Release and Absorption Characteristics of Novel Theophylline Sustained-Release Formulations: In Vitro-in Vivo Correlation

Five new experimental sustained-release (SR) formulations of theophylline, T-l, T-l-A, T-2, T-2-A, and T-2-E, in a matrix tablet form with a protein were developed. The in vitro release of theophylline from these novel experimental formulations and two commercial (Theotrim and Theo-Dur) SR formulations, was studied for 2 hr immersed in simulated gastric fluid TS, followed by an additional 10 hr immersed in simulated intestinal fluid TS. Like Theotrim and Theo-Dur, theophylline release profiles from all the novel experimental formulations were smooth, controlled, and unaffected by changes in the pH and the proteolytic enzyme content of the incubation media. Pharmacokinetic evaluation of T-l, T-l-A, T-2-A, Theotrim, and Theo-Dur was carried out in five dogs and six healthy human volunteers under fasting conditions, using immediate-release aminophylline tablets as controls. Pharmacokinetic analysis by the Wagner–Nelson procedure revealed sustained-release absorption characteristics for all the formulations with the exception of the immediate release aminophylline tablet. For each of the formulations tested, the regression analysis results of the percentage of theophylline absorbed in dogs or humans against the mean percentage released in vitro, at the corresponding times, indicated a high correlation. These data imply that the in vivo release profiles under fasting conditions in the gastrointestinal tract of dogs and humans may be similar to those in the in vitro studies.     

盐酸维拉帕米脉冲控释片的研究

目的:制备适于临睡前服用、间隔4 h 后于次日凌晨释放出治疗药物的脉冲控释片。方法:以均匀设计优化盐酸维拉帕米压制包衣片的处方组成,体外溶出度测定、体内γ-闪烁扫描示踪考察药物释放滞后时间(T_lag) ,在家犬、人体内的药代动力学研究,考察脉冲控释片在体内控时效果。结果:均匀设计得出的多元线性回归方程优化筛选了控时3,4 ,5 h 的脉冲片处方,体外脉冲控时4 h 的IV 型脉冲片,在家犬体内和体外控时3 h 的III型脉冲片在受试者体内均实现给药后4 h 脉冲释放。结论:脉冲控释片仅改变了制剂的释药开始时间,而对药物的峰浓度、生物利用度等无影响,实现设计中的脉冲释放,为防治高血压的凌晨发作提供了良好的剂型选择。     

明目蒺藜丸联合聚乙烯醇滴眼液治疗干眼症的临床研究

目的 制备他达拉非片并考察其体内外释药特性。方法 以溶出度为评价指标,筛选他达拉非片各辅料用量及包衣增重。用相似因子（f₂）法比较自制制剂与参比制剂在0.5% SDS溶液、含0.5% SDS的0.1 mol/L的盐酸溶液、含0.5% SDS的pH 4.5醋酸钠缓冲液、含0.5% SDS的pH 6.8磷酸盐缓冲液中溶出曲线的相似性。比较二者在Beagle犬体内的药动学特征。结果 他达拉非片处方为他达拉非20 mg、乳糖50M 227.625 mg、羟丙基纤维素L 10.5 mg、交联羧甲基纤维素钠19.6 mg、SDS 0.525 mg、微晶纤维素M102 70 mg、硬脂酸镁1.75 mg,包衣增质量范围2%～4%。自制与参比制剂在4种溶出介质中的f₂均大于65,二者体外溶出行为相似。2种制剂在Beagle体内的药动学参数AUC_0~t、C_max、t_max均无显著性差异,自制他达拉非片的相对生物利用度为（101.67±8.99）%。结论 成功制备他达拉非片,其体外溶出和体内药动学行为与参比制剂相似。     

Development and in Vitro-in Vivo Evaluation of a Multiparticulate Sustained Release Formulation of Diltiazem

