Sompol Prakongpan

Combination Chemotherapy and Photodynamic Therapy with Fab′ Fragment Targeted HPMA Copolymer Conjugates in Human Ovarian Carcinoma Cells

The biological activities of sequential combinations of anticancer drugs, SOS thiophene (SOS) and mesochlorin e6 monoethylenediamine (Mce6), in the form of free drugs, nontargeted N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer−drug conjugates, P-GFLG-Mce6 and P-GFLG-SOS (P is the HPMA copolymer backbone and GFLG is the glycylphenylalanylleucylglycine spacer), and Fab′-targeted HPMA copolymer−drug conjugates, P-(GFLG-Mce6)-Fab′ and P-(GFLG-SOS)-Fab′ (Fab′ from OV-TL16 antibodies complementary to CD47), were evaluated against human ovarian carcinoma OVCAR-3 cells. Mce6, SOS, P-GFLG-Mce6, P-GFLG-SOS, P-(GFLG-Mce6)-Fab′, and P-(GFLG-SOS)-Fab′, when used as single agents or in binary combination, exhibited cytotoxic activities against OVCAR-3 cells, as determined using a modified MTT assay. The binding and internalization of P-(GFLG-Mce6)-Fab′ and P-(GFLG-SOS)-Fab′ by OVCAR-3 cells were visualized by confocal microscopy and flow cytometry. The results confirmed an enhanced biorecognition by OVCAR-3 cells of Fab′-targeted HPMA copolymer conjugates over nontargeted conjugates. The median-effect analysis and the determination of the combination index (CI) were used to describe the drug interaction and quantify the synergism, antagonism, or additivity in anticancer effects. The sequential combinations of SOS+Mce6 and P-GFLG-SOS+P-GFLG-Mce6 displayed very strong synergism to synergism in the entire range of cell inhibition levels (fa = 0.5 − 0.95). The P-(GFLG-SOS)-Fab′+P-(GFLG-Mce6)-Fab′ exhibited a strong synergism for fa values up to about 0.85, but showed synergistic effect and nearly additive effect at fa = 0.9 and 0.95, respectively. These observations support the continuation of in vivo investigations of these conjugates for the treatment of ovarian cancer.

Development of sustained release theophylline pellets coated with calcium pectinate

Abstract We have produced cores containing theophylline, calcium acetate and microcrystalline cellulose by extrusion-spheronization and then applied a coating of calcium pectinate by interfacial complexation. After drying, the coatings were observed by scanning electron microspcopy to be 50–80 μm thick. The type of pectin used, the core size and the coating time all influenced the yield of theophylline in the coated cores. Theophylline release from the uncoated cores was rapid and linear with the square root of time. The in-vitro release of theophylline from the coated cores was tested in water, simulated gastric fluid USP minus pepsin (SGF) and a Tris buffer (pH 7.4). In general, release was essentially constant until 75–80% of the drug was released. The large coated cores released over a period of about 4 h and the small coated cores released over a period of 2 h. Although the coatings swelled more when they were rehydrated in the Tris buffer compared to water and SGF, theophylline release was similar in all the dissolution media. In particular, release was not increased by SGF as may have been expected from studies using a similar polysaccharide sodium alginate. Calcium pectinate coatings are easy to apply, do not require harsh conditions and may yield release profiles which are relatively independent of pH.

Effect of poly(lactide-co-glycolide) molecular weight on the release of dexamethasone sodium phosphate from microparticles

The objective of this study was to investigate the effect of poly(lactide-co-glycolide) (PLGA) molecular weight (Resomer® RG 502H, RG 503H, and RG 504H) on the release behavior of dexamethasone sodium phosphate-loaded microparticles. The microparticles were prepared by three modifications of the solvent evaporation method (O/W-cosolvent, O/W-dispersion, and W/O/W-methods). The encapsulation efficiency of microparticles prepared by the cosolvent- and W/O/W-methods increased from ∼50% to >90% upon addition of NaCl to the external aqueous phase, while the dispersion method resulted in lower encapsulation efficiencies. The release of dexamethasone sodium phosphate from PLGA microparticles (>50 µm) was biphasic. The initial burst release correlated well with the porosity of the microparticles, both of which increased with increasing polymer molecular weight (RG 504H > 503H > 502H). The burst was also dependent on the method of preparation and was in the order of dispersion method > WOW method > consolvent method. In contrast to the higher molecular weight PLGA microparticles, the release from RG 502H microparticles prepared by cosolvent method was not affected by volume of organic solvent (1.5–3.0 ml) and drug loading (4–13%). An initial burst of ∼10% followed by a 5-week sustained release phase was obtained. Microparticles with a size <50 µm released in a triphasic manner; an initial burst was followed by a slow release phase and then by a second burst.

