Paddle Method Research Articles

Development of Polyvinyl Alcohol/Polyethylene Glycol Copolymer-based Orodispersible Films Loaded with Entecavir: Formulation and In vitro Characterization.

The aim of the study is to prepare entecavir (ETV)-loaded orodispersible films (ODFs) using polyvinyl alcohol (PVA)/polyethylene glycol (PEG) graft copolymer (Kollicoat® IR) as a film-forming agent, and further to evaluate the dissolution rate, mechanical and physicochemical properties of films. ETV-ODFs were prepared by a solvent casting method. The amount of film-forming agent, plasticizer, and disintegrating agent was optimized in terms of the appearance, thickness, disintegration time and mechanical properties of ODFs. The compatibility between the drug and each excipient was conducted under high temperature (60 °C), high humidity (RH 92.5%), and strong light (4500 Lx) for 10 days. The dissolution study of optimal ODFs compared with the original commercial tablet (Baraclude®) was performed using a paddle method in pH 1.0, pH 4.5, pH 6.8, and pH 7.4 media at 37 °C. The morphology of ODFs was observed via scanning electron microscopy (SEM). The mechanical properties such as tensile strength (TS), elastic modulus (EM), and percentage elongation (E%) of ODFs were evaluated using the universal testing machine. The physicochemical properties of ODFs were investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR). The related substances were less than 0.5% under high temperature, high humidity, and strong light for 10 days when ETV was mixed with excipients. The optimal formulation of ODFs was set as the quality ratio of Kollicoat® IR, glycerol, sodium alginate (ALG-Na): TiO2: MCC+CMC-Na: ETV was 60:9:12:1:1:1. The drug-loaded ODFs were white and translucent with excellent stripping property. The thickness, disintegration time, EM, TS, and E% were 103.33±7.02 μm, 25.31±1.95 s, 25.34±8.69 Mpa, 2.14±0.26 Mpa, and 65.45±19.41 %, respectively. The cumulative drug release from ODFs was more than 90% in four different media at 10 min. The SEM showed that the drug was highly dispersible in ODFs, and the XRD, DSC, and FT-IR results showed that there occurred some interactions between the drug and excipients. In conclusion, the developed ETV-loaded ODFs showed relatively short disintegration time, rapid drug dissolution, and excellent mechanical properties. This might be an alternative to conventional ETV Tablets for the treatment of chronic hepatitis B.

Pharmaceutical Equivalence of Film-Coated and Chewable Tablets: A Comparative Dissolution Study Using Pulverized Chewable Tablets.

Famotidine is a histamine H2 receptor antagonist used in the treatment of gastrointestinal disorders. It is available in multiple formulations, including film-coated tablets, chewable tablets, oral suspension, and injections. The purpose of this study was to develop and evaluate the film-coated tablet (FT) containing famotidine, magnesium hydroxide, and precipitated calcium carbonate, designed to be pharmaceutically equivalent to the marketed chewable tablet (CT). To achieve the pharmaceutical equivalence of two tablets, the dissolution profiles of FT should be similar to those of CT. However, since CT is intended to be chewed before swallowing, testing it in its intact form would not provide accurate results. Therefore, pulverized chewable tablets (PCT) were used as the reference product. The dissolution, performed by the paddle method at 50 rpm, was analyzed by the validated UV method. Similarity factor (f2) and difference factor (f1) were calculated to assess the equivalence of the dissolution profiles. The results demonstrated that the dissolution profiles of the FT and CT were similar. Additionally, the acid-neutralizing capacity test confirmed the equivalence of the two antacids. This study is one of the first to propose that dissolution tests for pharmaceutical equivalence should be conducted on pulverized CTs when developing generic equivalents to CTs.

Establishment of Dissolution Test Method for Multi-Components in Traditional Chinese Medicine Preparations Based on In Vitro-In Vivo Correlation.

