-, 5-, and 10-mg doses of Infacort and a 10-mg dose of a conventional hydrocortisone tablet (Auden Mackenzie Ltd). For each dosage administration, the subjects were admitted to the clinical unit on the afternoon of day 1 and remained in the unit until completion of all assessments on day 2. Each subject received 1-mg dexamethasone (to suppress endogenous cortisol production) at approximately 10 pm on day 1 and at approximately 6 am and noon on day 2. Infacort or the reference hydrocortisone tablet was administered on the morning of day 2 at approximately 7 am. A member of the study team administered the granules to the back of the subject's tongue. There was a washout period of at least 7 days between each dosing period.

Ethics

The studies were approved by the South East Wales Research Ethics Committee, and all participants gave written informed consent. The study protocol was authorized by the Medicines and Healthcare products Regulatory Agency.

Serum cortisol was measured by liquid chromatography-tandem mass spectrometry using an Applied Biosystems MDS Sciex API365 mass spectrometer and a PerkinElmer series 200 LC system with an electrospray source in negative ionization mode. The lower and upper limits of quantitation were 1.38 and 690 nmol/L, respectively. Reproducibility (relative SD) was < 15% at the lower limit of quantitation quality control (1.38 nmol/L) and < 10% at the low, medium, and high quality control levels (22, 83, 552 nmol/L). One ng/mL of cortisol is equivalent to 2.759 nmol/L.

Mean unbound serum cortisol concentrations were predicted from measured total concentrations based on data for the saturable binding of cortisol to plasma proteins reported by Lentjes and Romijn (11).

Determination of sample size

From a previous study (12), the within-subject coefficient of variation for area under the curve from zero sample to final sample (AUC_0-t) cortisol was approximately 20%. A sample size of 16 subjects was considered sufficient to detect a 20% difference between test and reference formulations with a power of 80% and alpha of 5%, based upon a test vs reference ratio of 1.00.

Statistical analysis

Pharmacokinetic (PK) end-points

The PK end-points were derived from the individual serum cortisol concentration-time data using WinNonlin Phoenix 32. For the calculation of PK end-points, serum cortisol concentrations below the limit of quantification were assigned a value of zero. In case of a deviation from the theoretical time, the actual time of blood sample was used in the calculation.

Bioequivalence

After logarithmic transformation, C_max, AUC_0-t, and AUC_0-inf values were subjected to a mixed effects ANOVA including fixed effects for sequence, period, and treatment and a random effect for subject nested within sequence. Point estimates and 90% confidence intervals (CIs) were constructed for the contrasts between treatments using the residual mean square error obtained from the ANOVA. The point and interval estimates were back-transformed to give estimates of the ratios of the geometric least squares means and corresponding 90% CI.

Dose proportionality

Dose proportionality was assessed by performing a regression analysis of the log-transformed C_max, AUC_0-t, and AUC_0-inf values vs the log-transformed dose using a power model with a fixed effect for dose and a random effect for subject. For each parameter, a point estimate and 95% CI has been calculated for the slope of the regression line. Dose independence was assessed for t_1/2 and oral clearance (CL/F) by performing a regression analysis of the untransformed parameters vs dose with a fixed effect for dose and a random effect for subject. For each parameter, a point estimate and corresponding 95% CI have been calculated for the slope of the regression line.

Assessment of palatability

The palatability of Infacort was assessed at the time of dosing during each of the four Infacort treatment periods by questionnaire. Subjects were asked whether taste, smell, and feeling in the mouth were “very good,” “somewhat good,” “good,” “not good or bad,” “somewhat bad,” or “very bad.” They were also asked to best describe how the medication tasted, smelled, and felt in the mouth by selecting from a list of variables with the provision to capture any additional descriptive words.

Results

Survey of pediatric endocrinologists

Over a period of 6 months, 67 participants from 16 countries participated in the online survey, with most replies coming from Germany (48%). Of the 92% of participants confirmed to be health care professionals, 46% stated that they were working in a university hospital setting, and 25% were in a specialized pediatric endocrine practice. The hydrocortisone formulations prescribed for children under the age of 6 years are shown in Figure 2A; the most frequent answer (60%) to the questionnaire with respect to administration was “licensed tablets to be divided,” followed by prescription of individualized capsules (55%). The use of a liquid suspension was the most favored answer with respect to the use of “other” forms of administration. The prescribed dosage of hydrocortisone for children with adrenal insufficiency varied from 0.5 to 5 mg given one to four times daily (thrice daily, 94%; and one, two, and four times daily, just 2% each), with 1 and 2 mg being the most common doses (82 and 68%, respectively; Figure 2, B and C). Steroid drugs other than hydrocortisone were prescribed by 24% of the participants in the questionnaire, most commonly fludrocortisone (56%). Most responders recommended administration of hydrocortisone at fixed intervals (64%) or with meals (19%). Schemes of administrating hydrocortisone once or twice daily were also reported using tablets licensed for adult use.

