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UDP-glucuronosyltransferases (UGTs), located in the endoplasmic reticulum of liver cells, are an important family of enzymes, responsible for the biotransformation of several endogenous and exogenous chemicals, including therapeutic drugs. However, the phenomenon of 'latency', i.e., full UGT activity revealed by disruption of the microsomal membrane, poses substantial challenges for predicting drug clearance based on in vitro glucuronidation assays. This work introduces a microfluidic reactor design comprising immobilized human liver microsomes to facilitate the study of UGT-mediated drug clearance under flow-through conditions. The performance of the microreactor is characterized using glucuronidation of 8-hydroxyquinoline (via multiple UGTs) and zidovudine (via UGT2B7) as the model reactions. With the help of alamethicin and albumin effects, we show that conducting UGT metabolism assays under flow conditions facilitates in-depth mechanistic studies, which may also shed light on UGT latency.

Continuous manufacturing methods offer economic and quality advantages when compared with batch manufacturing methods. In continuous manufacturing, one requires real time assurance of quality of product via the implementation of PAT tools. This study focuses on an in-line near-infrared (NIR) spectroscopic method for determining the drug content of powder mixtures and tablets during a continuous tableting process. Tablets consisting of acetaminophen (20–30%), lactose (69.07–78.93%) and magnesium stearate (0.93–1.07%) were prepared in a continuous direct compression line that consisted of two loss-in-weight feeders, one for acetaminophen and one for premixed lactose and magnesium stearate, and a continuous mixer followed by a rotary tablet press. NIR spectroscopy was applied to the continuous mixer and tablet press to perform a 100% product check at full tableting speed. The UV-spectrophotometric method was used as an off-line reference method to determine the acetaminophen content in the samples. The powder mixture and tablet samples were taken during the process for the calibration of continuous mixer and tablet press, respectively. For the continuous mixer, model creation with the PLS method yielded R-Square and RMSEC (root mean square error of calibration) values of 0.975% and 0.56%, respectively. For the tablet press, the corresponding R-Square and RMSEC values were 0.943% and 0.75%, respectively. A test run demonstrated good predictability in the estimation of the API content in the powder mixtures and tablets during the continuous tableting process. For the continuous mixer and tablet press, the RMSEP (root mean square error of prediction) values were 0.96% and 1.37%, respectively. This study demonstrates that an NIR instrument capable of fast spectra acquisition can be a valuable tool for the in-line monitoring of the continuous mixing and tableting processes.

The purpose of the present study was to develop novel cyclodextrin-containing sublingual formulations of cannabinoids. Complexation of model cannabinoids, Delta(9)-tetrahydrocannabinol (THC) and cannabidiol (CBD), with randomly methylated beta-cyclodextrin (RM-beta-CD) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD), were studied by the phase-solubility method. Due to better complexation efficiency, RM-beta-CD was selected for further studies. Solid THC/RM-beta-CD and CBD/RM-beta-CD complexes were prepared by freeze-drying. The dissolutions of both THC and CBD in the presence and absence of RM-beta-CD were determined. THC was selected for in vivo studies: the pharmacokinetics of THC after both sublingual and oral administrations of ethanolic THC and THC/RM-beta-CD complex solutions were studied in rabbits. The aqueous solubility of CBD and THC increased as a function of CD concentration, showing A(L)- and A(P)-type diagrams for HP-beta-CD and RM-beta-CD, respectively. Dissolution rates of THC/RM-beta-CD and CBD/RM-beta-CD complexes were significantly (p0.05) higher than those of plain THC and plain CBD, respectively. The absolute bioavailability (F) of THC decreased in the following order: sublingual THC/RM-beta-CD solution (F = 12.1+/-1.4%; mean+/-S.D.; n = 4)oral THC/RM-beta-CD solution (F = 4.0+/-6.0%)or = sublingual ethanolic THC solution (F = 3.8+/-2.8%)oral ethanolic THC solution (F = 1.3+/-1.4%). These results demonstrate that RM-beta-CD increases both the aqueous solubility and dissolution rate of these cannabinoids, making the development of novel sublingual formulation possible. These results also suggest that the sublingual administration of a THC/RM-beta-CD complex substantially increases the bioavailability of THC in rabbits.

Surface-eroding biodegradable polymers can provide many advantages in drug delivery, such as controllable and zero-order drug release. Photocrosslinkable poly(ester anhydride)s are a recently developed family of surface-eroding polymers with readily modifiable oligomer chemistry allowing tailoring of polymer properties. For example, in vivo release rate of peptide from photocrosslinked poly(ester anhydride)s can be controlled by oligomer hydrophobicity. In this study, X-ray microtomography (micro-CT) was used to gain a deeper understanding on internal structure, polymer erosion and drug release mechanisms of photocrosslinked poly(ester anhydride)s. Micro-CT is non-destructive and able to provide quantitative and qualitative information on the 3D structure of the sample in micrometer resolution. Photocrosslinked poly(ester anhydride) samples with varying drug loading degrees (propranolol HCl 0%, 10% and 60% w/w) and hydrophobicity (with and without 12-carbon alkenyl chain) were prepared. The samples, both freshly prepared and exposed to buffer solution for varying durations were characterized by micro-CT. The results showed that drug release from photocrosslinked poly(ester anhydride)s was primarily controlled by the surface erosion. However, drug diffusion had also a significant role in drug release from less hydrophobic samples with very high (60% w/w) drug loading degrees. In conclusion, micro-CT is a valuable tool in the characterization of surface-eroding polymers.

