Awie F. Kotzé

Oral Delivery of Peptide Drugs

A wide variety of peptide drugs are now produced on a commercial scale as a result of advances in the biotechnology field. Most of these therapeutic peptides are still administered by the parenteral route because of insufficient absorption from the gastrointestinal tract. Peptide drugs are usually indicated for chronic conditions, and the use of injections on a daily basis during long-term treatment has obvious drawbacks. In contrast to this inconvenient and potentially problematic method of drug administration, the oral route offers the advantages of self-administration with a high degree of patient acceptability and compliance. The main reasons for the low oral bioavailability of peptide drugs are pre-systemic enzymatic degradation and poor penetration of the intestinal mucosa. A considerable amount of research has focused on overcoming the challenges presented by these intestinal absorption barriers to provide effective oral delivery of peptide and protein drugs. Attempts to improve the oral bioavailability of peptide drugs have ranged from changing the physicochemical properties of peptide molecules to the inclusion of functional excipients in specially adapted drug delivery systems. However, the progress in developing an effective peptide delivery system has been hampered by factors such as the inherent toxicities of absorption-enhancing excipients, variation in absorption between individuals, and potentially high manufacturing costs. This review focuses on the intestinal barriers that compromise the systemic absorption of intact peptide and protein molecules and on the advanced technologies that have been developed to overcome the barriers to peptide drug absorption.

Enhancement of nasal and intestinal calcitonin delivery by the novel Pheroid fatty acid based delivery system, and by N-trimethyl chitosan chloride.

Therapeutic peptides are highly potent and specific in their functions, but difficulties in their administration require parallel development of viable delivery systems to improve their bioavailability. In this study the potential of a novel lipid-based colloidal delivery system for improving the absorption of nasally and intestinally administered salmon calcitonin (sCT) was investigated. Two types of delivery vehicles based on Pheroid technology was prepared and characterized. Liposome-like bilayer vesicles had a mean diameter of 1.0 microm and microsponges were 1.6 microm. Doses of 10 IU/kg and 500 IU/kg bodyweight sCT were administered intranasally and intestinally to rats, respectively. The obtained absorption enhancement with Pheroid vesicles and Pheroid microsponges were also compared with the absorption enhancement obtained with N-trimethyl chitosan chloride (TMC). With the inclusion of 0.5% (w/v) TMC the maximum plasma concentration (C(max)) of sCT increased from 72.6+/-6.1 pg/ml to 478.5+/-6.1 pg/ml after nasal administration. Pheroid vesicles and Pheroid microsponges increased the C(max) values of sCT to 262.64+/-17.1 pg/ml and 202.66+/-28.6 pg/ml, respectively. The time to reach the maximum concentration (T(max)) was also significantly decreased from 35 min to approximately 14 min. Intestinal administration of Pheroid formulations increased the C(max) of sCT from 249.1+/-21.5 pg/ml to 386.2+/-45.5 and 432.1+/-18.9 pg/ml, respectively for Pheroid vesicles and Pheroid microsponges. TMC increased the C(max) of sCT to 738.9+/-277.1 pg/ml. TMC and Pheroid technology could offer the potential to significantly improve intranasal and intestinal absorption of sCT and reduce the variability in absorption.

In vivo/in vitro pharmacokinetic and pharmacodynamic study of spray-dried poly-(dl-lactic-co-glycolic) acid nanoparticles encapsulating rifampicin and isoniazid

Poly-(dl-lactic-co-glycolic) acid (PLGA) nanoparticles were prepared by a double emulsion solvent evaporation spray-drying technique and coated with polyethylene glycol (PEG 1% v/v). The PLGA nanoparticles had a small size (229±7.6 to 382±23.9nm), uniform size distribution and positive zeta potential (+12.45±4.53mV). In vitro/in vivo assays were performed to evaluate the pharmacokinetic (PK) and pharmacodynamic (PD) performance of these nanoparticles following nanoencapsulation of the anti-tuberculosis drugs rifampicin (RIF) and isoniazid (INH). The results demonstrated the potential for the reduction in protein binding of these drugs by protection in the polymer core. Furthermore, in vitro efficacy was demonstrated using Mycobacterium tuberculosis (M. tb.) (strain H37Rv). Sustained drug release over seven days were observed for these drugs following once-off oral administration in mice with subsequent drug distribution of up to 10 days in the liver and lungs for RIF and INH, respectively. It was concluded by these studies combined with our previous reports that spray-dried PLGA nanoparticles demonstrate potential for the improvement of tuberculosis chemotherapy by nanoencapsulation of anti-tuberculosis drugs.

