Food-dependent disintegration of immediate release fosamprenavir tablets: In vitro evaluation using magnetic resonance imaging and a dynamic gastrointestinal system

In the present study, we demonstrated the value of two advanced tools, the TNO gastric and small Intestinal Model (TIM-1) and magnetic resonance imaging (MRI), for the in vitro evaluation of food-dependent disintegration of immediate release fosamprenavir tablets. Upon introduction of a tablet with the nutritional drink Scandishake Mix® in the stomach compartment of TIM-1, simulating the fed state, disintegration and fosamprenavir dissolution were significantly postponed compared to the fasted state (lag time 80 ± 23 min). This resulted in a lag in the appearance of bioaccessible fosamprenavir (<5% during the first 2 h), even though the nutritional state did not significantly alter the cumulative bioaccessibility after 5 h. These results were in agreement with the previously observed postprandial delay in gastric fosamprenavir tablet disintegration and subsequent amprenavir absorption in healthy volunteers. Therefore, TIM-1 can be used in tablet development to identify food-induced disintegration issues causing unexpected clinical behavior. From a mechanistic perspective, we applied MRI to illustrate impaired water ingress in fosamprenavir tablets immersed in the nutritional drink compared to simulated gastric fluid. This effect may be attributed to both competition between nutritional components and the tablet for the available water (indicated by reduced rotational and translational diffusion) as well as the possible formation of a food-dependent precipitation layer on the HPMC-coated tablet.     

The delayed dissolution of paracetamol products in the canine fed stomach can be predicted in vitro but it does not affect the onset of plasma levels

Although it is generally believed that paracetamol can be used as a marker of gastric emptying, there have been reports in the literature that show delayed dissolution of immediate release paracetamol tablets using standard in vitro setups and food-simulating media, delayed disintegration of paracetamol products in the fed stomach, and no correlation of paracetamol absorption with gastric emptying in the fed state. In this study, we confirmed that dissolution of Panodil and Apotel tablets is delayed in food-simulating media regardless of the in vitro hydrodynamics and on a formulation dependent manner. Further, we assessed the usefulness of in vitro dissolution data in the prediction of delayed disintegration time in the fed stomach and we examined the importance of delayed gastric disintegration on the onset of plasma levels using the canine model. In vitro dissolution data in cow's milk reflected the delayed disintegration of Panodil tablets in the fed stomach. In vitro dissolution of Apotel tablets in milk was delayed less than of Panodil and the effect of dosing conditions on the in vivo disintegration was not apparent. However, for the products tested in this study, there was no correlation between intragastric disintegration and onset of plasma levels probably because gastric emptying in also delayed in the fed state.     

Parallel Monitoring of Plasma and Intraluminal Drug Concentrations in Man After Oral Administration of Fosamprenavir in the Fasted and Fed State

Purpose

The purpose of this study was to explore the feasibility of linking the pharmacokinetic profile of a drug with its gastrointestinal behavior by simultaneously monitoring plasma and intraluminal drug concentrations. Fosamprenavir, a phosphate ester prodrug of the poorly water-soluble HIV-inhibitor amprenavir, was selected as model compound.

Methods

A single tablet of fosamprenavir (Telzir®) was administered to 5 volunteers in the fasted and fed state (simulated by intake of a nutritional drink). Gastric and duodenal fluids were aspirated in function of time and characterized with respect to the concentration of (fos)amprenavir, inorganic phosphate and pH. In parallel, blood samples were collected and analyzed for amprenavir.

Results

The observed plasma concentration-time profiles suggested a food-induced delay in the absorption of amprenavir: in the fed state, mean t _max increased by more than 150 min compared to the fasted state. A similar delay was seen in the duodenal appearance of fosamprenavir (concentrations in mM-range) and, after dephosphorylation, amprenavir (concentrations below 160 μM). This observation could be related to the behavior of fosamprenavir in the stomach. In the fasted state, gastric dissolution of fosamprenavir started immediately, resulting in a C _max of 4?±?2 mM after 43?±?15 min; however, in the fed state, the fosamprenavir concentration remained below 20 μM for the first 90 min after drug intake. The postponed gastric dissolution may be attributed to a food-induced delay in tablet disintegration.

