International Journal of Pharmaceutics (v.283, #1-2)
TITLE PAGE (EDI BOARD) (iii).
A review of the development of Respimat® Soft Mist™ Inhaler by R. Dalby; M. Spallek; T. Voshaar (1-9).
Respimat® Soft Mist™ Inhaler (SMI) is a new generation inhaler from Boehringer Ingelheim developed for use with respiratory drugs. The device functions by forcing a metered dose of drug solution through a unique and precisely engineered nozzle (the uniblock), producing two fine jets of liquid that converge at a pre-set angle. The collision of these two jets generates the soft mist. The soft mist contains a high fine particle fraction of approximately 65 to 80%. This is higher than aerosol clouds from conventional portable inhaler devices, such as pressurised metered dose inhalers (pMDIs) and dry powder inhalers (DPIs). In addition, the relatively long generation time of the aerosol cloud (approximately 1.5 s) facilitates co-ordination of inhalation and actuation – a major problem with pMDIs. These features, together with the slow velocity of the soft mist, result in larger amounts of the drug reaching the lungs and less being deposited in the oropharynx compared with either pMDIs or DPIs. Generation of the soft mist from Respimat® SMI is purely mechanical, so propellants are not necessary. The innovative design of Respimat® SMI, using water-based drug formulations, ensures patients receive consistent and reliable doses of the drug with each actuation. The device was initially tested in scintigraphic lung deposition studies and produced encouraging results when compared with the chlorofluorocarbon-based pMDI (CFC-MDI). Subsequent clinical studies have confirmed that Respimat® SMI is effective and safe in delivering bronchodilators to patients with asthma or chronic obstructive pulmonary disease.
Keywords: Respimat® Soft Mist™; Inhaler (SMI); Lung deposition; Fine particle fraction; Aerosol; Obstructive lung disease; Inhaler device;
New protamine quantification method in microtiter plates using o-phthaldialdehyde/N-acetyl-l-cysteine reagent by Dirk Lochmann; Sylvia Stadlhofer; Jörg Weyermann; Andreas Zimmer (11-17).
Protamine is a well-known excipient in pharmaceutics. It represents a peptide consisting of exclusive aliphatic amino acids, hence it cannot be quantified by UV-spectroscopy (λ max 280 nm). A new and sensitive quantification method based on the derivatisation of protamine with ortho-phthaldialdehyde (OPA) in the presents of 2-mercaptoethanol (ME) or N-acetyl-l-cysteine (NAC) in basic aqueous solution using 96-well microtiter plates are introduced in this report. The resulting isoindol derivatives reveal a fluorescence excitation (maximum λ ex 345 nm) and emission (maximum λ em 450 nm) spectra. Derivatives of OPA/NAC reagent were found to be useful for protamine quantification in pharmaceutical nanoparticle preparation containing DNA. A sufficient stability of the isoindol derivatives was shown. It was possible to determine protamine free base, protamine sulphate and protamine chloride with limits of detection less than 1.1 μg/ml.
Keywords: Protamine; OPA/NAC reagent; Quantification; Microtiter plate; Ortho-phthaldialdehyde; N-acetyl-l-cysteine;
Experimental designed optimisation and stability evaluation of dry suspensions with artemisinin derivatives for paediatric use by M. Gabriëls; J. Plaizier-Vercammen (19-34).
There is a great need for oral anti-malaria preparations especially for small children, which are easy to administer and keep their stability under tropical conditions. The purpose of this work was therefore to develop a dry suspension, containing one of the artemisinin derivatives, namely artesunate, artemether and dihydroartemisinin using fast wetting suspending agents, i.e. xanthan gum and Avicel® CL611. For the optimisation of these two variables, namely the suspending agent’s content, a Doehlert design was applied. Via preliminary tests on sedimentation behaviour, the limits of both products were determined, respectively 0.1–0.4% (w/v) and 1.0–2.5% (w/v). As responses, sedimentation as a function of time, viscosity and price of the suspension, were evaluated.The stability tests of the reconstituted suspensions showed bad results for artesunate, even when the pH was adapted. In contrast, dihydroartemisinin showed only 10% degradation within 10 days and artemether was stable at least 21 days. Practically the last one was able to foresee a chemically and physically stable suspension at least during the administration period (5 to 7 days) and was therefore selected for further optimisation concerning taste and appearance. Based on the results of selection tests for the colourant, sweetener and taste masking agent, the following composition was proposed for a suitable dry powder with artemether (AM) as active compound to prepare 100 ml reconstituted suspension: AM 300 mg, Avicel® CL611 2 g, xanthan gum 200 mg, crystalline saccharose 35 g, citric acid monohydrate 150 mg, Nipagine® 80 mg, Nipasol® 20 mg, sodium saccharinate 250 mg, tutti-frutti 250 mg and Sunset yellow 10 mg.