Feasibility of Biowaiver Extension to Biopharmaceutics Classification System Class III Drug Products

BackgroundThe extension of biowaivers (drug product approval without a pharmacokinetic bioequivalence study) to drugs belonging to Class III of the Biopharmaceutics Classification System (BCS) is currently a subject of much discussion.ObjectivesTo assess the relationship between in vitro dissolution characteristics and in vivo absorption performance of immediate-release (IR) products containing cimetidine, a BCS Class III compound, in human subjects. To evaluate the feasibility and appropriateness of an extension of the biowaiver concept to BCS Class III compounds.Study design and participantsBCS-conform dissolution tests were carried out on ten marketed cimetidine products from Thailand and Germany, as well as cimetidine tablet formulations containing cimetidine 400mg manufactured by direct compression using methacrylate copolymer (Eudragit® RS PO) as a release-retarding agent to yield three batches with significantly different release profiles. Twelve healthy male subjects were enrolled in a randomised, open-label, single-dose schedule based on a five-way Williams’ design balanced for carryover effects. Subjects received the following treatments, with 1-week washout periods between: (i) Tagamet® 400mg tablet; (ii) 7.5% methacrylate copolymer cimetidine tablet; (iii) 15% methacrylate copolymer cimetidine tablet; (iv) 26% methacrylate copolymer cimetidine tablet; and (v) Tagamet® (300mg/2mL) intravenous injection. The area under the plasma concentration-time curve from 0 to 12 hours (AUC12) and AUC from time zero to infinity (AUC∞), peak plasma concentration (Cmax), absolute bioavailability (F) and mean residence time (MRT) were evaluated and statistically compared among formulations. In vitro-in vivo correlation (IVIVC) analysis was then applied to elucidate the overall absorption characteristics of each tablet formulation.ResultsThe release properties of the ten marketed cimetidine products were shown to comply with current US FDA criteria for rapidly dissolving drug products. As expected, the in vitro dissolution profiles of the cimetidine tablets containing different percentages of methacrylate copolymer differed considerably from one another. However, in vivo results showed no significant difference in AUC12, AUC∞, Cmax and F between the tablets manufactured with methacrylate copolymer and the innovator. The MRT values obtained from 26% methacrylate copolymer tablets were significantly longer than for the other two methacrylate copolymer formulations and the Tagamet® tablets. Furthermore, IVIVC analysis showed that the 26% methacrylate copolymer tablets exhibited dissolution rate-limited absorption, whereas the other formulations showed permeability rate-limited absorption.ConclusionThe results of the present study indicated that the absorption of cimetidine from IR tablets is, in general, limited by permeability rather than dissolution. IVIVC analysis demonstrated that only when the release was deliberately retarded (tablets containing 26% methacrylate copolymer), did the dissolution represent the rate-limiting step to drug absorption. On the in vitro side, it seems that 85% dissolution within 30 minutes, as currently required by the US FDA Guidance, is more than sufficient to guarantee bioequivalence of IR cimetidine products. For cimetidine and other BCS Class III drugs with a similar intestinal absorption pattern, application of the biowaiver concept seems to present little risk of an inappropriate bioequivalence decision.

Calcium pectinate gel coated pellets as an alternative carrier to calcium pectinate beads

A conventional method of using drug entrapped in calcium pectinate beads as sustained release drug delivery systems have long been suffering from too rapid an in-vitro release. An approach to solve this setback by the method of calcium pectinate gel (CPG) coated pellets was then initiated. The spherical theophylline pellets, which contain calcium acetate, were prepared using an extrusion-spheronization method and then coated with pectin solution, using an interfacial complexation process. An insoluble and uniform coating of CPG was formed around the pellets. The comparison was made between theophylline uncoated pellets, calcium pectinate beads and this developed method by the variation of coating time and the type of pectin. The results in simulated gastric fluid (SGF) and water showed that theophylline release from the coated pellets was slower than that from the beads. The time for 50% release of theophylline (t50) from the CPG coated pellets in water and SGF are greater than the uncoated cores and the conventional beads. These results suggested that the coated pellets system were able to retard the release of theophylline to a greater extent than the conventional method. Therefore, this approach has been successfully achieved.

Adverse Effect of Rifampin on Quinine Efficacy in Uncomplicated Falciparum Malaria

ABSTRACT The effects of adding rifampin to quinine were assessed in adults with uncomplicated falciparum malaria. Patients were randomized to receive oral quinine either alone (n = 30) or in combination with rifampin (n = 29). Although parasite clearance times were shorter in the quinine-rifampin-treated patients (mean ± standard deviation, 70 ± 21 versus 82 ± 18 h; P = 0.023), recrudescence rates were five times higher (n = 15 of 23; 65%) than those obtained with quinine alone (n = 3 of 25; 12%), P < 0.001. Patients receiving rifampin had significantly greater conversion of quinine to 3-hydroxyquinine and consequently considerably lower concentrations of quinine in their plasma after the second day of treatment (median area under the plasma drug concentration-time curve from day zero to day 7 = 11.7 versus 47.5 μg/ml · day, P < 0.001). Rifampin significantly increases the metabolic clearance of quinine and thereby reduces cure rates. Rifampin should not be combined with quinine for the treatment of malaria, and the doses of quinine should probably be increased in patients who are already receiving rifampin treatment.