In this study, a multi-component integrated dissolution evaluation system of Yuanhu Zhitong tablets (YZTs) was established based on in vitro and in vivo correlation (IVIVC). The dissolution tests of five quality markers (Q-markers), including tetrahydropalmatine, α-allocryptopine, protopine, corydaline, and byakangelicin, in YZTs were conducted under different dissolution conditions, and pharmacokinetic studies were performed in beagle dogs to construct a correlation model using numerical deconvolution. The data of the five ingredients were integrated in vitro and in vivo according to the biopharmaceutical classification system (BCS) to establish an IVIVC integrating multiple Q-markers. The dissolution media with the best correlation of components were obtained and validated. The results showed that all five components were classified as BCS I compounds, and α-allocryptopine, byakangelicin, tetrahydropalmatine, and corydaline showed good correlation in the paddle method, 75 rpm, with dissolution media of artificial gastric fluid, acetate buffer, acetate buffer and 0.1 M HCl, respectively. Protopine showed good correlation in the paddle method, 100 rpm, with dissolution media of 0.1 M HCl. The integrated BCS I Q-markers showed the best correlation in the medium of acetate buffer. The multi-component integrated dissolution evaluation system established in this experiment accurately predicted the pharmacokinetic data of YZTs by verifying the media, which can be used for the quality control of YZTs. The present study provides an effective and promising strategy for the dissolution evaluation for traditional Chinese medicine preparations.

Development of 3D-printed dual-release fixed-dose combination through double-melt extrusion

This study aimed to develop a 3D-printed fixed-dose combination tablet featuring differential release of two drugs using double-melt extrusion (DME). The hot-melt extrusion (HME) process was divided into two steps to manufacture a single filament containing the two drugs. In Step I, a sustained-release matrix of acetaminophen (AAP) was obtained through HME at 190 °C using Eudragit® S100, a pH-dependent polymer with a high glass transition temperature. In Step II, a filament containing both sustained-release AAP from Step I and solubilized ibuprofen (IBF) was fabricated via HME at 110 °C using a mixture of hydroxy propyl cellulose (HPC-LF) and Eudragit® EPO, whose glass transition temperatures make them suitable for use in a 3D printer. A filament manufactured using DME was used to produce a cylindrical 3D-printed fixed-dose combination tablet with a diameter and height of 9 mm. To evaluate the release characteristics of the manufactured filament and 3D-printed tablet, dissolution tests were conducted for 10 h under simulated gastrointestinal tract conditions using the pH jump method with the United States Pharmacopeia apparatus II paddle method at 37 ± 0.5 °C and 50 rpm. Dissolution tests confirmed that both the sustained-release and solubilized forms of AAP and IBF within the filament and 3D-printed tablet exhibited distinct drug-release behaviors. The physicochemical properties of the filament and 3D-printed tablet were confirmed by thermogravimetric analysis, differential scanning calorimetry, powder X-ray diffraction, and Fourier-transform infrared spectroscopy. HME transforms crystalline drugs into amorphous forms, demonstrating their physicochemical stability. Scanning electron microscopy and confocal laser scanning microscopy indicated the presence of sustained AAP granules within the filament, confirming that the drugs were independently separated within the filament and 3D-printed tablets. Finally, sustained-release AAP and solubilized IBF were independently incorporated into the filaments using DME technology. Therefore, a dual-release 3D-printed fixed-dose combination was prepared using the proposed filament.

Commentary on "The Effect of Sampling Cannula on In Vitro Dissolution Testing with USP Paddle Method".

Commentary on "The Effect of Sampling Cannula on In Vitro Dissolution Testing with USP Paddle Method".