Keywords: Dry powder for paediatric suspension; Artemether; Artesunate; Dihydroartemisinin; Colouring agent; Tast masking agents;
Implantable technology for long-term delivery of nalmefene for treatment of alcoholism by Lauren C. Costantini; Sofie R. Kleppner; Joseph McDonough; Marc R. Azar; Raj Patel (35-44).
Pharmacotherapy treatment for alcoholism is limited by poor compliance, adverse effects, and fluctuating drug levels after bolus administration. A long-term delivery system would improve upon these limitations. The current study describes the characterization of a sustained release implant containing nalmefene, an opioid antagonist, for treatment of alcoholism. Nalmefene was blended with ethylene vinyl acetate (EVA), extruded into 2.8 mm × 27 mm rods, and coated with EVA to optimize release. In vitro release was determined by HPLC, and in vivo release characteristics after subcutaneous implantation into rats were determined by LC–MS/MS analyses. Extrusion produced rods containing 80.09 ± 6.0 mg nalmefene. In vitro release was high from the uncoated rods, and they were depleted of drug fairly quickly; however EVA coatings maintained release over longer periods. The 25 wt.% coated rods provided in vitro release of 0.36 mg/day/rod, and in vivo release of 0.29 mg/day/rod over 6 months, and showed dose-dependent nalmefene plasma concentrations (one rod: 3.33 ± 0.56 ng/ml, three rods: 10.19 ± 2.31 ng/ml). After explantation, nalmefene plasma concentrations were undetectable by 6 h. A sustained release nalmefene rod provides 6 months of drug with no adverse effects.
Keywords: Nalmefene; Alcohol dependence; Alcoholism; Long-term delivery; Ethylene vinyl acetate;
In vitro transdermal delivery of the major catechins and caffeine from extract of Camellia sinensis by Rachel J. Batchelder; Richard J. Calder; Chris P. Thomas; Charles M. Heard (45-51).
The aim of this study was to investigate the feasibility of the transdermal delivery of catechins and caffeine from green tea extract. Drug-in-adhesive patches containing 1.35, 1.03, 0.68, and 0.32 mg cm−2 green tea extract were formulated and the dissolution of (−)-epigallocatechin gallate (EGCg), (−)-epigallocatechin (EGC) and (−)-epicatechin (EC) from these was determined. Transdermal delivery was determined across full thickness pig ear skin from saturated solutions of green tea extract in pH 5.5 citrate–phosphate buffer, polyethylene glycol 400 and a 50:50 mixture of the citrate phosphate buffer and polyethylene glycol in addition to patches containing 1.35 mg cm−2 green tea extract. Dissolution experiments indicated first order release which was dose dependent in respect of the loading level, although the amounts permeated were not always proportional to the amounts in the formulation. The highest percentage permeation of EGCg was found to be from the patch formulation. EGCg, EGC and EC were all successfully delivered transdermally from saturated solutions and adhesive patches containing green tea extract in this study. There was some evidence for the dermal metabolism of EGCg, but after 24 h 0.1% permeated from the patches containing 1.35 mg cm−2 green tea extract. This was equivalent to the percentage absorbed after intragastric administration of green tea extract in rats. In addition, the concentration of EGCg in the Franz cell receptor chamber after 24 h permeation from the 0.9 cm diameter patch containing 1.35 mg cm−2 was within the range of C max plasma levels achieved after oral dosing of 2.2–4.2 g m−2 green tea extract. Caffeine was also delivered at concentrations above those previously reported.
Keywords: Tea; Catechins; Polyphenols; Transdermal delivery; Drug-in-adhesive patch;
Kinetics of liposome-encapsulated hemoglobin after 25% hypovolemic exchange transfusion by V.D. Awasthi; D. Garcia; R. Klipper; W.T. Phillips; B.A. Goins (53-62).
Liposome-encapsulated hemoglobin (LEH) is being developed as an oxygen therapeutic. In this work, we evaluated a neutral formulation of PEGylated LEH for its circulation and distribution properties in rodent models of 25% hypovolemic exchange transfusion. About 25% of blood in rats and rabbits was exchanged with LEH that had been previously labeled with 99mTc radionuclide. The distribution of 99mTc-LEH was followed by gamma camera imaging and intermittent blood sampling during 48 h, and counting the tissue-associated radioactivity after necropsy at 48 h. On the basis of circulation kinetics, the half-life of 99mTc-LEH in blood was 30 and 39.8 h in rats and rabbits, respectively. Apart from blood, major organs of accumulation of LEH after 48 h included liver (rats, 10.3% and rabbits, 5.4% of injected dose) and spleen (rats, 2.4% and rabbits, 0.8% of injected dose). The results demonstrate that LEH circulates for a prolonged time after administration and that the animals tolerate at least 25% of blood exchange without any distress. Subsequent to the enhanced uptake in the RES, the rats clear LEH from the circulation faster than the rabbits.