Conclusion

For the first time, the pharmacokinetic profile of a drug was monitored in parallel with its gastrointestinal concentrations. The observed food effect in the plasma concentration-time profile of amprenavir after intake of its phosphate ester prodrug could be related to a food-induced delay in gastric dissolution of fosamprenavir.     

In Vivo Evaluation of Enteric-Coated Naproxen Tablets Using Gamma Scintigraphy

Seven healthy, male volunteers were entered into a randomized, open crossover study of the gastrointestinal transit of two enteric-coated 500-mg naproxen tablets. Two radiolabeled tablets were given to each volunteer on two occasions separated by 7 days, once in the fasted state and once after breakfast. Radiolabeling of tablets was achieved by the incorporation of samarium-152 oxide during manufacture, followed by neutron activation of the tablet to produce the gamma-emitting isotope samarium-153. No loss of tablet integrity was seen in the stomach and all tablets disintegrated in the small intestine. Onset of tablet disintegration was controlled predominantly by gastric emptying. Time in the small intestine prior to tablet disintegration was independent of food intake. Naproxen blood levels with time were consistent with the delayed release of naproxen from the tablets. Overall, transit, disintegration, and absorption were as expected from an enteric-coated tablet.     

Evaluation of an enteric coated naproxen tablet using gamma scintigraphy and pH monitoring

Enteric coated naproxen tablets and pH-sensitive radiotelemetry capsules were both radiolabelled and administered to 6 healthy volunteers following breakfast. The median gastric emptying times for the tablets and capsules were 3.3 h and 4.2 h, respectively. In general, the intragastric pH remained below 2 with only transient increases following food consumption. Five of the naproxen tablets disintegrated in the small intestine and one in the stomach. In the ileum the pH was greater than 6 resulting in a mean time for tablet disintegration of 1.2 h after gastric emptying. There was a close correlation between tablet disintegration and the first detection of naproxen in the blood. Peak plasma concentrations of the drug occurred 4 h after tablet disintegration. This study has demonstrated that gastric emptying is the main factor influencing the onset of drug release from enteric coated tablets.     

An investigation of the disintegration of tablets in biorelevant media

The purpose of the study was to examine the disintegration of tablets in media designed to simulate conditions pertaining in the stomach. Although many studies have been performed to determine dissolution rates in these media, little work has been undertaken on the preliminary step in dissolution, namely disintegration.

Two tablet formulations were prepared. One disintegrated rapidly (under 25 s in water) and the other more slowly (8 min in water).

The disintegration times were measured by the BP 2000 test using discs. For the rapidly disintegrating tablets, disintegration times were similar in all media except for whole milk. This media is used to simulate the fed stomach and disintegration times were over five times longer than in the other media (P < 0.05). A similar effect was seen with the poorly disintegrating tablets in milk, and prolonged times were also observed in some of the other media. For these latter media, there was a good correlation between the penetration rate of the fluid into the tablet and the disintegration time. Penetration rates for milk were also slow which may be a reflection of its relatively high viscosity and low surface tension.     

Gastrointestinal transit of an enteric-coated delayed-release 5-aminosalicylic acid tablet

Gastrointestinal transit of an enteric-coated, delayed-release 5-aminosalicylic acid tablet radiolabelled with indium-111 has been monitored in a preliminary study with eight healthy subjects using gamma scintigraphy. Gastric emptying of the tablet was delayed by the presence of food in the stomach. Disintegration occurred about 5 hours after the tablet left the stomach. There was close agreement between the tablet disintegration times and the initial detection of drug in the blood. The site of disintegration could be established in most instances; approximately 80% of the doses resulted in drug dispersion within the ascending colon. The coated tablets provide an effective means of drug delivery to the proximal colon.     