Development and validation of a UV spectrophotometric method for biowaiver studies in pyrazinamide tablets

Development and validation of a UV spectrophotometric method for biowaiver studies in pyrazinamide tablets

Preparation of tofacitinib sustained-release tablets using hot melt extrusion technology

This study aimed to develop a tablet that shows a drug release profile similar to the tofacitinib sustained-release tablet (Xeljanz XR®; OROS™) using hot melt extrusion technology. Tofacitinib citrate was selected as the drug. HPMCAS, HPMCP, and Kollidon VA64 were used as thermoplastic polymers to prepare a hot-melt extrudate. The extrudate was obtained from a twin screw extruder and pelletizer. The granules were compressed using a single punch press machine and then coated. TGA, DSC, XRD, FT-IR, and SEM were performed on the hot melt extrudate to understand its physicochemical properties. Dissolution tests were performed using the paddle method (USP Apparatus II). The results showed that the crystallinity state of tofacitinib changed to amorphous after the hot melt extrusion process; however, no chemical change was observed. The drug release profile was similar to that of Xeljanz XR®, which has an initial lag time owing to its OROS™ formulation; a coating process was performed to obtain a similar drug release profile. The lag time was controlled by adjusting the thickness of the coating layer. Moreover, the extrudate size and compression force during tableting did not significantly affect drug release. In conclusion, the new tofacitinib sustained-release tablet prepared using hot melt extrusion showed a drug release behavior similar to that of Xeljanz XR®.

Comparison of In vitro Dissolution Tests of five brands of Diclofenac Sodium delayed release tablets in Moroccan market

This study aims to evaluate the similarity of in-vitro dissolution profiles, of commercially available generics of diclofenac sodium delayed-release tablets, of 25mg strength, with the innovator brand in Moroccan Market. Dissolution profiles for five brands were determined using the paddle method from the United States Pharmacopoeia. For the aptitude verification of the method, in our experimental conditions, linearity and accuracy tests were performed. The rate of dissolution was determined by Ultra-Violet Spectroscopy at 276nm. The assessment between the generics and the brand medicine was carried out under the similarity factor approach. We also presented an overview of the dissolution principles of tablet dosage form, and the pharmacopoeia dissolution test recommendations in our case. To compliance with US pharmacopoeia specifications, the rate of dissolution should be not more than 10% after 2hours in the acid stage, and not less than 75% at 45 minutes in the buffer stage. Furthermore, two dissolution profiles are considered similar when the f2 value is ≥50. According to routine quality control, evaluating the rate dissolution at the final point, all the generic medicines marketed in Morocco, meet the specification of the dissolution testing. However, using the comparison of dissolution profiles, only generic-2 is interchangeable with the innovator brand.

Evaluation of single granule release characteristics of controlled release granules with porous ethylcellulose membrane

A basic dissolution study of single granule in a controlled-release capsule formulations was conducted. Controlled-release granules were prepared using porous Ethylcellulose membranes, and single granule dissolution profiles was compared with those of the Japanese pharmacopoeia (JP) paddle method. Dissolution profile from one granule was found to be dependent on the solubility of the drug.

Bicarbonate buffer dissolution test with gentle mechanistic stress for bioequivalence prediction of enteric-coated pellet formulations

This study aimed to develop a dissolution test that can predict the bioequivalence (BE) of enteric-coated pellet formulations. The original duloxetine hydrochloride capsule (reference formulation (RF); Cymbalta® 30 mg capsule) and four generic test formulations (two capsules (CP) and two orally disintegrating tablets (OD)) were used as model formulations. Clinical BE studies were conducted on 24–47 healthy male subjects under fasting conditions. Dissolution tests were performed using a compendial paddle method (PD) (paddle speed: 50 rpm) and a flow-through cell method (FTC) (flow rate: 4 mL/min). For a further test, cotton balls were added to the vessel to apply gentle mechanistic stress to the formulations, and paddle speed was reduced to 10 rpm (paddle with cotton ball method (PDCB)).All the dissolution tests were conducted with 0.01 M HCl (pH 2.0) for 0.5 h followed by 10 mM bicarbonate buffer solutions (pH 6.5) for 4 h. One each of the two CP and two OD showed BE with RF. PDCB was able to discriminate between BE and non-BE formulations, while this was not possible with PD and FTC. In PDCB, the cotton balls intermittently moved the pellets near the vessel bottom. PDCB is useful for predicting BE during formulation development.