In vitro dissolution

The dissolution of hydrocortisone from Infacort granules in simulated gastric fluid indicated a release profile (greater than 75% release within 45 min) in accordance with the European Pharmacopeia definition of an immediate drug release product (13). Evaluation of drug release in neutral phosphate buffer indicated < 10% dissolution after 5 minutes compared to over 60% dissolution with crushed adult tablets (data not shown), confirming that the taste-masking layer was expected to provide an effective barrier to significant drug dissolution in the mouth.

Serum cortisol concentrations

Sixteen subjects, aged 41 (14) years [mean (SD)], received all five scheduled doses: four Infacort doses and one 10-mg immediate-release hydrocortisone tablet. Two subjects had inadequate endogenous cortisol suppression (basal cortisol > 50 nmol/L) before administration of 10-mg Infacort, and a different subject had inadequate endogenous cortisol suppression before administration of 0.5- and 5-mg Infacort. The analysis of serum cortisol–time profiles did not adjust for baseline levels because these were suppressed, but it excluded those from subjects where the predose cortisol level indicated inadequate cortisol suppression.

Mean serum cortisol concentrations were similar after administration of Infacort and the reference hydrocortisone formulation at the 10-mg dose level (Figure 3). The geometric least squares mean, test/reference ratios of C_max and AUC_0-inf indicated that 10-mg Infacort is bioequivalent (CI between 80 and 125%) to the reference 10-mg hydrocortisone formulation (Table 1). Median time of maximum concentration (t_max) values were 0.75 and 1.0 hours for Infacort and reference hydrocortisone, respectively (P = .48), and cortisol t_1/2 values were also similar after administration of the two formulations (3.27 and 3.18 h, respectively).

Mean AUC_0-inf values after administration of Infacort increased linearly but less than proportionately with dose (0.5–10 mg) (Figure 4A), as did mean C_max values (data not shown). The slope of the C_max vs dose relationship was 0.637 (95% CI, 0.600–0.675), and that for the AUC_0-inf vs dose relationship was 0.428 (95% CI, 0.392–0.464). The mean t_1/2 appeared to decrease with dose over the dose range 0.5–10 mg, as reflected by a slope of −0.528 (95% CI, −0.760 to −0.296). When mean AUC_0-inf values were corrected for concentration, dependent plasma binding dose proportionality was evident (Figure 4B).

Administration and palatability

There was no occasion where administration failed because of significant spillage of granules. The capsules and teaspoon were inspected for residual granules; on one occasion, granules were retained on the teaspoon after initial administration but then were taken by the subject. On another single occasion, some granules were left in the capsule after initial administration, but it was possible to evacuate them entirely onto the dosing spoon for subsequent administration. In five capsules, approximately two, four, five, 12, and 50 granules, respectively, were retained and could not be evacuated. The weight of the capsule with approximately 50 retained granules was 138 mg, and the weight of the remaining granules was approximately 14 mg. This compares with a fill weight of the 5-mg capsule of 757 mg (0.66% hydrocortisone). Therefore, taking account of the tolerance window allowed when filling the capsules, the amount of remaining granules, and therefore hydrocortisone not dosed, was negligible.

The overall response rate for palatability was 98%. Infacort was described as “not good or bad” for smell on 86% of occasions, for feel in the mouth on 71% of occasions, and for taste on 79% of occasions. In addition, 93% of reports indicated “no smell,” and 76% indicated “neutral” or “no taste.” One subject described the medication as tasting “very bad” after 5- and 10-mg Infacort administration. The same subject also described the medication as feeling “somewhat bad” in his mouth after 2-mg Infacort, together with dysgeusia. Palatability was not assessed for hydrocortisone.

Safety

There were no serious adverse events and no clinically significant differences in treatment-emergent adverse events for biochemistry, hematology, urinalysis, vital signs, or electrocardiogram data between Infacort and conventional hydrocortisone, nor any dose-related effects.

