A Bioequivalence Study of Two Oral Desmopressin Tablet Formulations

Dual thermal stabilizing effects of xanthan gums via glycosylation and hydrogen bonding and in vivo human bioavailability of desmopressin in orodispersible film

Desmopressin acetate (DDAVP), a nonapeptide drug, is easily destroyed by heat in the manufacturing process of orodispersible film (ODF). A new challenging study was conducted to improve thermal stability through glycosylation and hydrogen bonding using carbohydrate gums (agar, arabic gum, carrageenan, xanthan gum) using the solvent casting method. Among gum types, xanthan gum strongly showed dual stabilizing effects of DDAVP via covalent glycosylation and hydrogen bonding, minimizing total impurities and optimizing physicochemical properties of ODF under accelerated conditions for six months. The optimized ODF formulation (O-DDAVP ODF) at a DDAVP and xanthan gum ratio of 1:1.5 had a pharmaceutically equivalent dissolution profile as compared with a commercial 0.2 mg commercial Minirin® tablet in four different media: pH 1.2, pH 4.0, and pH 6.8 buffers and deionized water. Furthermore, O-DDAVP ODF showed in vivo bioequivalence to Minirin® tablets in healthy human volunteers. Glycosylation-oriented stabilization of peptide drug using pharmaceutically active excipients against thermal denaturation could be challenged to design patient-friendly ODF.

An Integrated Paediatric Population PK/PD Analysis of dDAVP: How do PK Differences Translate to Clinical Outcomes?

INTRODUCTION

The bioequivalence of two formulations of desmopressin (dDAVP), a vasopressin analogue prescribed for nocturnal enuresis treatment in children, has been previously confirmed in adults but not in children. In this study, we aimed to study the pharmacokinetics (PK) and pharmacodynamics (PD) of these two formulations, in both fasted and fed children, including patients younger than 6 years of age.

METHODS

Previously published data from one PK study and one PK/PD study in children aged between 6 and 16 years were combined with a new PK/PD study in children aged between 6 months and 8 years, and analysed using population PK/PD modelling. Simulations were performed to further explore the relative bioavailability of both formulations and evaluate current dosing strategies.

RESULTS

The complex absorption behaviour of the lyophilizate was modelled using a double input, linked to a one-compartmental model with linear elimination and an indirect response model linking dDAVP concentration to produced urine volume and osmolality. The final model described the observed data well and elucidated the complexity of bioequivalence and therapeutic equivalence of the two formulations. Simulations showed that current dosing regimens using a fixed dose of lyophilizate 120 μg is not adequate for children, assuming children to be in the fed state when taking dDAVP. A new age- and weight-based dosing regimen was suggested and was shown to lead to improved, better tailored effects.

CONCLUSIONS

Bioequivalence and therapeutic equivalence data of two formulations of the same drug in adults cannot be readily extrapolated to children. This study shows the importance of well-designed paediatric clinical trials and how they can be analysed using mixed-effects modelling to make clinically relevant inferences. A follow-up clinical trial testing the proposed dDAVP dosing regimen should be performed.

CLINICAL TRIAL REGISTRATION

This trial has been registered at www.clinicaltrials.gov (identifier NCT02584231; EudraCT 2014-005200-13).

Pediatric Pharmacology of Desmopressin in Children with Enuresis: A Comprehensive Review

Desmopressin is a synthetic analogue of the natural antidiuretic hormone arginine vasopressin. Over the years, it has been clinically used to manage nocturnal polyuria in children with enuresis. Various pharmaceutical formulations of desmopressin have been commercialized for this indication-nasal spray, nasal drops, oral tablet and oral lyophilizate. Despite the fact that desmopressin is a frequently prescribed drug in children, its use and posology is based on limited pediatric data. This review provides an overview of the current pediatric pharmacological data related to the different desmopressin formulations, including their pharmacokinetics, pharmacodynamics and adverse events. Regarding the pharmacokinetics, a profound food effect on the oral bioavailability was demonstrated as well as different plasma concentration-time profiles (double absorption peak) of the desmopressin lyophilizate between adults and children. Literature about maturational differences in distribution, metabolism and excretion of desmopressin is rather limited. Regarding the pharmacodynamics, formulation/dose/food effect and predictors of response were evaluated. The lyophilizate is the preferred formulation, but the claimed bioequivalence in adults (200 µg tablet and 120 µg lyophilizate), could not be readily extrapolated to children. Prescribing the standard flat-dose regimen to the entire pediatric population might be insufficient to attain response to desmopressin treatment, whereby dosing schemes based on age and weight were proposed. Moreover, response to desmopressin is variable, whereby complete-, partial- and non-responders are reported. Different reasons were enumerated that might explain the difference in response rate to desmopressin observed: different pathophysiological mechanisms, bladder capacity and other predictive factors (i.e. breast feeding, familial history, compliance, sex, etc.). Also, the relapse rate of desmopressin treatment was high, rendering it necessary to use a pragmatic approach for the treatment of enuresis, whereby careful consideration of the position of desmopressin within this treatment is required. Regarding the safety of the different desmopressin formulations, the use of desmopressin was generally considered safe, but additional measures should be taken to prevent severe hyponatremia. To conclude the review, to date, major knowledge gaps in pediatric pharmacological aspects of the different desmopressin formulations still remain. Additional information should be collected about the clinical relevance of the double absorption peak, the food effect, the bioequivalence/therapeutic equivalence, the pediatric adapted dosing regimens, the study endpoints and the difference between performing studies at daytime or at nighttime. To fill in these gaps, additional well designed pharmacokinetic and pharmacodynamic studies in children should be performed.

Clinical study shows improved absorption of desmopressin with novel formulation

PURPOSE

To create improved pharmaceutical formulations for nasal and sublingual administration of desmopressin and investigate their pharmacokinetic profiles in comparison with a commercial nasal liquid spray and finally to evaluate the volunteers' opinions on the different dosage forms.

METHODS

Both formulations were based on the characteristics of interactive mixtures. The nasal powder spray was produced by a rotary evaporator technique with sodium starch glycolate as carrier material and the sublingual tablet by direct compression after dry mixing with mannitol as carrier. The clinical study was an open-label, randomised cross-over pharmacokinetic study in healthy volunteers.

RESULTS

The nasal powder formulation gave a threefold increase in the absorption, unaltered time to maximum plasma concentration and a tendency to lower variability in the amount absorbed compared with the liquid spray. The powder was reported to be more irritating than the liquid but was still well accepted by the volunteers. The tablet did not improve the uptake of desmopressin, likely because of a poor disintegration sublingually.

CONCLUSIONS

The nasal powder formulation is a promising new dosage form for the delivery of desmopressin and other compounds. The sublingual tablet has a beneficial means of production and may be further developed by decreasing its disintegration time.