Evaluation and Comparison of Physicomechanical Characteristics of Gelatin and Hypromellose Capsules

ABSTRACT

The aim of this study is evaluation and comparison of physical and mechanical properties of hypromellose and gelatin capsules. For this purpose, the empty and filled capsules of hypromellose and gelatin (size 4) were examined in regard with their physical and mechanical characteristics, employing textural analysis, and disintegration properties in various immersion fluids, utilizing a USP 28 disintegration apparatus. The results demonstrated that owing to their greater water permeability, gelatin capsules disintegrate much faster than hypromellose shells in all tested media. However, hypromellose capsules showed a more uniform pattern of dispersion in the disintegration fluids. As for mechanical properties, at ambient conditions, gelatin capsules appeared to be harder and stronger with less elasticity as compared with hypromellose shells. On the contrary, at an elevated temperature, gelatin capsules demonstrated lower resilience. This study shows that hypromellose capsules have excellent properties and are promising as far as regulatory, manufacturing, religious, and dietary issues are concerned.     

Evaluation and comparison of physicomechanical characteristics of gelatin and hypromellose capsules

The aim of this study is evaluation and comparison of physical and mechanical properties of hypromellose and gelatin capsules. For this purpose, the empty and filled capsules of hypromellose and gelatin (size 4) were examined in regard with their physical and mechanical characteristics, employing textural analysis, and disintegration properties in various immersion fluids, utilizing a USP 28 disintegration apparatus. The results demonstrated that owing to their greater water permeability, gelatin capsules disintegrate much faster than hypromellose shells in all tested media. However, hypromellose capsules showed a more uniform pattern of dispersion in the disintegration fluids. As for mechanical properties, at ambient conditions, gelatin capsules appeared to be harder and stronger with less elasticity as compared with hypromellose shells. On the contrary, at an elevated temperature, gelatin capsules demonstrated lower resilience. This study shows that hypromellose capsules have excellent properties and are promising as far as regulatory, manufacturing, religious, and dietary issues are concerned.     

Hard Gelatin and Hypromellose (HPMC) Capsules: Estimation of Rupture Time by Real-time Dissolution Spectroscopy

ABSTRACT

The objective of this study was to measure rupture time of gelatin and hypromellose (hydroxypropyl methylcellulose or HPMC) capsules using a novel approach based on real-time dissolution spectroscopy. Rupture time was measured in standard dissolution apparatus at a constant temperature using a dip-type fiber-optic probe. Labrasol released from the capsules was treated as the marker of the rupture process. Light scatter generated by the emulsified labrasol was detected by an ultrafast monochromator at scan rates approximating 24,000 nm/min. This technique was validated by measuring the dissolution time of gelatin capsules. Rupture times of hypromellose capsules were studied as a function of capsule size, capsule grade, and dissolution medium. Statistical correlations were analyzed by ANOVA. Rupture time of hypromellose capsules was dependent on both the medium and the grade of the capsule, and was independent of capsule size. The composition of the dissolution medium contributes to the rupture time of the capsules and should be considered when fast release and quick biological response is desired. Release delay, however, may not manifest itself in vivo and the time to maximum plasma concentration may not be significant.     

Hard gelatin and hypromellose (HPMC) capsules: estimation of rupture time by real-time dissolution spectroscopy

The objective of this study was to measure rupture time of gelatin and hypromellose (hydroxypropyl methylcellulose or HPMC) capsules using a novel approach based on real-time dissolution spectroscopy. Rupture time was measured in standard dissolution apparatus at a constant temperature using a dip-type fiber-optic probe. Labrasol released from the capsules was treated as the marker of the rupture process. Light scatter generated by the emulsified labrasol was detected by an ultrafast monochromator at scan rates approximating 24,000 nm/min. This technique was validated by measuring the dissolution time of gelatin capsules. Rupture times of hypromellose capsules were studied as a function of capsule size, capsule grade, and dissolution medium. Statistical correlations were analyzed by ANOVA. Rupture time of hypromellose capsules was dependent on both the medium and the grade of the capsule, and was independent of capsule size. The composition of the dissolution medium contributes to the rupture time of the capsules and should be considered when fast release and quick biological response is desired. Release delay, however, may not manifest itself in vivo and the time to maximum plasma concentration may not be significant.     

