Smart pills for gastrointestinal diagnostics and therapy

Ingestible smart pills have the potential to be a powerful clinical tool in the diagnosis and treatment of gastrointestinal disease. Though examples of this technology, such as capsule endoscopy, have been successfully translated from the lab into clinically used products, there are still numerous challenges that need to be overcome. This review gives an overview of the research being done in the area of ingestible smart pills and reports on the technical challenges in this field.

Singularities of nevirapine metabolism: from sex-dependent differences to idiosyncratic toxicity

Nevirapine (NVP) is a first-generation non-nucleoside reverse transcriptase inhibitor widely used for the treatment and prophylaxis of human immunodeficiency virus infection. The drug is taken throughout the patient's life and, due to the availability of an extended-release formulation, it is administered once daily. This antiretroviral is one of the scarce examples of drugs with prescription criteria based on sex, in order to prevent adverse reactions. The therapy with NVP has been associated with potentially life-threatening liver and idiosyncratic skin toxicity. Multiple evidence has emerged regarding the formation of electrophilic NVP metabolites as crucial for adverse idiosyncratic reactions. The formation of reactive metabolites that yield covalent adducts with proteins has been demonstrated in patients under NVP-based treatment. Interestingly, several pharmacogenetic- and sex-related factors associated with NVP toxicity can be mechanistically explained by an imbalance toward increased formation of NVP-derived reactive metabolites and/or impaired detoxification capability. Moreover, the haptenation of self-proteins by these reactive species provides a plausible link between NVP bioactivation and immunotoxicity, further supporting the relevance of this toxicokinetics hypothesis. In the current paper, we review the existing knowledge and recent developments on NVP metabolism and their relation to NVP toxicity.

Antiretroviral considerations in HIV-infected patients undergoing bariatric surgery

WHAT IS KNOWN AND OBJECTIVE

With the advent of antiretroviral therapy and the resultant decrease in mortality among adults living with human immunodeficiency virus (HIV), there is now an increased incidence of obesity and obesity-related comorbidities in these patients. Bariatric surgery is becoming an increasingly common treatment option for patients who are classified as clinically obese. There are limited data regarding the use of antiretroviral therapy in patients who have undergone bariatric surgery. The purpose of this review was to evaluate the available literature regarding antiretroviral therapy and pharmaceutical properties in this special population.

METHODS

Literature review was performed through PubMed, utilizing search terms of bariatric surgery, sleeve gastrectomy, Roux-en-Y, HIV infection, obesity and antiretroviral. Direct medical information requests to antiretroviral pharmaceutical manufacturers were also completed.

RESULTS

Several case series and case reports have been published which demonstrate minimal risk of complications and maintenance of virologic suppression in the vast majority of patients. Bariatric surgery appears to be an effective mechanism for assistance in controlling obesity in patients infected with HIV; however, numerous factors may impact the safe and effective use of antiretroviral therapy.

WHAT IS NEW AND CONCLUSION

Due to the physiologic changes and postoperative management following bariatric surgery, evaluation of the patients' medication regimens must be considered and several factors should be taken into account when choosing the appropriate antiretroviral regimen for these patients. Furthermore, communication between the patients' surgeon, HIV provider and a clinical pharmacist should occur prior to surgery to ensure the patient is optimized to achieve the best outcome including maintaining virologic suppression.

Pharmacokinetic analysis of nevirapine extended release 400 mg once daily vs nevirapine immediate release 200 mg twice daily formulation in treatment-naïve patients with HIV-1 infection

BACKGROUND

VERxVE data showed non-inferior virologic efficacy with extended release nevirapine (NVP-XR) dosed 400 mg once daily (QD) versus immediate release nevirapine (NVP-IR) 200 mg twice daily in a double-blind, non-inferiority study in treatment-naïve HIV-1-positive patients.

OBJECTIVE

To study the pharmacokinetics (PK) of the NVP formulations and identify possible associations with demographic factors.

