Development and clinical application of a stability-indicating chromatography technique for the quantification of diazoxide.

Diazoxide is a potential candidate for the treatment of transitional hypoglycaemia in infants. A clinical trial is currently underway to investigate whether low-dose oral diazoxide is beneficial for severe or recurrent transitional neonatal hypoglycaemia (the NeoGluCO Study, registration ANZCTR12620000129987). The present study aimed to develop and validate the parameters for quantifying diazoxide from neonatal plasma samples, and to assess the stability of extemporaneously prepared diazoxide suspensions to support the NeoGluCO Study. To determine the plasma concentration of diazoxide, a protein precipitation mediated extraction protocol was developed, which demonstrated >94% diazoxide extraction recoveries from all samples. The method was linear over the range of 0.2-40 µg/mL (R2 > 0.9994) with a limit of quantification of 0.2 µg/mL. Accuracy of the method was within 97-106% with relative standard deviation < 6% for all samples. Diazoxide-plasma samples were stable for up to three months at -20 °C and up to 48 h when stored in the auto-sampler. Samples were stable for up to two freeze-thaw cycles, with further cycles compromising stability of diazoxide in plasma. The developed method was applied to determine chemical stability of the extemporaneously prepared diazoxide suspensions. These were stable at both 2-8 °C and 25 °C/60% RH, with 98% of diazoxide remaining after 35 days in both storage conditions. Diazoxide was successfully quantified from plasma collected from six neonates enrolled in the NeoGluCO Study, using the developed protocol. Overall, an efficient and reproducible extraction protocol was developed and validated for the estimation of diazoxide from human plasma.

Rectal Bioavailability of Amoxicillin from Hollow-Type Suppositories: Effect of Chemical Form of Amoxicillin.

Rectal drug administration could offer advantages in the delivery of medicines for children by avoiding swallowability issues, improving stability and enabling administration by caregivers. This study aimed to evaluate the rectal bioavailability of hollow-type suppositories (HTS) and understand the effect of two chemical forms of amoxicillin: amoxicillin sodium (AS) or amoxicillin trihydrate (AMT). HTS were prepared by incorporating a lipophilic core containing the antibiotic with a polyethylene glycol (PEG) shell. Formulations were characterised in vitro, and the absolute bioavailability was determined in a rabbit model, while drug-base interactions were evaluated using X-ray diffraction crystallography (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. The in vitro amoxicillin release from AMT HTS was delayed, taking 27.3 ± 4.9 h to release 50% drug compared with 1.7 h for the AS HTS, likely due to solubility differences between AMT and AS. The presence of orthorhombic AMT and anhydrous AS crystals in respective HTS was confirmed via XRD and DSC. PEG shells were able to protect the drug chemical stability when stored at 25 °C/60% RH. Despite the difference in their in vitro release rates, a similar rectal bioavailability was found in both forms of amoxicillin (absolute bioavailability 68.2 ± 6.6% vs. 72.8 ± 32.2% for AMT HTS and AS HTS, respectively; p = 0.9682). Both HTS formulations showed little or no irritation to the rectal mucosa following a single dose.

Rectal bioavailability of amoxicillin sodium in rabbits: Effects of suppository base and drug dose.

In this paper, rectal absorption and tissue tolerance of amoxicillin sodium (AS) suppositories prepared in a hydrophilic base, polyethylene glycol (PEG) or lipophilic base, Suppocire® NA 15 (SNA 15), were investigated. Following in vitro characterization, including drug distribution in the suppository bases, drug-base interactions and drug release, pharmacokinetics were investigated in rabbits to determine absolute bioavailability (F) at two dose levels (100 mg and 200 mg). Both types of suppositories were found uniform in weight and content. Powder X-ray diffraction (XRD) and differential scanning calorimetry indicated that AS existed as solid dispersion or anhydrous crystalline dispersion in both suppositories at different ratios without changing melting points of the bases. This was supported by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy conjugated with energy dispersive X-ray (SEM/EDX). In dissolution medium, melting and spreading of SNA 15 and dissolution of PEG suppositories accounted for their different drug release kinetics and mean dissolution time (MDT). A rapid and complete amoxicillin absorption (F close to 100%) with a double peak pharmacokinetic profile was observed alongside minimal signs of tissue irritation in rabbits treated with SNA 15 suppositories at both dose levels. In contrast, the F of amoxicillin from PEG suppositories was 59%, increasing to 77.3% as AS dose doubled from 100 mg to 200 mg, reflected in the slower release predominately controlled by erosion of the base. An in vitro - in vivo correlation was observed (MDT vs F; p < 0.01). AS was stable in SNA 15 suppositories at least for three months at 20 ± 0.2 °C. This research highlighted the advantages of SNA 15 suppositories over the PEG suppositories in providing rapid and complete rectal absorption of AS and tissue compatibility.

Simple and reliable extraction and a validated high performance liquid chromatographic assay for quantification of amoxicillin from plasma.

This study presents the development of an efficient extraction protocol for amoxicillin from plasma with improved solubility and stability using pH control. Solubility and stability of amoxicillin in commonly used extraction solvents were determined using a newly developed stability-indicating high-performance liquid chromatography (HPLC) method. Following this, protein precipitation (PP) mediated sample purification protocol was developed and validated along with the HPLC method for the extracted amoxicillin from rabbit plasma. The protocol was applied in a pharmacokinetic study in rabbits. A five-fold increase in solubility and two-fold increase in stability of amoxicillin was found by addition of acetate buffer (0.1 M, pH 5.0) in acetonitrile. PP mediated extraction protocol containing acetate buffer-acetonitrile (1:18 v/v) resulted in an extraction recovery of >80% for all the samples. The HPLC assay following extraction was found linear (R2   >0.9999) over the range of 0.2-20 µg/mL with a lower limit of quantification of 0.2 µg/mL. The accuracy of the quality control samples was found between 97-115% and the relative standard deviation (RSD) was found to be below 6% for all samples. The samples were stable in the mobile phase (pH 5.0) for 72 h post-extraction. Amoxicillin-spiked plasma samples were found stable for up to three freeze-and-thaw cycles but, nearly 50% samples had degraded following storage for two months at -20 °C. Pharmacokinetic analysis indicated a half-life of amoxicillin of nearly 1 h following intravenous injection in rabbits, which is similar to that in humans. Thus, a simple and repeatable, extraction protocol was developed using pH control for quantification of amoxicillin from plasma based on its physicochemical properties.

Advances in rectal drug delivery systems.

Drug delivery via the rectum is a useful alternative route of administration to the oral route for patients who cannot swallow. Traditional rectal dosage forms have been historically used for localized treatments including delivery of laxatives, treatment of hemorrhoids and for delivery of antipyretics. However, the recent trend is showing an increase in the development of novel rectal delivery systems to deliver drug directly into the systemic circulation by taking advantage of porto-systemic shunting. The present review is based on research studies carried out between years 1969-2017. Data for this review have been derived from keyword searches using Scopus and Medline databases. Novel rectal drug delivery systems including hollow-type suppositories, thermo-responsive and muco-adhesive liquid suppositories, and nanoparticulate systems incorporated into an appropriate vehicle have offered more control over delivery of drug molecules for local or systemic actions. In addition, various methods for in vitro-in vivo evaluation of rectal drug delivery systems are covered which is as important as the formulation, and must be carried out using appropriate methodology. Continuous research and development in this field of drug delivery may unleash the hidden potential of the rectal drug delivery systems.