The aim of the study was to develop enzyme sensitive polymers for pharmaceutical applications. Thus, 2,2'-bis(2-oxazoline)-linked poly-epsilon-caprolactone (PCL-O) polymers were synthesized by using epsilon-caprolactone precursors with different molecular weights (M(n): 1500, 3900, 7500 and 12,000g/mol), and the effects of PCL block length on enzymatic degradation and erosion (weight loss) of PCL-O films were studied. Solvent cast PCL and PCL-O films were incubated (22 days) in the presence of pancreatin (1%, pH 7.5), with and without enzyme inhibitors. In the absence of enzyme inhibitors, surface erosion of the PCL-O films occurred during incubation, and the erosion of the PCL-O films increased in parallel with a decrease in the PCL block length. The presence of the lipase inhibitors, paraoxon-ethyl and tetrahydrolipstatin delayed the weight loss of the PCL-O films. These results indicate that lipase was mainly responsible for the enzymatic erosion of the PCL-O films. In comparison, practically no weight loss of the PCL or the PCL-O films was observed in phosphate buffer (pH 7.4) (28 days incubation). The results demonstrate that the studied epsilon-caprolactone based poly(ester-amide)s are enzyme sensitive polymers whose erosion rate can be controlled by the PCL block length.

Chronic use of non-steroidal anti-inflammatory drugs may reduce the risk or delay the onset of Alzheimer's disease. To date, only limited information exists on the brain distribution of these drugs. The objective of this study was to determine the absolute brain delivery of ibuprofen by using constant in vivo infusion in rats. Ibuprofen was infused to steady-state concentrations both in plasma and brain tissue. Ibuprofen levels in plasma and brain tissue were measured by RP-HPLC after the plasma and the brain samples were purified by protein precipitation and solid phase extraction, respectively. Results indicate that both plasma and brain concentrations reached steady-state within 6 h, and that the brain to plasma ratio of ibuprofen was only 0.02. Thus, limited brain penetration prevents the possible use of ibuprofen in treating or preventing neurodegenerative disorders such as Alzheimer's disease.

Phosphate esters of arachidonylethanolamide (AEA) and R-methanandamide were synthesized and evaluated as water-soluble prodrugs. Various physicochemical properties (pKa, partition coefficient, aqueous solubility) were determined for the synthesized phosphate esters. The chemical stability of phosphate esters was determined at pH 7.4. In vitro enzymatic hydrolysis rates were determined in 10% liver homogenate, and in a pure enzyme-containing (alkaline phosphatase) solution at pH 7.4. The intraocular pressure (IOP) lowering properties of R-methanandamide phosphate ester were tested on normotensive rabbits. The phosphate promoiety increased the aqueous solubility of the parent compounds by more than 16 500-fold at pH 7.4. Phosphate esters were stable in buffer solutions, but rapidly hydrolyzed to their parent compounds in alkaline phosphatase solution (t1/2<

In the present study, poly (epsilon -caprolactone) (PCL) was modified by introducing oxamide groups into PCL (PCL-O). The degradation (decrease in molecular weight) and erosion (weight loss) of PCL and PCL-O films were studied in PBS (pH 7.4, USP XXIV, 37 degrees C, 26 weeks incubation). The release rates of guaifenesin (M(w) 198.2), griseofulvin (M(w) 352.8), timolol (M(w) 332.4), sodium salicylate (M(w) 160.1) and FITC-dextran (M(w) 4400) from PCL and PCL-O preparations (solvent cast films, compression-molded plates, midi injection-molded rods and microparticles) were examined in PBS (pH 7.4, 37 degrees C). The degradation rate of PCL-O film was faster than that of PCL film while no erosion was observed for either film. When compared to the corresponding drug release from PCL films, the release rates of low molecular weight drugs (M(w)or =352.8) from PCL-O films were comparable, their releases from both films following closely square-root-of-time kinetics. These results indicate that the oxamide groups had no substantial effect on the release of the low molecular weight drugs. The exception was sodium salicylate which was released faster from PCL-O film. However, FITC-dextran release was notably faster from PCL-O microparticles than from those made of PCL. FITC-dextran release was a combination of diffusion and polymer degradation and thus, the faster degradation of PCL-O enhanced the release of FITC-dextran. In conclusion, the effects of the oxamide groups on drug release profiles were dependent on the drug release mechanisms.