Discussion

The survey of European pediatric endocrinologists indicated a wide variety of hydrocortisone treatment regimens administered to neonates, infants, and children under 6 years of age with adrenal insufficiency. Dosage varied between 0.5 and 5 mg, the most common being 1 and 2 mg. In some cases, adult tablets are being used with a lower dosage frequency (once or twice daily). The practice of dividing adult tablets into halves or quarters and the dispensing of capsules containing crushed tablets is common. With regard to the later procedure, a recent study indicated that up to 20% of batches did not meet the European Pharmacopeia accuracy and precision criteria (9). Thus, the survey confirmed the need for a licensed infant preparation of hydrocortisone allowing dosing from 0.5 mg and including unit doses of 1 and 2 mg. Indirect evidence that treatment of adrenal insufficiency in neonates and infants is not optimized comes from studies of health outcomes in patients with CAH. These patients are relatively short in stature and have an increased incidence of obesity and hypertension, which could relate to early childhood treatment (6–8). Pediatricians may tend toward giving excess glucocorticoid to avoid an adrenal crisis in the early years of life. Thus, there is an unmet need for a hydrocortisone formulation that is designed for the pediatric population and allows optimization of glucocorticoid therapy.

In developing Infacort, we chose to produce unit doses of 0.5, 1.0, 2.0, and 5.0 mg. Formulation factors included granule size, their content of hydrocortisone, and the thickness of the taste-masking layer. The number of granules was dictated by the need to ensure that variability in dosage at the lowest dose would not be significant if a few granules were not swallowed and by the requirement to accommodate them into the capsule at the highest dose. In accordance with Food and Drug Administration guidelines, granules up to 2.5 mm in diameter, with no more than 10% variation over this size to a maximum of 2.8 mm, are acceptable for administration to young children and do not cause problems with choking (14). Therefore, in Infacort we used granules of 500 μm giving approximately 270 granules in the 0.5-mg capsule. We chose to administer the medication dry because creating a uniform suspension is difficult and may result in residue on the teaspoon or syringe. In addition, the use of dry granules allows for longer stability and intact retention of the taste-masking layer. This study confirmed that Infacort is easy to administer; there was no failed dosing, only a few granules on a few occasions remained in the capsule, and systemic exposure was confirmed in all subjects.

Taste masking is important with respect to the administration of hydrocortisone to infants because patients often complain that it has a bitter taste. The taste-masking layer incorporated in the Infacort formulation was designed to remain intact for approximately 5 minutes in aqueous solution. In vitro dissolution testing confirmed that there was a delay in hydrocortisone release of 5 minutes and that > 75% of the drug was released over 45 minutes, commensurate with an immediate-release drug formulation. Measurement of serum cortisol concentrations indicated that the taste masking had no impact on systemic exposure because Infacort was shown to be bioequivalent to a conventional hydrocortisone tablet formulation. There is no standard, validated questionnaire for the assessment of pediatric medicines (15). However, the results of the questionnaire indicated that most subjects found Infacort to be neutral with respect to smell and taste because subjects described it as “not good or bad” for smell on 86% of occasions, for feel in the mouth on 71% of occasions, and for taste on 79% of occasions. Only one subject described the taste as “very bad,” and this was on the two occasions with the higher doses.

Although there was a linear increment in systemic exposure to cortisol as the dose of Infacort was increased from 0.5 to 10 mg, this was not proportional to dose based on total serum cortisol concentrations. Cortisol is bound in plasma to both albumin and a specific cortisol binding protein. The latter binding is partially saturable over the range of therapeutic plasma concentrations of cortisol (11). Therefore, a more appropriate indication of systemic exposure is based on unbound serum cortisol concentrations. When correction was made for the predicted extent of plasma binding using mean binding data from the publication of Lentjes and Romijn (11), dose proportionality was evident across all doses of Infacort that were studied.

In conclusion, Infacort, a hydrocortisone formulation designed specifically for administration to infants and neonates, was shown to be easy to administer, well tolerated, neutral to taste, safe, and bioequivalent to conventional hydrocortisone tablets licensed for adults. This was a PK study; therefore, an efficacy phase II/III study is necessary to confirm that Infacort can optimize the treatment of neonates and children with adrenal insufficiency.

Acknowledgments

This work was funded by the European Commission, Project No. 281654 (FP7-HEALTH) and supported by GLATT GmbH, Germany, and Simbec Research Ltd, United Kingdom.

Registered EudraCT no.: 2013–000260–28.

Disclosure Summary: R.J.R., G.T., and M.W. are directors of Diurnal Ltd, and H.H., D.D., and D.E. are consultants to Diurnal Ltd. S.S., T.N.J., H.K., and O.B. have nothing to declare.

Abbreviations

 
• AUC_0-inf

  area under the curve from zero to infinity

 
• AUC_0-t

  area under the curve from zero sample to final sample

 
• CAH

  congenital adrenal hyperplasia

 
• CI

  confidence interval

 
• C_max

  maximum concentration

 
• PK

  pharmacokinetic

 
• t_max

  time of maximum concentration.

References