Keywords: Liposome-encapsulated hemoglobin; Blood substitute; Exchange transfusion; Liposomes;
Precision and detection limit of quality test for amorphous drug in powder X-ray diffractometry by Shinichi Kitahara; Tsuneo Ishizuka; Toshihiro Kikkoji; Rieko Matsuda; Yuzuru Hayashi (63-69).
This report puts forward a method of powder X-ray diffractometry to estimate the precision and detection limit of the crystalline component in an amorphous drug. Cefditoren pivoxil (CP) was employed as a model drug. The major error source of the measurement at low crystal contents is shown to be the random noise in a diffraction pattern (halo pattern) of the amorphous material. For the analysis of the noise, the obstructive halo pattern should be eliminated from the observed pattern. The subtraction of the observed halo pattern from another one derived from the same material, extracts the random noise alone, although the noise is amplified by 2 times. The noise in the powder X-ray diffractometry was identified as the white noise. On the basis of the stochastic properties of the extracted noise and signal parameters (peak area) of CP, the relative standard deviations (R.S.D.) of the area measurements of the crystalline diffraction peaks were estimated over a wide range of crystal contents without repeated experiments. The detection limit was determined such that the crystal content at detection limit produced 30% R.S.D. of the measurements. The R.S.D. and detection limit obtained from FUMI theory were in good agreement with the results from the repeated measurements.
Keywords: Powder X-ray diffraction; Detection limit; Precision; FUMI theory;
Ultrasonically controlled release and targeted delivery of diclofenac sodium via gelatin magnetic microspheres by Muniyandy Saravanan; Kesavan Bhaskar; Gomathinayagam Maharajan; Kalathil Sadasivan Pillai (71-82).
In the present work, an attempt was made to target diclofenac sodium to its site of action through magnetic gelatin microspheres. The gelatin magnetic microspheres loaded with 8.9% w/w of diclofenac sodium and 28.7% w/w of magnetite were formulated by emulsification/cross-linking with glutaraldehyde. The formulated microspheres were characterized by particle size distribution, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction and in vitro release studies. The in vivo distribution and targetability of gelatin magnetic microspheres after i.v. administration were studied in rabbits. The formulated microspheres were below 5 μm and spherical in nature as evidenced by the SEM photographs. DSC and X-ray diffraction studies revealed the absence of drug–polymer interaction. Encapsulated diclofenac sodium was released slowly more than 18 days. Application of sonication, as external stimuli to enhance drug release, during release study, has slightly increased the release rate. The formulated microspheres were injected intravenously after keeping a suitable magnet near the target area. The quantity of drug available at the target and non-target area was determined by HPLC. About 5.5% of injected dose localized near the target organ. Majority of injected dose was recovered from lungs, spleen and liver indicating localization of microspheres in these organs. Further studies are required to improve the targeting efficiency of gelatin microspheres by modifying surface properties to overcome phagocytosis and by selecting suitable particle size to avoid the entrapment of microspheres in non-target organs.
Keywords: Gelatin magnetic microspheres; Diclofenac sodium; In vivo distribution of magnetic microspheres; Controlled and targeted drug delivery;
Deviation from linearity of drug solubility in ethanol/water mixtures by Stephen G. Machatha; Pilar Bustamante; Samuel H. Yalkowsky (83-88).
A new empirical function that describes the deviation from linearity of solubility of a drug in an ethanol/water matrix is applied to the experimental data for 51 compounds. The proposed model is a more accurate predictor of the co-solvent solubility profile than a general third order polynomial with the same number of parameters. Both the root mean square error and average absolute error for the proposed model are significantly lower than those of existing models. The model also accurately predicts the fraction of co-solvent that gives maximum solubility (f max).
Keywords: Deviation from linearity; Solubility in an ethanol/water matrix; Maximum solubility;
Effect of plasticization on heparin release from biodegradable matrices by L.P. Tan; S.S. Venkatraman; P.F. Sung; X.T. Wang (89-96).
Heparin-loaded polymer films of poly-l-lactide (PLLA) and poly-l-lactide-co-glycolide (PLLGA) as well as poly-dl-lactide-co-glycolide (PLGA) were produced. A plasticizer, PEG, was added to the polymers. It was found that the release profile in general consisted of a burst effect, a diffusion-controlled phase and a degradation-controlled phase. The plasticizer accelerated the onset of degradation in all cases, but its effect on the release profile differed significantly depending on the polymer. The plasticizer depressed the burst effect for PLLA, and accelerated the kinetics of the diffusion-controlled phase. For the PLLGA 80/20, however, the plasticizer had no significant effect on the release profile or kinetics. We explain these observations in terms of hydrophilicity and crystallinity effects.