Gamma-scintigraphic study of the gastrointestinal transit and in vivo dissolution of a controlled release diclofenac sodium formulation in xanthan gum matrices

A xanthan gum matrix controlled release tablet formulation containing diclofenac sodium was evaluated in vitro and was found to release the drug at a uniform rate. The gastrointestinal transit behaviour of the formulation as determined by gamma scintigraphy, using healthy male volunteers under fasted and fed conditions, indicated that gastric emptying was delayed with food intake. In contrast, the small intestinal transit remained practically unchanged under both food statuses. Therefore, the delay in caecal arrival observed in the fed state can be attributed to the delay in gastric emptying. Rate of diclofenac sodium absorption was generally higher in the fed state compared to the fasted state, however the total amount absorbed under both food statuses remained practically the same. The rate of in vivo dissolution of the drug in the fed state was faster compared to that in the fasted state. Thus, at the time of caecal arrival, in vivo dissolution was complete in the fed state, unlike in the fasted state, where almost 60% of the drug was delivered to the colon.     

Preparation and evaluation of press-coated aminophylline tablet using crystalline cellulose and polyethylene glycol in the outer shell for timed-release dosage forms

In an attempt to achieve chronopharmacotherapy for asthma, press-coated tablets (250 mg), which contained aminophylline in the core tablet in the form of low-substituted hydroxypropylcellulose (L-HPC) and coated with crystalline cellulose (PH-102) and polyethylene glycol (PEG) at various molecular weights and mixing ratios in the amounts of PH-102 and PEG as the outer shell (press-coating material), were prepared (chronopharmaceutics). Their applicability as timed-release (delayed-release) tablets with a lag time of disintegration and a subsequent rapid drug release phase was investigated. Various types of press-coated tablets were prepared using a tableting machine, and their aminophylline dissolution profiles were evaluated by the JP paddle method. Tablets with the timed-release characteristics could be prepared, and the lag time of disintegration was prolonged as the molecular weight and the amount of PEG, for example PEG 500,000, in the outer shell were increased. The lag time of disintegration could be controlled by the above-mentioned method, however, the pH of the medium had no effect on disintegration of the tablet and dissolution behavior of theophylline. The press-coated tablet (core tablet:aminophylline 50 mg, L-HPC and PEG 6000; outer shell:PH-102:PEG = 8:2 200 mg) with the timed-release characteristics was administered orally to rabbits for an in vivo test. Theophylline was first detected in plasma more than 2 h after administration; thus, this tablet showed a timed-release characteristics in the gastrointestinal tract. The time (tmax) required to reach the maximum plasma theophylline concentration (Cmax) observed after administration of the press-coated tablet was significantly (p < 0.05) delayed compared with that observed after administration of aminophylline solution in the control experiment. However, there was no difference in Cmax and area under the plasma theophylline concentration-time curve (AUC0-->24) between the press-coated tablet and aminophylline solution. These results suggest that the press-coated aminophylline tablet (with the timed-release characteristic) offers a promising forms of theophylline chronotherapy for asthma.     

Evaluation of food effect on the oral absorption of clarithromycin from immediate release tablet using physiological modelling

Background: Food may affect the oral absorption of drugs. Purpose: The aim of the present study was to investigate the influence of food on the oral absorption of clarithromycin by evaluating the effect of media parameters, such as pH, bile secretions and food composition, on the release of the drug from immediate release tablets, using in vitro and in silico assessments. Method: The solubility, disintegration and dissolution profiles of clarithromycin 500 mg immediate release tablets in compendial media with/without the addition of a homogenized FDA meal as well as in biorelevant simulated intestinal media mimicking fasting and fed conditions were determined. These in vitro data were input to GastroPlus?, which was used for developing a physiological absorption model capable of anticipating the effect of food on clarithromycin absorption. Level A in vitro–in vivo linear correlations were established using a mechanistic absorption modelling based deconvolution approach. Results: The pH of the media has a profound effect on clarithromycin solubility, tablet disintegration and drug release. Clarithromycin has lower solubility in biorelevant media compared with other media, due to complex formation with bile salts. Clarithromycin tablets exhibited prolonged disintegration times and reduced dissolution rates in the presence of the standard FDA meal. The simulation model predicted no significant food effect on the oral bioavailability of clarithromycin. The developed IVIVC model considered SIF, acetate buffer and FaSSIF media to be the most relevant from the physiological standpoint. Conclusion: The intake of a standard FDA meal may have no significant effect on the oral bioavailability of clarithromycin immediate release tablet.     