Purpose. To develop and evaluate the in vitro/in vivo performance of diltiazem sustained release pellets that were prepared by the Wurster column process. Methods. Pellets containing diltiazem were prepared by spraying a slurry of micronized diltiazem hydrochloride, pharmaceutical glaze and alcohol onto an appropriate mesh fraction of nonpareil seeds using the Wurster column. A two-step drug layering process was used to increase drug loading from 60% to 75%. The oven-dried diltiazem basic pellets were coated with eth-ylcellulose/dibutyl sebacate coating solution to yield diltiazem sustained release pellets. An open, randomized Latin square, three-way crossover clinical study was used to evaluate the in vivo performance of the coated product. Results. Altering the mesh fraction of the starting nonpareil seeds for this layering process was found to affect the release characteristics of drug from the pellets. An oven-drying step was required to stabilize the diltiazem basic pellets. The thicker the drug loading layer the longer the oven drying is needed to stabilize the pellets. The diltiazem sustained release pellets produced by these methods displayed sustained release dissolution profiles both in vitro and in vivo. Diltiazem basic pellets coated with a 0.6% ethylcellulose/dibutyl sebacate coating showed a different rate of absorption (lower C _max and higherT _max) and the same extent of absorption as compared to Cardizem^® tablets. Conclusions. Clinical data confirmed that this formulation approach is an effective means to produce a diltiazem sustained release product.     

Dosage Form Development, <Emphasis Type="BoldItalic">in Vitro</Emphasis> Release Kinetics,and <Emphasis Type="BoldItalic">in Vitro–in Vivo</Emphasis> Correlation for Leuprolide Released from an Implantable Multi-reservoir Array

Purpose Implanted multi-reservoir arrays improve dosing control relative to osmotic pumps or polymer depots. The limited reservoir volume requires concentrated formulations. This report describes the development of a stable solid phase formulation of leuprolide acetate for chronic in vivo delivery from a multi-reservoir microchip and examines the correlation between in vitro release kinetics and serum pharmacokinetics. Materials and Methods Concentrated formulations (>10% w/v) were prepared using small volume processing methods. Drug yield, release kinetics, and formulation stability were evaluated in vitro by HPLC. The correlation between in vitro and in vivo kinetic data was determined for a solid formulation by direct comparison of data sets and using absorption kinetics calculated from the Wagner–Nelson equation. Results High yield and the control of release kinetics by altering peptide formulation or reservoir geometry were demonstrated. Lyophilized leuprolide in a soluble solid matrix exhibited reproducible release kinetics and was stable (>95% leuprolide monomer) after 6 months at 37°C. A strong correlation was found between in vitro release kinetics and in vivo absorption by direct comparison of data sets and using the Wagner–Nelson absorption (slopes of 1.01 and 0.91; R² 0.99). Conclusions Reproducible releases of a stable solid leuprolide formulation from a multi-reservoir microchip were achieved in vitro. Chronic pulsatile release was subsequently performed in vivo. Comparison of in vitro and in vivo data reveals that pharmacokinetics were controlled by the rate of release from the device.     

口服布洛芬原位凝胶的制备及其在Beagle犬体内药代动力学研究

本文设计并制备了口服布洛芬原位凝胶(in situ gel systems for the oral delivery of ibuprofen，IBU-ISG)， 并对其在Beagle犬上药代动力学进行了研究。以去乙酰结冷胶和海藻酸钠为凝胶材料， 分别对此两种凝胶材料进行了单因素考察， 初步确定了辅料的用量。以成胶前的复合黏度值、 体外释放度等参数为评价指标， 采用正交设计法进行处方优化。优化的制剂处方为： 1.0%海藻酸钠、 0.5%去乙酰结冷胶、 0.21%枸橼酸钠和0.056%氯化钙。采用RP-HPLC法测定6只Beagle犬口服IBU-ISG和参比制剂(市售布洛芬混悬液)后不同时间血浆中布洛芬的浓度， 所得药代动力学参数T_max分别为(1.8±0.6)和(0.4±0.1) h， C_max分别为(29.2±7.6)和(37.8±2.2)μg·mL^-1， T_1/2分别为(2.3±0.5)和(2.0±0.9) h， AUC_0-t分别为(131.0±38.6)和(117.3±23.1)μg·mL^-1·h。结果表明， 采用去乙酰结冷胶和海藻酸钠二元骨架制备IBU-ISG可行。     