The In Vitro Dissolution of Theophylline from Different Types of Hard Shell Capsules

ABSTRACT

The in vitro dissolution of theophylline from two-piece hard shell capsules has been investigated using different types of capsule shells (gelatin, gelatin/polyethylene glycol, hydroxypropyl methylcellulose), different formulations, different capsule fill weights, and different tamping forces. Analysis of variance confirmed that the formulation and the capsule shell materials were the most important factors influencing drug dissolution. The maximum extent of drug dissolution was significantly increased when hydroxypropyl methylcellulose (HPMC) capsules were used. The mean dissolution time (MDT) was significantly reduced, indicating a faster dissolution rate of the drug from HPMC capsules. The addition of microfine cellulose to the formulations as filler reduced the MDT in all cases, whereas the addition of lactose monohydrate did not enhance drug dissolution. The study confirmed that a change from gelatin hard shell capsules to gelatin/PEG or HPMC hard shell capsules should not pose problems with respect to drug absorption or bioavailability.     

The in vitro dissolution of theophylline from different types of hard shell capsules

The in vitro dissolution of theophylline from two-piece hard shell capsules has been investigated using different types of capsule shells (gelatin, gelatin/polyethylene glycol, hydroxypropyl methylcellulose), different formulations, different capsule fill weights, and different tamping forces. Analysis of variance confirmed that the formulation and the capsule shell materials were the most important factors influencing drug dissolution. The maximum extent of drug dissolution was significantly increased when hydroxypropyl methylcellulose (HPMC) capsules were used. The mean dissolution time (MDT) was significantly reduced, indicating a faster dissolution rate of the drug from HPMC capsules. The addition of microfine cellulose to the formulations as filler reduced the MDT in all cases, whereas the addition of lactose monohydrate did not enhance drug dissolution. The study confirmed that a change from gelatin hard shell capsules to gelatin/PEG or HPMC hard shell capsules should not pose problems with respect to drug absorption or bioavailability.     

Time domain 1H NMR as a new method to monitor softening of gelatin and HPMC capsule shells

Defined mechanical properties are an essential requirement for any pharmaceutical dosage form and this is particularly important in the case of liquid-filled capsules. Changes in the mechanical properties may be induced by exposure of the capsules to humidity or by a shift of the water equilibrium that typically occurs when hydrophilic or amphiphilic fill masses are used, for example, in self-emulsifying drug delivery systems. This study aims to characterize the softening of empty hard gelatin and hydroxypropyl methylcellulose (HPMC) capsules by means of mechanical tests, a Bareiss hardness test, and a stiffness test using a texture analysis method. A benchtop time domain NMR method is applied in addition to characterize the physico-chemical state of water in the capsule shells and to correlate this with the results of the mechanical tests. Hardness and stiffness measurements resulted in corresponding values, showing a softening for both capsule materials in a humid environment, which was most pronounced beyond 60% relative humidity. The capsules made of gelatin exhibited in general higher stiffness and hardness values compared to the HPMC capsules. The physico-chemical state of water in the capsule shells, as probed by a time domain NMR method, was interpreted in terms of a population balance model. Three different water populations were identified that differ in their molecular mobility, as indicated by their characteristic spin-lattice relaxation times, T1. The most loosely bound water fraction dominated in the capsule shells in the range beyond 60% relative humidity. Numerical correlation of the data led to a heuristic equation between the NMR-derived fraction of loosely bound water in the capsule shells and their mechanical stiffness and hardness. Adequate models were obtained for both capsule types, gelatin, and HPMC. Mechanical measurements of pharmaceutical capsules are generally destructive and time consuming. Testing is usually performed in an analytical laboratory, off-line from the manufacturing process, and involves only a small number of samples. Based on the here presented correlation between mechanical stiffness measurements and benchtop time domain NMR data, the latter method may be used as a nondestructive alternative for mechanical testing. This study also opens the possibility to investigate liquid-filled capsules and to establish a process analytical technology (PAT) during manufacturing.     