Stabilization Mechanism of Roxithromycin Tablets Under Gastric pH Conditions

Macrolide antibiotics are widely used at clinical sites. Clarithromycin (CAM), a 14-membered macrolide antibiotic, was reported to gelate under acidic conditions. Gelation allows oral administration of acid-sensitive CAM without enteric coating by hindering the penetration of gastric fluid into CAM tablets. However, it is unknown whether this phenomenon occurs in other macrolide antibiotics. In this study, we examined the gelation ability of 3 widely used macrolide antibiotics, roxithromycin (RXM), erythromycin A, and azithromycin. The results indicated that not only CAM but also RXM gelated under acidic conditions. Erythromycin A and azithromycin did not gelate under the same conditions. Gelation of RXM delayed the disintegration of the tablet and release of RXM from the tablet. Disintegration and release were also delayed in commercial RXM tablets containing disintegrants. This study showed that 2 of the 4 macrolides gelated, which affects tablet disintegration and dissolution and suggests that this phenomenon might also occur in other macrolides.     

The gastric emptying of food as measured by gamma-scintigraphy and electrical impedance tomography (EIT) and its influence on the gastric emptying of tablets of different dimensions

A study in human volunteers has been designed to evaluate the influence of different food regimes on the gastric emptying of 3 mm and 10 mm diameter tablets. Dextrose and beef drinks were used as liquid food; a mixture of minced beef and mashed potato (shepherd's pie) was used as a solid meal. The gastric emptying of these foods was monitored simultaneously with electrical impedance tomography (EIT) and gamma-scintigraphy (GS), and was quantified in terms of the time before gastric emptying started, the lag time, the mean gastric residence time (MGRT) and its variance (VGRT), and the time for complete emptying. The gastric emptying time of the tablets was established by monitoring the position of the tablets, which had been labelled with suitable radio isotopes, by GS. The two systems for monitoring gastric emptying of the foods did not provide equivalent results: times obtained with EIT were generally shorter than those obtained with GS for the liquid foods, but were longer for the solid meal. There was only a slight difference in the emptying times of the two liquid foods, whereas values for MGRT, VGRT and the time for complete emptying were considerably longer for the solid meal. In nearly all instances the tablets emptied after the foods had emptied completely from the stomach. Gastric emptying times were longer for the 3 mm tablets than the 10 mm tablets, whatever food they were taken with. The difference between the median emptying times was significant when the meal was either a dextrose solution or a beef drink, but not when the meal was shepherd's pie. The increase in gastric emptying time of tablets induced by solid food was greater than that associated with the differences in tablet size. By providing a protocol that did not allow the administration of further food until after the tablets had emptied from the stomach, no tablet emptying times exceeded 6 h.     

Understanding the in vivo performance of enteric coated tablets using an in vitro-in silico-in vivo approach: Case example diclofenac

Individual pharmacokinetics after administration of enteric coated tablets are often highly variable and this has been ascribed to the interaction of the dosage form with the physiology of the gastrointestinal tract. This research aimed to explore the influence of interactions between enteric coated tablets and physiological factors such as gastric and intestinal pH as well as gastric emptying on the release of drug from the dosage form and the subsequent plasma profile, using diclofenac as a case example.A physiologically based pharmacokinetic (PBPK) model for monolithic enteric coated dosage forms was designed and coupled with biorelevant dissolution results to predict PK profiles of diclofenac from Voltaren® tablets in both fasted and fed humans. The paddle method was used to obtain the dissolution profiles of diclofenac in biorelevant media. The Noyes–Whitney model was employed to describe the dissolution kinetics. The PBPK model was set up using STELLA® software. A single unit enteric coated tablet was assumed to be emptied from stomach only with the house-keeping wave. Timing of the emptying was simulated using a random number generator to statistically estimate gastric emptying times after ingestion. The lag times and the dissolution rate used as input parameters in the STELLA® model were adjusted according to the pre-exposure period. The oral PK profiles were predicted for each virtual subject individually, and then the mean profiles and standard deviations were calculated.The dissolution profiles were highly affected by the period of pre-exposure in FaSSGF. A long period of pre-exposure of the tablet prolonged the lag time and decreased the dissolution rate. The results of the pharmacokinetic simulations showed that not only the mean profiles in the fasted state but also the variability could be predicted successfully using data generated for the individual virtual subjects. The results emphasize the importance of accounting for the range of pH profiles and gastrointestinal transit in the target population when predicting plasma profiles of enteric coated dosage forms and point to problems in demonstrating bioequivalence for dosage forms of this type.     