Assessment of the neurotoxicity of oral dihydroartemisinin in mice

High doses of the oil-soluble antimalarial artemisinin derivatives artemether and arteether, given by intramuscular injection to experimental mammals, produce an unusual pattern of selective damage to brainstem centres predominantly involved in auditory processing and vestibular reflexes. We have shown recently, in adult Swiss albino mice, that constant exposure either from depot intramuscular injection of oil-based artemisinin derivatives, or constant oral intake carries relatively greater neurotoxic potential than other methods of drug administration. Using the same model, oral dihydroartemisinin suspended in water was administered once or twice daily at different doses ranging from 50 to 300 mg/kg/day for 28 days. The neurotoxic potential of the oral dihydroartemisinin was assessed and compared to that of oral artemether and artesunate. Oral artemether, artesunate, and dihydroartemisinin had similar neurotoxic effects with no significant clinical or neuropathological evidence of toxicity at doses below 200 mg/kg/day. These data indicate that once and twice daily oral administration of artemether, artesunate and dihydroartemisinin is relatively safe when compared to intramuscular administration of the oil-based compounds.

Acrylic Matrix Type Nicotine Transdermal Patches: In Vitro Evaluations and Batch-to-Batch Uniformity

Abstract Nicotine transdermal patches (NTPs) were fabricated using an acrylic pressure sensitive adhesive emulsion to form a transparent matrix film. An automated thin layer chromatography (TLC) plate scraper was used to control the thickness of the cast nicotine matrix film. The in vitro release behavior and permeation of nicotine across abdominal human epidermis (HE) from the NTPs was studied using United States Pharmacopeia (USP) dissolution apparatus 5 (paddle over disk) and modified Franz-diffusion cell, respectively. The release of nicotine from the NTPs showed a good linear correlation with the square root of time (R2>0.99). This indicated a matrix diffusion controlled-release mechanism. The surface morphology of the matrix of the NTP was uniform and nonporous before and after release, indicating that the dried adhesive nicotine matrix was a homogeneous single-phase film. Neither the nicotine content in the range 4.70–8.41% w/w nor the film thicknesses of the NTPs affected the apparent diffusion coefficient of nicotine in the acrylic matrix. A good relationship between the amount of nicotine permeated across the HE and the square root of time was also observed with R2>0.98. This study also showed that the NTPs provided a good delivery system with more than 65% of the nicotine delivery being controlled by the device. Moreover, the release of nicotine from six production batches met the criteria of USP 24. This finding presented a good potential of this method for upscaling to industrial manufacturing.

Permeation Studies Comparing Cobra Skin with Human Skin Using Nicotine Transdermal Patches

Cobra skin (Naja Naja Khaotia) was used as a barrier for an in vitro permeation study using nicotine. Fluxes of nicotine that permeated from Nicotinell ® through cobra skin (CS) taken from the head, body, and tail were 233.93 ± 16.08, 206.87 ± 19.00, and 211.26 ± 22.93 μg/cm2/hr1/2, respectively (n=6). This indicated no significant difference (p >. 05). Abdominal human epidermis (HE), obtained from cadavers, and the CS provided identical permeation kinetics for nicotine, which can be described by Mt = 4Mα=(Dt π L2)1/2. The mean flux of nicotine formulated as an acrylic transdermal patch that permeated through HE was 137.92 ± 67.79 μg/cm2/hr1/2 (4 specimens, n= 12), whereas that through CS was 180.13 ± 41.05 μg/cm2/hr1/2 (4 specimens, n= 15). The ratio of the fluxes of nicotine from formulated patches having three different nicotine contents using CS and HE was 1.22 to 1, respectively, for each of the patches irrespective of nicotine content. The coefficients of variation of the nicotine permeated were 22.79% and 49.15% for CS and HE, respectively, that is, a narrower variation of results was obtained with CS. This indicated that CS could be used for nicotine permeation studies.

Shed king cobra and cobra skins as model membranes for in-vitro nicotine permeation studies.

Shed king cobra skin (SKCS) and shed cobra skin (SCS) were investigated for use as barrier membranes, including some pre‐hydration factors, for in‐vitro nicotine permeation. Inter‐specimen variations in nicotine fluxes using shed snake skin were compared with those using human epidermis. Nicotine in the form of 1% w/v aqueous buffer solution at pH 5 and transdermal patches (dose 14 mg day−1) were used. The nicotine fluxes across the shed snake skin were not significantly affected (P > 0.05) by temperature and duration of hydration pre‐treatment. Scanning electron micrographs of SKCS and SCS revealed a remarkable difference in surface morphology, but the nicotine fluxes using both shed skins were not significantly different (P > 0.05). When compared with the results obtained using human epidermis, there were similarities in fluxes and permeation profiles of nicotine. Using nicotine solution, the nicotine permeation profiles of all membranes followed zero order kinetics. The amount of nicotine permeated provided good linearity with the square root of time over 24 h (R2 > 0.98) when using nicotine patches. The nicotine fluxes using SKCS and SCS had less inter‐specimen variation than those using human epidermis. The results suggest a potential use for SKCS or SCS as barrier membranes for in‐vitro nicotine permeation studies.