METHODS

Patients with viral load ≥1000 copies/mL and CD4+ count > 50- <400 cells/mm³ (males) and >50- <250 cells/mm³ (females) at screening received NVP-IR 200 mg QD during a 14-day lead-in and were then stratified by baseline viral load and randomized to NVP-XR or -IR. NVP trough concentrations at steady state (SS) (C_pre,ss,N) were measured up to week 48 for all participating patients. In a PK sub-study, SS parameters - AUC_0-24, C_max, C_min, and peak-to-trough fluctuation were obtained and analyzed with relative bioavailability assessed at week 4 by plasma collection over 24 h.

RESULTS

Trough concentrations were stable from week 4 to week 48 for all patients (n = 1011) with both formulations, with NVP-XR/IR ratios of 0.77-0.82. Overall, 49 patients completed the PK sub-study: 24 XR and 25 IR. NVP-XR showed less peak-to-trough fluctuation (34.5%) than IR (55.2%), and lower AUC_0-24, C_min, C_max, and trough concentrations than IR. However, no effect of SS trough concentrations was found on the virologic response proportion at least up to 1000 ng/mL. No significant association was found between NVP PK and gender, race, and viral load.

CONCLUSION

These data suggest NVP-XR achieves lower but effective NVP exposure compared with NVP-IR.

Absorption sites of orally administered drugs in the small intestine

INTRODUCTION

In pharmacotherapy, drugs are mostly taken orally to be absorbed systemically from the small intestine, and some drugs are known to have preferential absorption sites in the small intestine. It would therefore be valuable to know the absorption sites of orally administered drugs and the influencing factors. Areas covered:In this review, the author summarizes the reported absorption sites of orally administered drugs, as well as, influencing factors and experimental techniques. Information on the main absorption sites and influencing factors can help to develop ideal drug delivery systems and more effective pharmacotherapies. Expert opinion: Various factors including: the solubility, lipophilicity, luminal concentration, pKa value, transporter substrate specificity, transporter expression, luminal fluid pH, gastrointestinal transit time, and intestinal metabolism determine the site-dependent intestinal absorption. However, most of the dissolved fraction of orally administered drugs including substrates for ABC and SLC transporters, except for some weakly basic drugs with higher pKa values, are considered to be absorbed sequentially from the proximal small intestine. Securing the solubility and stability of drugs prior to reaching to the main absorption sites and appropriate delivery rates of drugs at absorption sites are important goals for achieving effective pharmacotherapy.

Biopharmaceutical Evaluation and CMC Aspects of Oral Modified Release Formulations

This article discusses the range of outcomes from biopharmaceutical studies of specific modified release (MR) product examples in preclinical models and humans. It touches upon five major biopharmaceutical areas for MR drug products: (1) evidence for regional permeability throughout the GI tract, (2) susceptibility to food-effect, (3) susceptibility to pH-effect, (4) impact of chronopharmacology in designing MR products, and (5) implications to narrow therapeutic index products. Robust bioperformance requires that product quality is met through a thorough understanding of the appropriate critical quality attributes that ensure reliable and robust manufacture of a MR dosage form. The quality-by-design (QbD) aspects of MR dosage form design and development are discussed with the emphasis on the regulatory view of the data required to support dosage form development.

A HAART-Breaking Review of Alternative Antiretroviral Administration: Practical Considerations with Crushing and Enteral Tube Scenarios

Selection of an appropriate antiretroviral regimen for the patient infected with human immunodeficiency virus can be challenging, as various considerations must be taken into account including viral resistance mutations, patient comorbidities, drug interactions, and the potential for drug-related adverse effects and toxicities. Treatment is further complicated when a clinical scenario arises requiring an alteration in the dosage form. Factors ranging from dysphagia to administration through an enteral feeding tube can affect decisions regarding antiretroviral dosage forms. Limited pharmacokinetic data exist regarding the alteration of antiretroviral medications from their original form. Bioavailability may vary substantially between dosage forms, which can lead to unpredictable drug concentrations. Supratherapeutic or subtherapeutic antiretroviral drug concentrations can result in increased toxicity, virologic failure, or the emergence of drug resistance. We performed a systematic literature search to review the available antiretroviral literature on the modification of solid dosage forms as well as alternative routes of administration of oral antiretroviral agents and their application to clinical practice.