Keywords: Local delivery; Biodegradable films; Stent; Heparin;
Characterization of perivascular poly(lactic-co-glycolic acid) films containing paclitaxel by John K. Jackson; Janet Smith; Kevin Letchford; Kelly Anne Babiuk; Lindsay Machan; Pierre Signore; William L. Hunter; Kaiyue Wang; Helen M. Burt (97-109).
The objectives of this study were to investigate the use of poly(lactic-co-glycolic acid) (PLGA) for the formulation of paclitaxel loaded films and to characterize these films for potential application as perivascular “wraps” to prevent restenosis. Films were manufactured from PLGA blended with either methoxypolyethylene glycol (MePEG) or a diblock copolymer composed of poly(d,l-lactic acid)-block-methoxypolyethylene glycol, PDLLA-MePEG (diblock) by solvent evaporation on teflon discs. Elasticity was determined by gravimetric stress/strain analysis. Thermal analysis was determined using differential scanning calorimetry (DSC). Changes in film composition and degradation in aqueous media were determined using gel permeation chromatography (GPC). Paclitaxel release from films was measured by incubation of the films in phosphate buffered saline (PBS) with drug analysis by HPLC methods. The addition of MePEG or diblock to PLGA caused a concentration dependent increase in the elasticity of films, due to plasticizing effects. DSC analysis showed that MePEG and diblock caused a concentration dependent decrease in the glass transition temperature (T g) of PLGA indicating miscibility of the polymers. When placed in aqueous media, more than 75% of MePEG dissolved out of the PLGA films within 2 days, whereas diblock partitioned slowly and in a controlled manner out of the films. Paclitaxel release from PLGA/MePEG films was very slow with less than 5% of the encapsulated drug being released over 2 weeks. The addition of 30% diblock to paclitaxel loaded PLGA films caused a substantial increase (five- to eight-fold) in the release rate of paclitaxel. PLGA films containing 30% diblock and either 1% or 5% paclitaxel were partially or completely degraded following perivascular implantation in rats.
Keywords: Perivascular drug delivery; Biodegradable polymers; Paclitaxel; Poly(lactic-co-glycolic acid); Films;
ATR-FTIR characterization of transport properties of benzoic acid ion-pairs in silicone membranes by Vimon Tantishaiyakul; Narubodee Phadoongsombut; Wibul Wongpuwarak; Jatupit Thungtiwachgul; Damrongsak Faroongsarng; Kamonthip Wiwattanawongsa; Yon Rojanasakul (111-116).
A novel technique based on Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to study the transport of benzoic acid ion-pairs/salts in silicone membranes. The benzoic acid ion-pairs were prepared using various counter-ions with different degrees of lipophilicity, e.g. triethylamine (TA), diethylamine (DE), tert-butylamine (t-BA), 2-amino-2-methyl-propanol (AMP), and 2-amino-2-methyl-propanediol (AMPD). Silicone membrane, treated or untreated with propylene glycol (PG), was placed on the surface of a ZnSe crystal and the transport solution was applied to the upper surface of the membrane. A mathematical model, based on Fick's second law describing the build up of permeant concentration at the membrane/crystal interface with time was applied to determine diffusion coefficients. Absorption due to the acid (1700 cm−1) or benzoate anion (1555 cm−1) was observed at different regions without the interference from PG or silicone membrane. Benzoate anion, a charged species, was observed to permeate the membrane. The permeation of benzoate anion from sodium benzoate and polar ion-pairs of AMP and AMPD was very low in contrast to their high-saturated concentrations in PG as compared to the t-BA ion-pair. This indicated that benzoate anion preferentially permeates the membrane as an ion-pair rather than a single anion; otherwise its permeation should correspond to its concentration in PG instead of the lipophilicity of the ion-pairs. Additionally, the diffusion coefficient values of benzoic acid and benzoate anions through the treated and untreated membranes were not statistically different.
Keywords: Benzoic acid; ATR-FTIR; Ion-pair; Permeation; Silicone membrane;
Grouping solvents by statistical analysis of solvent property parameters: implication to polymorph screening by Chong-Hui Gu; Hua Li; Rajesh B Gandhi; Krishnaswamy Raghavan (117-125).
The success rate of discovering new polymorphs by crystallization from solution may be increased if solvents with diverse properties are used during initial polymorph screening. In this study, eight solvent parameters, including hydrogen bond acceptor propensity, hydrogen bond donor propensity, polarity/dipolarity, dipole moment, dielectric constant, viscosity, surface tension and cohesive energy density (equal to square of solubility parameter), of 96 solvents were collected. Using the cluster statistical analysis of the parameters, these 96 solvents were separated into 15 solvent groups. Such solvent groups may provide guidelines for the judicious choice of solvents with diverse properties for polymorph screening.
Keywords: Cluster analysis; Polymorph screening; Solvent group; Solvent parameter;