Revisiting Supersaturation of a Biopharmaceutical Classification System IIB Drug: Evaluation via a Multi-Cup Dissolution Approach and Molecular Dynamic Simulation.

As a subclass of the biopharmaceutical classification system (BCS) class II, basic drugs (BCS IIB) exhibit pH-dependent solubility and tend to generate supersaturation in the gastrointestinal tract, leading to less qualified in vitro-in vivo correlation (IVIVC). This study aims to develop a physiologically based multi-cup dissolution approach to improve the evaluation of the supersaturation for a higher quality of IVIVC and preliminarily explores the molecular mechanism of supersaturation and precipitation of ketoconazole affected by Polyvinylpyrrolidone-vinyl acetate copolymer (PVPVA) and hydroxypropyl methyl-cellulose (HPMC). The concentration of ketoconazole in each cup of the dynamic gastrointestinal model (DGIM) was measured using fiber optical probes. Molecular interactions between ketoconazole and PVPVA or HPMC were simulated by Materials Studio. The results demonstrated that PVPVA and HPMC improved and maintained the supersaturation of ketoconazole. PVPVA exhibited superior precipitation inhibitory effect on ketoconazole molecule aggregation due to slightly stronger van der Waals forces as well as unique electrostatic forces, thereby further enhancing in vitro drug absorption, which correlated well with in vivo drug absorption. Compared with a conventional dissolution apparatus paddle method, the DGIM improved the mean prediction error through the IVIVC from 19.30% to 9.96%, reaching the qualification criteria. In conclusion, the physiologically based multi-cup dissolution approach enables improved evaluation of supersaturation in gastrointestinal transportation of BCS IIB drug ketoconazole, enabling screening screen precipitation inhibitors and achieving qualified IVIVC for drug formulation studies.

Proniosomes for Oral Delivery of Aceclofenac: Impact of Paddle Versus Dialysis Methods on In vitro-in vivo Correlation (IVIVC) Predictions

Background: This study aims to assess the suitability of in vitro drug release methods, dialysis and paddle methods for predicting in vivo behaviour of Aceclofenac (ACE) proniosomes. Methods: ACE proniosomes are prepared using different carriers: glucose, maltodextrin and manni-tol by the slurry method. The release studies of ACE proniosomes formulations were performed us-ing the paddle, and dialysis methods while in vivo studies were performed in albino rats. Graphical presentation, model-dependent and model-independent approaches were applied to compare two dissolution methods. Results: More than 70% of the drug was released from ACE proniosomes over 60 min by paddle method while not more than 5% was released in the same period by dialysis method. The paddle method provides a reproducible and faster release, whereas poor drug release occurred with the di-alysis method. For the paddle method, lower values of similarity factor (f2) and greater differences in the dissolution efficiency (DE) amongst different formulations and in comparison, to that of the pure drug indicates that it is a more discriminative method compared to dialysis. The paddle method also illustrated high regression coefficients (r2) of 0.81, 0.998 and 0.975 for FN1, FN2, and FN3, respectively for level A IVIVC, while poor or no relation (r2 < 0.1) was detected in the case of dialy-sis method. Conclusion: Based on the results, the paddle method is concluded to be the more suitable method compared to the dialysis method for in vitro drug release studies of a novel dosage form such as proniosomes.

Comparison of pharmaceutical characteristics and membrane permeability of truvada combination tablets and its generic drugs

Pre-exposure prophylaxis (PrEP) prevents HIV infection through the daily administration of anti-HIV drugs, such as Truvada combination tablets (a combination of emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF)). However, since PrEP is not approved in Japan, generic drugs sold overseas are imported and used by individuals. Then, the present study investigated the pharmaceutical equivalence of two generic drugs of Truvada (Generic A and Generic B). Tablet properties were examined by X-ray diffraction and differential scanning calorimetry. The dissolution behaviors and membrane permeabilities of FTC and TDF were assessed by the dissolution test using the paddle method and a membrane permeation experiment using Caco-2 cell monolayers, respectively. The dissolution behaviors of FTC and TDF differed between Truvada and its generic drugs. Furthermore, the membrane permeation rates of FTC and TDF in Generic B were slower than those in Truvada, and the AUC of FTC in Generic B was significantly smaller than that in Truvada. Differences were observed in the dissolution behaviors and membrane permeabilities of FTC and TDF in generic drugs (particularly Generic B) from those in Truvada. Since there are concerns regarding the clinical implications of these results, further studies, including in vivo experiments, are needed to ensure the safety of generic drugs.