Absorption of the novel artemisinin derivatives artemisone and artemiside: potential application of Pheroid™ technology

Artemisinins have low aqueous solubility that results in poor and erratic absorption upon oral administration. The poor solubility and erratic absorption usually translate to low bioavailability. Artemisinin-based monotherapy and combination therapies are essential for the management and treatment of uncomplicated as well as cerebral malaria. Artemisone and artemiside are novel artemisinin derivatives that have very good antimalarial activities. Pheroid™ technology is a patented drug delivery system which has the ability to entrap, transport and deliver pharmacologically active compounds. Pharmacokinetic models were constructed for artemisone and artemiside in Pheroid™ vesicle formulations. The compounds were administered at a dose of 50.0mg/kg bodyweight to C57 BL/6 mice via an oral gavage tube and blood samples were collected by means of tail-bleeding. Drug concentrations in the samples were determined using an LC/MS/MS method. There was 4.57 times more artemisone in the blood when the drug was entrapped in Pheroid™ vesicles in comparison to the drug only formulation (p < 0.0001). The absorption of artemiside was not dramatically enhanced by the Pheroid™ delivery system.

Nasal delivery of recombinant human growth hormone: In vivo evaluation with pheroid technology and N-Trimethyl chitosan chloride

PURPOSE It was the aim of this study to investigate the possible enhancement of the absorption of recombinant human growth hormone (rhGH) in the nasal cavity, in the presence of a polymeric absorption enhancer, N-trimethyl chitosan chloride (TMC) and a fatty acid-based delivery system, Pheroid. METHODS Two types of Pheroid formulations, Pheroid vesicles and Pheroid microsponges were characterized and evaluated with regard to particle size and morphology. In vivo bioavailability studies in rats were performed and the nasal bioavailability of Pheroid vesicles and Pheroid microsponges were compared relative to subcutaneous administration. The results were also compared with different N-trimethyl chitosan chloride (TMC) formulations, TMC H-L and TMC H-H, well studied absorption enhancers. RESULTS Pheroid vesicles and Pheroid microsponges showed a size distribution of approxiamately 2-3 microm and 3-4 microm for Pheroid vesicles and Pheroid microsponges respectively. Using specific RIA, the relative bioavailability of rhGH after comparison with subcutaneous injection was determined to be 38.9, 128.5, 39.9, 136.3, and 8.3 % for Pheroid microsponges, Pheroid vesicles, TMC H-H, TMC H-L and control group (intranasal rhGH alone), respectively. All the enhancers showed significant absorption enhancement (P < 0.05) with the highest effect observed with TMC H-L. CONCLUSIONS All the enhancers may have promising potential as safe and effective nasal absorption enhancers of rhGH.

Evaluation of the physical properties and stability of two lipid drug delivery systems containing mefloquine

Stability data is used to determine the change the product has undergone over a certain time period at specific temperatures. In the present study, the physical stability characterized by size, pH and entrapment efficacy of mefloquine loaded liposomes and Pheroid™ vesicles were investigated. Size was accurately determined by flow cytometry. Entrapment efficacy, after unentrapped drug was removed was successfully determined by UV-spectrophotometry. The formulations contained 0.5% (m/v) mefloquine and results showed that mefloquine interfered with the formation of lipid bilayer of the liposomes. Liposomes increased in size from 5.22±0.03 μm to 9.71±1.11 μm with accelerated stability and large aggregates were observed. A notable difference in stability testing of Pheroid™ vesicles was seen with no significant increase in size. Entrapment efficacy of 68.72±0.04% (5°C), 67.45±2.92% (25°C) and 67.45±2.92% (30°C) were obtained at the different storage conditions. With these findings the mefloquine loaded Pheroid™ vesicles are stable and should be used investigated for the possible increase in efficacy and bioavailability and decrease toxicity.