Time Domain 1H NMR as a New Method to Monitor Softening of Gelatin and HPMC Capsule Shells

ABSTRACT

Defined mechanical properties are an essential requirement for any pharmaceutical dosage form and this is particularly important in the case of liquid-filled capsules. Changes in the mechanical properties may be induced by exposure of the capsules to humidity or by a shift of the water equilibrium that typically occurs when hydrophilic or amphiphilic fill masses are used, for example, in self-emulsifying drug delivery systems. This study aims to characterize the softening of empty hard gelatin and hydroxypropyl methylcellulose (HPMC) capsules by means of mechanical tests, a Bareiss hardness test, and a stiffness test using a texture analysis method. A benchtop time domain NMR method is applied in addition to characterize the physico-chemical state of water in the capsule shells and to correlate this with the results of the mechanical tests. Hardness and stiffness measurements resulted in corresponding values, showing a softening for both capsule materials in a humid environment, which was most pronounced beyond 60% relative humidity. The capsules made of gelatin exhibited in general higher stiffness and hardness values compared to the HPMC capsules. The physico-chemical state of water in the capsule shells, as probed by a time domain NMR method, was interpreted in terms of a population balance model. Three different water populations were identified that differ in their molecular mobility, as indicated by their characteristic spin-lattice relaxation times, T1. The most loosely bound water fraction dominated in the capsule shells in the range beyond 60% relative humidity. Numerical correlation of the data led to a heuristic equation between the NMR-derived fraction of loosely bound water in the capsule shells and their mechanical stiffness and hardness. Adequate models were obtained for both capsule types, gelatin, and HPMC. Mechanical measurements of pharmaceutical capsules are generally destructive and time consuming. Testing is usually performed in an analytical laboratory, off-line from the manufacturing process, and involves only a small number of samples. Based on the here presented correlation between mechanical stiffness measurements and benchtop time domain NMR data, the latter method may be used as a nondestructive alternative for mechanical testing. This study also opens the possibility to investigate liquid-filled capsules and to establish a process analytical technology (PAT) during manufacturing.     

Imprinting on empty hard gelatin capsule shells containing titanium dioxide by application of the UV laser printing technique

The purpose of this study was to examine the application of ultraviolet (UV) laser irradiation to printing hard gelatin capsule shells containing titanium dioxide (TiO₂) and to clarify how the color strength of the printing by the laser could be controlled by the power of the irradiated laser. Hard gelatin capsule shells containing 3.5% TiO₂ were used in this study. The capsules were irradiated with pulsed UV laser at a wavelength of 355?nm. The color strength of the printed capsule was determined by a spectrophotometer as total color difference (dE). The capsules could be printed gray by the UV laser. The formation of many black particles which were agglomerates of oxygen-defected TiO₂ was associated with the printing. In the relationship between laser peak power of a pulse and dE, there were two inflection points. The lower point was the minimal laser peak power to form the black particles and was constant regardless of the dosage forms, for example film-coated tablets, soft gelatin capsules and hard gelatin capsules. The upper point was the minimal laser peak power to form micro-bubbles in the shells and was variable with the formulation. From the lower point to the upper point, the capsules were printed gray and the dE of the printing increased linearly with the laser peak power. Hard gelatin capsule shells containing TiO₂ could be printed gray using the UV laser printing technique. The color strength of the printing could be controlled by regulating the laser energy between the two inflection points.     

Dissolution Characteristics of Capsule Shells and Drug Release from Commercial Tetracycline-Hcl Capsules

Abstract

The dissolution characteristics of the gelatin shells of four brands of tetracycline-HCl capsules were examined by measuring the shell rupture time (t_r) in a modified version of two-blade stirrer apparatus under various stirrer depth, ionic strength, and pH conditions. The dissolution rate of tetracycline-HCl from these capsules was also determined using the U.S.P. XIX dissolution apparatus. While no significant effect of stirrer depth on t_r was found, increasing the basket-stirrer distance from the bottom of the flask from 0.2 to 2 cm was found to increase the dissolution rate of tetracycline-HCl from capsules significantly (p < 0.001). As the ionic strength was increased, the dissolution rates of both gelatin shell and tetracycline-HCl content were increased, however, increasing the ionic strength from 0.6 to 1.5 failed to produce any further increase in t_r. The pH of the dissolution fluid significantly (p < 0.01) influenced the dissolution rate of the capsule shell and t_r was longest at pH = 4. A linear, inverse relationship between pH and tetracycline-HCl dissolution rate constant (k_s) was obtained. While a good correlation between t_r and k_s was obtained under certain conditions, capsule shell and tetracycline-HCl content showed different dissolution behaviour under other conditions. It is expected therefore, that under the latter conditions capsule shells had their maximum effect on drug release from the capsules studied.     