Comparative bioavailability: A new type ofin vitro-in vivo correlation exemplified by prednisone

The average time to reach half-maximal plasma concentration of prednisolone and the average plasma concentrations of prednisolone at 0.5 and 1 hr obtained from three crossover bioavailability studies, involving testing of commercially available 5-mg prednisone tablets, were highly correlated (r0.88) with parameters derived from in vitrotablet dissolution rates performed in the spin filter apparatus of Shah. The in vitroparameters were the times to dissolve 16% or 50% of the labeled amount of prednisone or the percent of the labeled amount of prednisone dissolved in 20 min in water at 37C. Such correlations may be useful in the setting of in vitrodissolution rate specifications for commencal prednisone tablets.Supported by Contract FDA 69-22, Food and Drug Administration, Washington, D.C., and in part by Public Health Service Grant 5-P11-GM15559.     

Effect of antacids on aspirin dissolution and bioavailability

The in vitrodissolution profile, in vitroand in vivobuffering characteristics, and single-dose bioavailability of various buffered aspirin tablet formulations were studied. Buffering agents,such as magnesium and aluminum hydroxides (formulations B and C) or magnesium carbonate and aluminum glycinate (formulation D), significantly increased the rate of aspirin dissolution from solid dosage forms as compared to an unbuffered tablet (formulation A). The extent of aspirin absorption was equivalent with all formulations;however, the faster rate of dissolution (t₅₀ and t₉₀)with buffered formulations resulted in earlier and higher peak concentration of salicylate compared to that with unbuffered formulation, following a two-tablet dose in the fasting state. A comparison of the in vivobuffer capacity of a four-tablet dose of formulations B and D was performed in the postcibal state at the time of maximal meal-induced acid secretion, using a radiotelemetry procedure for determination of pH. Formulation B prolonged the interval of elevation of intragastric pH > 3 for 32 min as compared to 12 min for D.     

Correlation of in Vitro Release Rate and in Vivo Absorption Characteristics of Four Chlorpheniramine Maleate Extended-Release Formulations

An in vitro/in vivo correlation was established for four formulations of chlorpheniramine maleate (histamine, H₁-blocker) extended-release tablets exhibiting different in vitro release rate characteristics. In vitro release rate data were obtained for 12 individual tablets of each formulation using the USP Apparatus 2, paddle stirrer at 50 rpm in 1000 ml of distilled water at 37.0 ± 0.5°C. Inspection of the individual and mean release rate data indicated that the in vitro release rate of chlorpheniramine maleate was consistent with the intended design of the four extended-release formulations. The in vivo bioavailability and pharmacokinetics of these formulations were evaluated in 24 healthy subjects under fasting conditions. Wagner Nelson analyses of the in vivo data revealed extended release absorption profiles for all four formulations. Linear regression analyses of the mean percentage of dose absorbed versus the mean in vitro release resulted in a statistically significant correlation (r ² > 0.98, P < 0.001) for each formulation. Qualitative rank-order correlations were observed among all combinations of in vitro and in vivo parameters. These data support a Level A correlation between the in vitro release rate profiles and the in vivo absorption for chlorpheniramine maleate determined under fasting conditions.     

In vitro-in vivo correlation and bioavailability studies of captopril from novel controlled release donut shaped tablet

A controlled release formulation of captopril which was coated and fabricated into a donut shaped tablet formulation, was investigated in rabbit for pharmacokinetic and in vitro-in vivo correlation studies. Coated donut shaped tablets were prepared and in vitro release was studied in simulated gastric fluid at three different RPMs. New Zealand albino male rabbits have been used as animal model for in vivo study. A sensitive and simple HPLC method was developed for the determination of captopril content in rabbit plasma. In vitro release studies showed that release patterns followed zero order for around 4 h. Single oral administration of coated donut shaped tablets in rabbit illustrated retained availability of captopril to the injected drug. Captopril content could pursue the same release pattern over the same time course in in vivo study. The in vivo-in vitro correlation coefficients obtained from point-to-point analysis were greater than 99% between concentrations at certain time points obtained from release study in simulated gastric fluid at different RPMs and HPLC analysis of rabbit's plasma. From the in vitro-in vivo correlation prediction it was evident that the coated donut shaped tablet is a good device for controlled delivery of captopril.     