Absorption of acetylsalicylic acid from enteric-coated tablets in relation to gastric emptying and in-vivo disintegration

The absorption of acetylsalicylic (ASA) acid from enteric coated tablets was studied in relation to gastric emptying and in-vivo disintegration. ASA tablets labelled with 51Cr were given to six healthy subjects under fasting and non-fasting conditions. The position and disintegration of the 51Cr-labelled tablets was followed by external radiation measurement and the amount of salicylic acid in blood and urine was analysed. The absorption of ASA from the studied enteric coated tablets was usually correlated with gastric emptying and in-vivo disintegration. However in some cases the absorption can be delayed between 10-20 h even if gastric emptying and disintegration of the tablet have occurred.     

In vitro and in vivo evaluation of a fast-disintegrating lyophilized dry emulsion tablet containing griseofulvin.

Development of a fast-disintegrating lyophilized dry emulsion (LDE) tablet that enhanced the in vitro dissolution and in vivo absorption of griseofulvin (GF) is presented. The LDE tablets were prepared by freeze-drying o/w emulsions of GF, a drug for which bioavailability is known to be enhanced by fat co-administration. Oil-in-water emulsions were prepared using a gelatin solution (2%, w/v) as the water phase and medium chain triglycerides (Miglyol) or sesame oil as the oil phase. In addition, different emulsifiers were evaluated. The influence of formulation parameters on the disintegration and in vitro dissolution of GF from LDE tablets along with other tablet characteristics were investigated. A significant influence of the emulsifier type on the tablet disintegration time was seen (p<0.01). Results obtained from dissolution studies showed that LDE tablets of GF improved the dissolution rate of the drug compared to the plain drug. The extent of absorption of GF from a selected LDE tablet formulation as compared to an immediate release conventional tablet as reference after single oral dose (125mg) administration was determined in four healthy subjects using a randomized crossover design. In this study, the rate of absorption of GF from LDE tablet was faster than that from the reference tablet and had significantly higher (p=0.02) peak plasma concentration (more than three times higher) and shortened time to C(max) by 4h (p=0.014). The extent of absorption expressed by AUC was 85% larger as compared to the commercial tablet. Stability results, after 6 months storage of LDE tablets at 25 degrees C and 60% relative humidity, showed a slight increase in disintegration time and residual moisture content, while results from dissolution studies showed slightly slower initial drug release.     

Process optimization for continuous extrusion wet granulation

Three granulating binders in high drug-load acetaminophen blends were evaluated using high shear granulation and extrusion granulation. A polymethacrylate binder enhanced tablet tensile strength with rapid disintegration in simulated gastric fluid, whereas polyvinylpyrrolidone and hydroxypropyl cellulose binders produced less desirable tablets. Using the polymethacrylate binder, the extrusion granulation process was studied regarding the effects of granulating liquid, injection rate and screw speed on granule properties. A full factorial experimental design was conducted to allow the statistical analysis of interactions between extrusion process parameters. Response variables considered in the study included extruder power consumption (screw loading), granule bulk/tapped density, particle size distribution, tablet hardness, friability, disintegration time and dissolution.     