Development of self-microemulsifying drug delivery system for oral delivery of poorly water-soluble nutraceuticals

The objective of the study was to develop a self-microemulsifying drug delivery system (SMEDDS), also known as microemulsion preconcentrate, for oral delivery of five poorly water-soluble nutraceuticals or bioactive agents, namely, vitamin A, vitamin K2, coenzyme Q₁₀, quercetin and trans-resveratrol. The SMEDDS contained a 1:1 mixture (w/w) of Capmul MCM NF (a medium chain monoglyceride) and Captex 355 EP/NF (a medium chain triglyceride) as the hydrophobic lipid and Tween 80 (polysorbate 80) as the hydrophilic surfactant. The lipid and surfactant were mixed at 50:50 w/w ratio. All three of the SMEDDS components have GRAS or safe food additive status. The solubility of nutraceuticals was determined in Capmul MCM, Captex 355, Tween 80, and the SMEDDS (microemulsion preconcentrate mixture). The solubility values of vitamin A palmitate, vitamin K2, coenzyme Q₁₀, quercetin, and trans-resveratrol per g of SMEDDS were, respectively, 500, 12, 8, 56, and 87?mg. Appropriate formulations of nutraceuticals were prepared and filled into hard gelatin capsules. They were then subjected to in vitro dispersion testing using 250?mL of 0.01 N HCl in USP dissolution apparatus II. The dispersion test showed that all SMEDDS containing nutraceuticals dispersed spontaneously to form microemulsions after disintegration of capsule shells with globule size in the range of 25 to 200?nm. From all formulations, except that of vitamin K2, >80–90% nutraceuticals dispersed in 5–10?min and there was no precipitation of compounds during the test period of 120?min. Some variation in dispersion of vitamin K2 was observed due to the nature of the material used (vitamin K2 pre-adsorbed onto calcium phosphate). The present report provides a simple and organic cosolvent-free lipid-based SMEDDS for the oral delivery of poorly water-soluble nutraceuticals. Although a 50:50 w/w mixture of lipid to surfactant was used, the lipid content may be increased to 70:30 without compromising the formation of microemulsion.     

Influence of Enzymes and Surfactants on the Disintegration Behavior of Cross-Linked Hard Gelatin Capsules During Dissolution

ABSTRACT

Gelatin exhibits cross-linking upon storage at stress conditions. Capsules stored at these conditions fail to show appropriate in vitro dissolution. The aim of this study is to show the effect of surfactants in the medium on the disintegration of the gelatin capsule. This is demonstrated in the presence and absence of the enzymes pancreatin and pepsin, the function of which is to improve the dissolution. Sodium lauryl sulfate (SLS) and Tween 80 are tested as surfactants. When SLS is used in the medium, dissolution is significantly hampered due to the formation of a less soluble precipitate of gelatin. Compared to SLS, Tween 80 shows far better disintegration and solubility results in dissolution media with neutral or low pH. Therefore, it is concluded in this study that Tween 80 is preferred when a surfactant is necessary to comply with sink condition requirements.     

Influence of enzymes and surfactants on the disintegration behavior of cross-linked hard gelatin capsules during dissolution

Gelatin exhibits cross-linking upon storage at stress conditions. Capsules stored at these conditions fail to show appropriate in vitro dissolution. The aim of this study is to show the effect of surfactants in the medium on the disintegration of the gelatin capsule. This is demonstrated in the presence and absence of the enzymes pancreatin and pepsin, the function of which is to improve the dissolution. Sodium lauryl sulfate (SLS) and Tween 80 are tested as surfactants. When SLS is used in the medium, dissolution is significantly hampered due to the formation of a less soluble precipitate of gelatin. Compared to SLS, Tween 80 shows far better disintegration and solubility results in dissolution media with neutral or low pH. Therefore, it is concluded in this study that Tween 80 is preferred when a surfactant is necessary to comply with sink condition requirements.     