Formulation, optimization, and evaluation of self-emulsifying drug delivery systems of nevirapine

Background:

The aim of the present study was to formulate and optimize the self-emulsifying drug delivery systems (SEDDS) of nevirapine (NVP) by use of 2² factorial designs to enhance the oral absorption of NVP by improving its solubility, dissolution rate, and diffusion profile. SEDDS are the isotropic mixtures of oil, surfactant, co-surfactant and drug that form oil in water microemulsion when introduced into the aqueous phase under gentle agitation.

Materials and Methods:

Solubility of NVP in different oils, surfactants, and co-surfactants was determined for the screening of excipients. Pseudo-ternary phase diagrams were constructed by the aqueous titration method, and formulations were developed based on the optimum excipient combinations with the help of data obtained through the maximum micro emulsion region containing combinations of oil, surfactant, and co-surfactant. The formulations of SEDDS were optimized by 2² factorial designs.

Results:

The optimum formulation of SEDDS contains 32.5% oleic acid, 44.16% tween 20, and 11.9% polyethylene glycol 600 as oil, surfactant, and co-surfactant respectively. The SEDDS was evaluated for the following drug content, self-emulsification time, rheological properties, zeta potential, in vitro diffusion studies, thermodynamic stability studies, and in vitro dissolution studies. An increase in dissolution was achieved by SEDDS compared to pure form of NVP.

Conclusion:

Overall, this study suggests that the dissolution and oral bioavailability of NVP could be improved by SEDDS technology.

Bioavailability of nevirapine in rats after oral and subcutaneous administration, in vivo absorption from gastrointestinal segments and effect of bile on its absorption from duodenum

Nevirapine is a non-nucleoside reverse transcriptase inhibitor of human immunodeficiency virus type-1. The usual dosing regimen is 200 mg twice/day. Reducing the dosing frequency would significantly improve treatment adherence and quality of life of patients. To study new forms of administration, it is necessary to do pre-clinical studies and know the absorption characteristics of nevirapine in laboratory animals. However, there are no studies about its bioavailability in rats and hardly any about its pharmacokinetic. The objectives of this study were to describe the pharmacokinetics of nevirapine in rats after intravenous, oral and subcutaneous administration, to assess its absorption by different regions of the gastrointestinal tract and to evaluate the effect of bile on its intestinal absorption. Nevirapine was well absorbed after oral and subcutaneous administration and the bioavailability estimated in rats (91% for both administration routes) was practically equal to that reported in humans (91-93%) after oral administration of therapeutic doses. Nevirapine was absorbed from the duodenum, ileum and colon, while absorption from the stomach was very low. The rate of absorption was in the order: duodenum>ileum>colon>stomach. The presence of bile in the duodenum increased the absorption rate of nevirapine.

In vitro-in vivo correlation for nevirapine extended release tablets

An in vitro-in vivo correlation (IVIVC) for four nevirapine extended release tablets with varying polymer contents was developed. The pharmacokinetics of extended release formulations were assessed in a parallel group study with healthy volunteers and compared with corresponding in vitro dissolution data obtained using a USP apparatus type 1. In vitro samples were analysed using HPLC with UV detection and in vivo samples were analysed using a HPLC-MS/MS assay; the IVIVC analyses comparing the two results were performed using WinNonlin. A Double Weibull model optimally fits the in vitro data. A unit impulse response (UIR) was assessed using the fastest ER formulation as a reference. The deconvolution of the in vivo concentration time data was performed using the UIR to estimate an in vivo drug release profile. A linear model with a time-scaling factor clarified the relationship between in vitro and in vivo data. The predictability of the final model was consistent based on internal validation. Average percent prediction errors for pharmacokinetic parameters were <10% and individual values for all formulations were <15%. Therefore, a Level A IVIVC was developed and validated for nevirapine extended release formulations providing robust predictions of in vivo profiles based on in vitro dissolution profiles.