Gastroscopic and pharmacokinetic evaluation of a new pivmecillinam tablet

Summary Three different pivmecillinam preparations, a conventional 200 mg tablet (P tablet) and two new formulations containing respectively pivmecillinam 200 mg and 400 mg plus Avicel^? (microcrystalline cellulose) as a disintegrator (PA tablet), were compared in vitro and in a gastroscopic study in 8 healthy volunteers. Disintegration of the PA tablet was significantly more rapid both in vitro and in the stomach. Following disintegration, the content of the PA tablet was spread over a larger area of the gastric mucosa (1088 mm²) than was observed with the P tablets (408 mm²). Three of the 8 volunteers taking the P tablet developed hyperaemia, interstitial bleeding or erosions of the mucosa of the stomach. No such reactions were seen with the PA tablets. Serum concentrations of mecillinam following ingestion of pivmecillinam tablets were determined in three groups of subjects; fasting volunteers, both supine and ambulant, and in ambulant subjects who took the preparation with a light meal. There was a tendency for the new PA tablets to produce a higher peak serum level as well as greater bioavailability of mecillinam. Administration of the PA tablets with a meal significantly increased the peak serum level and total bioavailability of the drug. On the basis of our observations we recommend adoption of the new PA tablet, because of its quick passage through the oesophagus and its more rapid and complete disintegration in the stomach.     

New oral solid dosage form for furosemide oral administration

Furosemide (FURO) is a drug labeled in class IV of the Biopharmaceutics Classification System (BCS) as it is both poor soluble and poor permeable. The aim of this work was to improve FURO biopharmaceutical properties by its formulation in a new solid oral dosage form. It consists in the realization of the composite MgAl-HTlc-FURO, obtained by FURO intercalation into the inorganic matrix hydrotalcite (MgAl-HTlc), and its successive formulation in tablets intended to be swallowed whole and to disintegrate rapidly in the stomach. These formulations were prepared by direct compression of a simple powder mixture constituted by MgAl-HTlc-FURO, a super disintegrant (Explotab, PolyplasdoneXL, PolyplasdoneXL-10, PolyplasdoneINF 10 or L-HPCLH-21) and a filler. The prepared formulations were submitted to disintegration time tests, and only those displaying the lowest disintegration time in gastric medium were submitted to in vitro release studies. Drug dissolution profiles from MgAl-HTlc-FURO tablets were compared with those containing crystalline FURO alone or physically mixed to MgAl-HTlc instead of MgAl-HTlc-FURO. The results revealed that tablets containing MgAl-HTlc-FURO give the best dissolution profile and that L-HPCLH-21 is able to promote the highest drug release in gastric medium, resulting in the most suitable super disintegrant in comparison with the other tested.     

葛根总黄酮生物粘附性缓释片体外组织粘附力及释放度研究

目的 :探讨葛根总黄酮缓释片的体外释放度及其释药动力学 ,测定、比较生物粘附性缓释片和普通片与家兔离体胃、小肠组织的粘附力。方法 :采用转篮法 ,以0 1mol/LHCl900ml为溶出介质 ,转速100r/min测定其累积释放度 ,并分别用单指数模型、威布尔分布函数、Higuchi方程、零级释放模型对释放度进行释药动力学模拟 ,根据各模型拟合的AIC计算值与实测值的绝对误差和相对误差确定缓释片的最佳拟合模型 ,同时以自制粘附力测定装置测定、比较生物粘附性缓释片及普通片与家兔离体胃、肠组织的粘附力。结果 :缓释片以单指数模型拟合最佳 ,生物粘附性缓释片与家兔离体胃、肠组织的粘附力明显大于普通片 (P<0 01) ,且与小肠的粘附力大于胃 (P<0 05)。结论 :缓释片在体外释药动力学符合单指数模型 ;生物粘附性缓释片在胃、肠道具有较强的粘附作用。     

魔芋葡甘露聚糖在灰黄霉素片制备中的应用

目的:探讨魔芋葡甘露聚糖在灰黄霉素片制备中的应用.方法:以魔芋葡甘露聚糖作为黏合剂,采用湿法制粒压片法制备灰黄霉素片,并进行质量检验.结果:所得灰黄霉素片的硬度、脆碎度、崩解时限、溶出速度及溶出度各项指标均有明显的改善,质量检查合格.结论:以魔芋葡甘露聚糖为黏合剂制备的灰黄霉素片崩解完全,溶出度增大.