Semisolid matrix filled capsules: an approach to improve dissolution stability of phenytoin sodium formulation

Seven semisolid fill bases were selected for the formulation of 24 capsule formulations, each containing 100 mg of phenytoin sodium. The fill materials were selected based on the water absorption capacity of their mixtures with phenytoin sodium. The fill matrices included lipophilic bases (castor oil, soya oil, and Gelucire (G) 33/01), amphiphilic bases (G 44/14 and Suppocire BP), and water-soluble bases (PEG 4000 and PEG 6000). The drug:base ratio was 1:2. Excipients such as lecithin, docusate sodium, and poloxamer 188 were added to some formulations. The dissolution rate study indicated that formulations containing lipophilic and amphiphilic bases showed the best release profiles. These are F4 (castor oil-1% docusate sodium); F10 (castor oil-3% poloxamer 188); F14 (G33/01-10% lecithin); F17 (G33/01-1% docusate sodium), and F20 (Suppocire BP). Further, the dissolution stability of the five formulations above was assessed by an accelerated stability study at 30°C and 75% RH using standard Epanutin capsules for comparison. The study included the test and standard capsules either packed in the container of marketed Epanutin capsules (packed) or removed from their outer pack (unpacked). Release data indicated superior release rates of castor oil based formulations (F4 and F10) relative to standard capsules in both the unpacked and packed forms. For instance, the extent of drug release at 30 min after 1 month was 91% for F4 and F10 and 20% for standard capsules. Drug release from packed capsules after 6 months storage was 88% for both formulations F4 and F10 and 35% for standard capsules. In conclusion, the pharmaceutical quality of phenytoin sodium capsules can be improved by using a semisolid lipophilic matrix filled in hard gelatin capsules.     

Effect of Glycine/Citric Acid on the Dissolution Stability of Hard Gelatin Capsules

Abstract

Gelatin capsule crosslinking is a well-known phenomenon that results in reduced dissolution of capsule products with the passage of time and/or under accelerated stability conditions. These studies describe one means of preventing capsule crosslinking by incorporating glycine and citric acid into a triamterene/hydrochlorothiazide 37.5/25 mg capsule formulation (triam/HCTZ). Triam/HCTZ without glycine and citric acid showed extensive capsule crosslinking and then failed the USP dissolution specification after a 4-week accelerated (40°C/85% relative humidity [RH]) stability study. Triam/HCTZ containing glycine alone showed some improvement in the dissolution stability but did not prevent gelatin crosslinking. This formulation also failed dissolution specifications after a 4-week accelerated stability study. The same results were obtained when only citric acid was incorporated into the triam/HCTZ. However when glycine and citric acid were incorporated together into the triam/HCTZ, crosslinking was completely prevented. Dissolution profiles remained the same throughout 12-week accelerated stability studies, with little or no drop in the dissolution values throughout the test period. The above results were confirmed with follow-up studies using gemfibrozil and piroxicam as model drugs. Disintegration times for gemfibrozil and piroxicam capsule formulations without glycine and citric acid increased dramatically with observed pellicle formation, but there was little or no change in the disintegration time of the model drugs formulated with glycine and citric acid. The results of these studies demonstrated that when glycine and citric acid are present in some gelatin capsule formulations, pellicle formation or crosslinking of the capsule gelatin is prevented.     

The Influence of Disintegrant Level and Capsule Size on Dissolution of Hard Gelatin Capsules Stored in High Humidity Conditions

Abstract

Six batches of hard gelatin capsules were manufactured to explore the effect of disintegrant level and capsule fill porosity on the dissolution behavior of encapsulated dosage forms after exposure to high humidity. Size 0 capsules filled with powder blends containing 10 and 25% disintegrant dissolved faster than size 2 capsules filled with identical powder blends after storage under direct high humidity exposure. Interestingly, the trend was reversed when these identical products were exposed to high humidity but stored in, and protected by, a high density bottle-polypropylene container/closure system. It is hypothesized that capsules filled with a highly compacted powder blend, which are directly exposed to high humidity form a water layer at the gelatin-powder blend interface that inactivates the disintegrant.     