Design and in vivo evaluation of an indapamide transdermal patch

The aim of the present study was to develop and evaluate a novel drug-in-adhesive transdermal patch system for indapamide. Initial in vitro experiments were conducted to optimize formulation parameters prior to transdermal delivery in rats. The effects of the type of adhesive and the content of permeation enhancers on indapamide transport across excised rat skin were evaluated. The results indicated that DURO-TAK^® adhesive 87-2852 is a suitable and compatible polymer for the development of transdermal drug delivery systems for indapamide. The final formulation contained 4% N-dodecylazepan-2-one, 6% l-menthol and 3% isopropyl myristate. For in vivo studies patch systems were administered transdermally to rats while orally administered indapamide in suspension was used as a control. The PK parameters, such as the maximum blood concentration (C_max), time to reach the peak blood concentration (T_max), mean residence time (MRT), area under the curve (AUC_0–t) and terminal elimination half-life (T_1/2) were significantly (p < 0.05) different following transdermal administration compared with oral administration. In contrast to oral delivery, a sustained activity was observed over a period of 48 h after transdermal administration. This sustained activity was due to the controlled release of drug into the systemic circulation following transdermal administration.     

芍药苷胃漂浮片的制备

目的 制备芍药苷胃漂浮片,优选芍药苷胃漂浮片的制备工艺。方法 采用湿法制粒压片制备芍药苷胃漂浮片,以漂浮性能和体外累积释放率为考查指标,采用单因素筛选及正交设计法,优化芍药苷胃漂浮片处方。结果 以HPMC K4M(20%)为骨架材料、NaHCO₃(15%)为起泡剂、PVPP(7%)为释放促进剂、乳糖200为填充剂制得的胃漂浮片能立即起漂,持续漂浮12 h以上,累积释放率达90%以上。结论 优选的芍药苷胃漂浮片达到了持续漂浮及缓慢释放的要求,可操作性强。     

Spray-Dried Amorphous Solid Dispersions of Simvastatin,a Low T<Subscript>g</Subscript> Drug: <Emphasis Type="Italic">In Vitro</Emphasis> and <Emphasis Type="Italic">in Vivo</Emphasis> Evaluations

Purpose To obtain free flowing, stable, amorphous solid dispersions (SDs) of simvastatin (SIM), a drug with relatively lower glass transition temperature (T_g) by spray drying technique, and to perform comparative in vivo study in rats, which could justify the improvement in rate and extent of in vitro drug release.Methods Dichloromethane suspensions of SIM either alone or in combination with PVP (1:1 or 1:2 parts by weight) were spray dried with proposed quantity of Aerosil 200 (1:1, 1:1:1, 1:2:2 parts by weight of SIM, Aerosil 200 and PVP, respectively). SDs were characterized initially in comparison with pure drug and corresponding physical mixtures in same ratios by drug content, saturation solubility, SEM, DSC, XRPD, IR, and in vitro drug release. SD 1:2:2 was further subjected to accelerated stability testing and checked for in vitro drug release and presence of crystallinity using DSC and XRPD. In addition, improvement in rate and extent of in vitro drug release from SD 1:2:2 was justified by in vivo study in rats.Results Combination of SD and surface adsorption techniques has been attempted to overcome the limitations of spray drying technique for amorphization of low T_g drugs. Based on powder characteristics, drug content, saturation solubility, and feasibility of processing into tablets; SD 1:2:2 was selected as the optimized formulation. During initial characterization, SEM, DSC, and XRPD analyses confirmed the presence of amorphous form in SD 1:2:2. IR spectroscopy revealed possibility of hydrogen bonding interaction between SIM and PVP in SDs. Also, there was dramatical improvement in rate and extent of in vitro drug release of SD 1:2:2. Insignificant decrease in dissolution was observed with no evidence of crystallinity during accelerated stability studies of SD 1:2:2. Moreover in vivo study in rats also justified the improvement in therapeutic efficacy of SD 1:2:2 over pure SIM.Conclusions Thus, present study demonstrates high potential of spray drying technique for obtaining stable amorphous SDs of low T_g drugs.     