Drug-carrier particle interactions greatly affect the detachment of drug from the carrier in inhalation powders. In this study, a novel multiple dose, reservoir-based Taifun was used as a dry powder inhaler, and the effects of carrier physical properties were evaluated on the pulmonary deposition of budesonide, along with physical stability of the inhalation powder. In this study, untreated commercial preparation of alpha-lactose monohydrate, highly amorphous spray dried lactose, crystallized spray dried lactose, Flowlac-100 and Flowlac-100 mixed with crystalline micronized lactose were used as carriers. Dry powder formulations were prepared by the suspension method, where the budesonide-carrier ratio was 1:15.1 (w/w). Carriers and formulations were initially characterized, and again after 1 month's storage at 40 degrees C/75% RH. The physical properties of the carriers strongly affected the pulmonary deposition of budesonide and the physical stability of the inhalation powder. Initially, amorphous contents of the carriers were 0-64%, but spontaneous crystallisation of the amorphous lactose occurred during storage and, thus all carriers were 100% crystalline after storage. When compared to an untreated alpha-lactose monohydrate, the highly amorphous spray dried lactose and Flowlac-100 did not improve aerosol performance of the inhalation powder. When crystalline spray dried lactose was used as a carrier, the highest RF% values were achieved, and RF % values did not alter during storage but the emitted budesonide dose was lower than the theoretical dose. When Flowlac-100 mixed with crystalline micronized lactose was used as a carrier, the emitted budesonide dose was close to the theoretical dose, and high RF % values were achieved but these changed during storage.

The synthesis and preliminary evaluation of novel alkyl and acyloxymethyl esters of etidronic acid as etidronate prodrugs is reported. Tetramethyl ester of etidronic acid was found be isomerized at pH 7.4 and P–C–P bridge was rearranged to P–C–O–P. This unwanted process was prevented via acylation of the bridging carbon’s alcohol group. Acylation showed to be stable if one or more phosphonic OH– groups were substituted. However, when none of the phosphonic OH– groups were substituted, the acylation was chemically hydrolysed and the parent drug was released. This finding was successfully applied in the design of tetrapivaloyloxymethyl ester of acetylated etidronic acid which released etidronic acid via enzymatic (first step) and chemical (second step) hydrolysis in liver homogenate. However, the corresponding tri-substituted pivaloyloxymethyl ester having adequate water-solubility and lipophilicity (log Papp 0.6 at pH 7.4), is probably the most potential prodrug candidate reported to enhance the oral bioavailability of etidronate.

Ocular absorption of pilocarpine and many other ophthalmic drugs can be improved by prodrug derivatization. For stability and solubility reasons basic prodrugs must be formulated at acidic pH, which may affect the corneal drug permeability. We studied the effects of pH on in vitro permeation of pilocarpine, pilocarpic acid benzyl diester prodrugs [O-propionyl (I) and O-valeryl (II)] and O,O'-(1, 4-xylylene) bispilocarpic acid diester prodrugs [O,O'-diacetyl (III), O,O'-dipropionyl (IV) and O,O'-divaleryl (V)] through albino rabbit cornea. Reversed-phase high-performance liquid chromatography was used to assay pilocarpine and its prodrugs. The permeability coefficient for pilocarpine decreased more than three times, from 2. 8x10-6 cm/s to 0.9x10-6 cm/s, when the pH was decreased from 7.65 to 5.5. At pH 7.65 permeability of pilocarpine improved several fold with delivery as prodrugs. Acidic pH (5.5, 6.0) affected to a different extent the corneal permeability of pilocarpine given as prodrugs. Consequently, the rank order of the corneal permeabilities among the compounds was different at various pH values. The effect of pH was greatest (an order of magnitude) for prodrugs with intermediate lipophilicity (I, III, IV), while pH had only minor or no effect on permeability of the most lipophilic prodrugs (II, V). In conclusion, the effect of pH on pilocarpine delivery as prodrug is dependent on prodrug structure and the advantage gained with prodrugs relative to pilocarpine is dependent on formulation pH.

The ocular bioavailability of pilocarpine has been improved by bispilocarpic acid diesters but the ocular irritation associated with these prodrugs is the main limitation of their clinical usefulness. Pilocarpine prodrugs show amphiphilic lipid bilayer disrupting properties which partly contribute to the eye irritation. In the present study, the influence of complexation with hydrophilic β-cyclodextrin derivatives, 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and sulfobutyl ether β-cyclodextrin with an average degree of substitution of four (SBE4-β-CD), on pilocarpine prodrug-induced bilayer perturbation was investigated using rabbit erythrocyte hemolysis and calcein release from liposomes as test models. Bispilocarpic acid diesters form 1:1 and 1:2 complexes with HP-β-CD and 1:1 complexes with SBE4-β-CD at pH 7.4. Both β-CD derivatives decreased the surface activity of the prodrug solutions. The hemolytic activity and liposome disruption of prodrug-CD solutions were 3–10 times and 4–15 times lower than that of parent prodrug, respectively. The protecting effect of CDs was dependent on the apparent complexation constant of prodrug/CD complex which determines the active free prodrug concentration in CD solution. The present study shows that amphiphilic properties and lipid bilayer perturbing effects of pilocarpine prodrugs are reduced by complexing them with hydrophilic β-CD derivatives.