The Influence of Disintegrant Level and Capsule Size on Dissolution of Hard Gelatin Capsules Stored in High Humidity Conditions

Six batches of hard gelatin capsules were manufactured to explore the effect of disintegrant level and capsule fill porosity on the dissolution behavior of encapsulated dosage forms after exposure to high humidity. Size 0 capsules filled with powder blends containing 10 and 25% disintegrant dissolved faster than size 2 capsules filled with identical powder blends after storage under direct high humidity exposure. Interestingly, the trend was reversed when these identical products were exposed to high humidity but stored in, and protected by, a high density bottle-polypropylene container/closure system. It is hypothesized that capsules filled with a highly compacted powder blend, which are directly exposed to high humidity form a water layer at the gelatin-powder blend interface that inactivates the disintegrant.     

Generic omeprazole delayed-release capsules: in vitro performance evaluations

Background: After the patent on omeprazole delayed-release capsules expired, Food and Drug Administration (FDA) approved several generic omeprazole delayed-release capsule applications. FDA has received some complaints concerning a lack of therapeutic effect of the generic omeprazole delayed-release capsules. Aim: To investigate the quality of five different marketed generic omeprazole delayed-release capsules. Method: The dissolution characteristics of these generic omeprazole delayed-release capsules were determined according to the United States Pharmacopeia (USP). Additional dissolution studies under simulated in vivo physiological conditions were also conducted to determine whether generic omeprazole capsules would perform similarly under these conditions. Results: The experimental data show that all the generic omeprazole delayed-release capsules met the USP standards. The in vitro dissolution of generic drugs is similar to that of the brand omeprazole product. Conclusions: There is no scientific evidence to support the claims that the generic omeprazole delayed-release capsules perform differently from the brand omeprazole product in vitro.     

Erosion characteristics of an erodible tablet incorporated in a time-delayed capsule device

A time-delayed oral drug delivery device was investigated in which an erodible tablet (ET), sealing the mouth of an insoluble capsule, controlled the lag-time prior to drug release. The time-delayed capsule (TDC) lag-time may be altered by manipulation of the excipients used in the preparation of the ET. Erosion rates and drug release profiles from TDCs were investigated with four different excipient admixtures with lactose: calcium sulphate dihydrate (CSD), dicalcium phosphate (DCP), hydroxypropylmethyl cellulose (HPMC; Methocel® K100LV grade) and silicified microcrystalline cellulose (SMCC; Prosolv® 90 grade). Additionally, the compressibility of different insoluble coated capsules was tested at different moisture levels to determine their overall integrity and suitability for oral delivery. Erosion rates of CSD, DCP, and SMCC displayed a nonlinear relationship to their concentration, while HPMC indicated rapid first-order erosion followed by zero-order erosion, the onset of which was dependent on the HPMC concentration. Capsule integrity was confirmed to be most suitable for oral delivery when the insoluble ethyl cellulose coat was applied to a hard gelatin capsule using an organic spray coating process. T_50% drug release times varied between 245 (± 33.4) and 393 (± 40.8) minutes for 8% and 20% DCP, respectively, T_50% release times of 91 (± 22.1) and 167 (± 34.6) were observed for 8% and 20% CSD; both formulations showed incidence of premature drug release. The SMCC formulations showed high variability due to lamination effects. The HPMC formulations had T_50% release times of 69 (± 13.9), 213 (± 25.4), and 325 (± 30.3) minutes for 15%, 24%, and 30% HPMC concentrations respectively, with no premature drug release. In conclusion, HPMC showed the highest reproducibility for a range of time-delayed drug release from the assembled capsule formulation. The method of capsule coating was confirmed to be important by investigation of the overall capsule integrity at elevated humidity levels. The erosion characteristics of ETs containing HPMC may be described by gravimetric loss. The novel time-delayed capsule device presented in this study may be assembled to include an erodible tablet with a known concentration of HPMC. A variety of suitable drugs for targeted chronopharmaceutical therapy can beincorporated into such a device, ultimately improving drug efficacy and patient compliance, and reducing harmful side effects.     

Liquid Filled and Sealed Hard Gelatin Capsules

A method for sealing liquid filled hard gelatin capsules has been protection against oxidation, have very effective barrier/properties against bad smelling products and have short disintegration times. These properties demonstrate that the liquid filled and sealed hard gelatin capsule offers a real alternative to the soft gelatin capsule.