Formulation,Bioavailability, and Pharmacokinetics of Sustained-Release Potassium Chloride Tablets

The release of potassium chloride incorporated into hydrogenated vegetable oil and hydroxypropyl methylcellulose matrix tablets was studied in vitro. The formulations containing 20% hydrogenated vegetable oil and hydroxypropyl methylcellulose showed a sustained-release profile comparable to that of a standard commercially available sustained-release preparation, containing 8 mEq potassium chloride embedded in a wax material. The formulated and standard sustained-release potassium chloride tablets were compared to a conventional enteric-coated potassium chloride tablet in 10 healthy subjects. Mean recoveries in 24-hr urine potassium levels from four dosage forms (after subtracting normal urine potassium excretion levels) were 76 ± 32% from hydroxypropyl methylcellulose, 95 ± 22% from hydrogenated vegetable oil-incorporated matrix tablets, 91 ± 29% from commercially available sustained-release tablets, and 97 ± 13% from enteric-coated tablets. There was no significant difference (P > 0.05) in the time to reach maximum excretion rates among the three sustained-release tablets. No significant adverse effect was experienced with any of the preparations.     

A comparative study of different release apparatus in generating in vitro–in vivo correlations for extended release formulations

The importance of hydrodynamics in the development of in vitro–in vivo correlations (IVIVCs) for a BCS Class II compound housed in a hydrophilic matrix formulation and for a BCS Class I compound housed in an osmotic pump formulation was assessed. In vitro release data were collected in media simulating the fasted state conditions in the stomach, small intestine and the ascending colon using the USP II, the USP III and the USP IV release apparatuses. Using the data collected with the USP II apparatus, the plasma profiles were simulated and compared with human plasma profiles obtained after administration of the same dosage forms to healthy fasted volunteers. Data obtained with the USP III and USP IV apparatuses were directly correlated with the deconvoluted human plasma profiles. In vitro hydrodynamics affected the release profile from the hydrophilic matrix. For both formulations, based on the values of the difference factor, all three apparatuses were equally useful in predicting the actual in vivo profile on an average basis. Although some hydrodynamic variability is likely with low solubility drugs in hydrophilic matrices, the hydrodynamics of USP II, III and IV may all be adequate as a starting point for generating IVIVCs for monolithic dosage forms in the fasted state.     

Controlled Release of Paracetamol from Amylodextrin Tablets: In Vitro and in Vivo Results

Amylodextrin is a suitable excipient for the design of solid controlled-release systems. The release of paracetamol from tablets containing 30% drug and 70% amylodextrin was studied in vitro and in vivo. In vitro dissolution profiles showed almost-constant drug release rates during 8 hr, when measured in 0.05 M buffer, pH 6.8. Peroral administration of the tablets to man showed almost-constant paracetamol plasma levels up to 14 hr, as compared to fast absorption and fast elimination of a reference paracetamol solution. The plasma profiles of eight volunteers demonstrated a small intersubject variability during the first day after tablet administration. Increasing variability and decreasing plasma levels during the second day were caused by excretion of tablets from the bodies. Cumulative input as a function of time showed near-zero-order drug release during the first day. The in vivo results indicate that amylodextrin tablets are not hydrolyzed by -amylase, present in the gastrointestinal tract.     

Bioavailability of pseudoephedrine from controlled release formulations in the presence of guaifenesin in human volunteers