Formulation and evaluation of Pheroid vesicles containing mefloquine for the treatment of malaria

Mefloquine (MQ) is an antimalarial drug with high efficacy, often used in the treatment and chemoprophylaxis of malaria. However, it has low solubility in water, a long elimination half‐life (4 days), and is neurotoxic, which leads to unwanted side effects.

Intestinal drug absorption enhancers: synergistic effects of combinations

Although many absorption enhancers have been investigated, very few are used clinically. A need exists therefore for more effective absorption enhancers. The drug-absorption-enhancing effects of combinations of N-trimethyl chitosan chloride (TMC) with degrees of quaternization of 48 and 64%, dicarboxymethyl chitosan oligosaccharide, and chitosan lactate oligomer with monocaprin and melittin were compared to their individual performances using the in vitro Caco-2 cell model. Combining the absorption enhancers showed synergism in both the reduction of the transepithelial electrical resistance (TEER) and the enhancement of the transport of a macromolecular model compound across this intestinal epithelial cell layer. Lower concentrations of the absorption enhancers in the combination groups exhibited greater effects on the epithelial cells compared with the individual absorption enhancers.

Effect of moisture content, temperature and exposure time on the physical stability of chitosan powder and tablets

Abstract Context: Chitosan does not rank highly regarding its employment as tablet filler due to certain limitations. Undesirable properties that limit its utilization as excipient in solid dosage forms include its hydration propensity that negatively affects tablet stability, strength and disintegration. Objective: The objective of this study was to investigate the physical stability of chitosan powder, mixtures, granules and tablets under accelerated conditions such as elevated temperatures and humidity over different periods of time. Methods: Selected physico-chemical properties of pure chitosan powder, physical mixtures of chitosan with Kollidon® VA64 (BASF, Ludwigshafen, Germany), chitosan granules, as well as tablets were evaluated under conditions of elevated humidity and temperature. Results and discussion: The physical stability of chitosan tablets exhibited sensitivity towards varying exposure conditions. It was furthermore evident that the presence of moisture (sorbed water) had a marked influence on the physical stability of chitosan powder and tablets. It was evident that the presence of Kollidon® VA64 as well as the method of inclusion of this binder influenced the properties of chitosan tablets. The physical stability of chitosan powder deteriorated to a greater extent compared to that of the chitosan tablets, which were subjected to the same conditions. Conclusion: It is recommended that tablets containing chitosan should be stored at a temperature not exceeding 25 °C as well as at a relatively low humidity (<60%) to prevent deterioration of physical properties. Direct compression of chitosan granules which contained 5%w/w Kollidon® VA64 produced the best formulation in terms of physical stability at the different conditions.

In vitro activity of Pheroid vesicles containing antibiotics against Plasmodium falciparum

The macrolide antibiotics, erythromycin and azithromycin, have been studied for their potential antimalarial activity, but only modest activity has been demonstrated. In this study, we investigated the enhancement of the efficacy of these antibiotics in combination with a patented lipid-based drug delivery system, Pheroid technology. A chloroquine resistant strain of Plasmodium falciparum (RSA11) was incubated with the formulations for a prolonged incubation time (144 h). Drug efficacy assays were conducted by analyzing the histidine-rich protein II levels of the parasites. The effects of azithromycin and erythromycin were compared with other antibiotics and standard antimalarial drugs. The poor water soluble nature of the drugs led to the formation of micro scale Pheroid vesicles with average particle sizes of 72.76±10.73 μm for azithromycin and 100.62±29.27 μm for erythromycin. The IC50 values of erythromycin and azithromycin alone and entrapped in Pheroid vesicles decreased statistically significant (P⩽0.05). Prolonged exposure was also statistically meaningful (P⩽0.05), although it seems that exposure need not exceed 96 h. Pheroid vesicles also proved successful in decreasing the IC50 values of doxycycline, tetracycline and triclosan. Pheroid vesicles containing antibiotics could prove successful as a malaria treatment option.