A multiple-dose bioequivalence study with six healthy human volunteers was conducted. The bioavailability of an experimental controlled release tablet containg pseudoephedrine was compared with a marketed controlled release pseudoephedrine capsule in a three-way crossover study. Plasma samples, collected serially after oral drug administrtion, were analyzed for pseudoephedrine content using a specific HPLC method with UV detection. The bioavailability parameters, area under the concentration-time curve (AUC), maximum plasma concentraton C_max, and time to peak (T_max) were obtained from the plasma concentraton—time data. Additionally, model independent pharmacokinetic parameters were estimated. Analysis of variance of the data revealed no statistically significant differences between the test and the reference formulation. The presence of guaifenesin in the sustained release tablet did not influence pseudoephedrine bioavailability. The relative bioavailability of the tablet dosage form with respect to the capsule was found to be 100.8%. Classical and Westlake 95% confidence limits as well as the two one-sided t test, proposed by Schuirmann, and the Anderson—Hauck power analysis supported the inference that the two formulations demonstrated comparable bioavailability, even in the presence of guaifenesin. Using a non-linear regression program, it was found that the parmacokinetics of pseudoephedrine followed a simple one-compartment disposition model with no lag time. Additionally, an in vitro—in vivo correlation, based on the estimation of cumulative relative fraction absorbed, was developed between the absorption of pseudoephedrine in humans and the in vitro dissolution time.     

A single-dose comparison of the bioavailabilty of aluminium from two formulations of sucralphate in normal volunteers

The oral bioavailability of aluminium was compared after administration of 1 g sucralphate as either a tablet or a suspension (1 g/5 ml) in a crossover study in 16 healthy volunteers. Aluminium levels were detectable in all subjects pre-dose (21.4±8·8 μg 1^?1 before tablet; 21·4±7·4 μg 1^?1 before suspension) and there was a measurable increase in the plasma concentrations of aluminium in all subjects after administration of the suspension, and in 14 of the subjects after administration of the tablet formulation, with C_max reached within the first 8 h in most subjects. Plasma levels were still elevated 72 h after dosing. The variability in plasma levels of aluminium was significantly higher after administration of the suspension (CV 39–53%) than after administration of the tablet (CV 29–44%), reflecting greater absorption of aluminium from the suspension formulation in three subjects. Similarly, the variance of the C_max, AUC_{(0–72 h)}, and AUC_(0–∞) (for both the raw data and the baseline adjusted data) were all higher for the suspension than for the tablet. A point estimate of the difference of the pharmacokinetic parameters (determined from the median of the arithmetic Walsh averages) indicated little or no difference in C_max, T_max, or AUC_(0–∞) in the two formulations. In summary, the performance of the suspension formulation of sucralphate is more variable than the tablet formulation in vivo and some patients may therefore have higher circulating levels of aluminium on therapy with the suspension formulation.     

左乙拉西坦缓释片的制备及其Beagle犬体内药动学研究

目的 制备左乙拉西坦缓释片,进行体外释放特性以及Beagle犬体内药动学研究。方法 按照筛选处方制备左乙拉西坦缓释片,以市售左乙拉西坦缓释片（Keppra-XR）为参比制剂,采用相似因子（f₂）法进行体外释放行为相似度评价;并将自制左乙拉西坦缓释片与市售普通片进行Beagle犬体内药动学参数比较。结果 自制左乙拉西坦缓释片与市售左乙拉西坦缓释片体外释放行为相似。市售左乙拉西坦普通片和自制左乙拉西坦缓释片的药动学参数T_max分别为（1.75±0.50）和（5.50±1.00）h,C_max分别为（30.33±2.00）和（17.29±3.56）mg·L^-1,AUC_0-t分别为（186.88±8.83）和（202.50±34.20）mg·L^-1·h。结论 自制的左乙拉西坦缓释片具有缓释效果。     

Formulation and Evaluation of Dextromethorphan Hydrobromide Sustained Release Tablets

Sustained release (SR) matrix tablets of dextromethorphan hydrobromide were prepared by wet granulation using hydroxypropyl methyl cellulose (HPMC-K-100 CR) as the hydrophilic rate controlling polymer. The effect of the concentration of the polymer and different fillers on the in vitro drug release rate was studied. The studies indicated that the drug release can be modulated by varying the concentration of the polymer and the fillers. A complete cross-over bioavailability study of the optimized formulation of the developed sustained tablets and marketed immediate release tablets was performed on six healthy male volunteers. The extent of absorption of drug from the SR tablets was significantly higher than that for the marketed dextromethorphan hydrobromide tablet because of lower elimination rate and longer half-life.