Preparation and Evaluation of Repaglinide Loaded Liposomes by Ether Injection Method

Repaglinide is a commonly used antidiabetic drug to treat type 2 diabetes mellitus. However, it does not always support a suitable dose regimen due to its low bioavailability and half-life. The purpose of this study was to develop and analyze repaglinide loaded control release liposomes to provide suitable dosage form to treat diabetes. Repaglinide loaded liposomes were prepared by modified ether injection method. According to the USP-II paddle method, in vitro dissolution studies of liposomes were performed for 8 hours in phosphate buffer (pH 7.4). The stability study was executed according to ICH guidelines under three different environmental conditions for 14 days. Additionally, the presence and size of liposomal vesicles was confirmed by microscopic observation. The formulations containing phosphatidylcholine and cholesterol at a molar ratio of 1:0.4 revealed the highest drug entrapment efficiency of 73.1% with an optimum stirring rate of 300 RPM. The pegylated liposomes (PEG400/1500) prolonged the drug loading capacity for the formulations compared to non-pegylated liposomes. On the contrary, the addition of nigella oil caused a decrease in entrapment efficiencies of the liposomes. Most of the formulations followed zero order kinetic model and supper class II release mechanism. In vitro dissolution showed controlled release pattern of the liposomes and maximum drug release after 8 hours was 92.64%. Additionally, all the liposomal formulations were found to be more stable at refrigeration temperature (5 ± 2ºC) where pegylated liposomes were most stable over 14 days at three different environmental conditions. Visual observation under an optical microscope, the vesicular structure of liposomes was confirmed. Dhaka Univ. J. Pharm. Sci. 22(1): 89-96, 2023 (June)

Phosphate buffer interferes dissolution of prazosin hydrochloride in compendial dissolution testing

The purpose of this study was to elucidate the lack of supersaturation behavior in the dissolution profile of prazosin hydrochloride (PRZ-HCl) in the compendial dissolution test. The equilibrium solubility was measured by a shake-flask method. Dissolution tests were performed by a compendial paddle method with a phosphate buffer solution (pH 6.8, 50 mM phosphate). The solid form of the residual particles was identified by Raman spectroscopy. In the pH range below 6.5, the equilibrium solubility in phosphate buffer was lower than that in the unbuffered solutions (pH adjusted by HCl and NaOH). Raman spectra showed that the residual solid was a phosphate salt of PRZ. In the pH range above 6.5, the pH-solubility profiles in the phosphate buffer solutions and the unbuffered solutions were the same. The residual solid was a PRZ freebase (PRZ-FB). In the dissolution test, PRZ-HCl particles first changed to a phosphate salt within 5 min, then gradually changed to PRZ-FB after several hours. Since the intestinal fluid is buffered by the bicarbonate system in vivo, the dissolution behavior in vivo may not be properly evaluated using a phosphate buffer solution. For drugs with a low phosphate solubility product, it is necessary to consider this aspect.

The Effect of Sampling Cannula on In Vitro Dissolution Testing with USP Paddle Method.

In vitro dissolution tests are widely used as quality control tools for drug products in development and manufacturing. Dissolution acceptance criteria are one of the important factors assessed during the regulatory review process. Understanding potential sources of variability is critical and a key to assuring reliable results are obtained when using a standardized system for in vitro dissolution testing. Sampling cannulas are commonly used to withdraw sample aliquots from dissolution medium and are potentially one of the testing factors that can contribute to variabilities in dissolution testing. However, there are still no clear requirements on the size or setting (intermittent or stationary) of sampling cannulas for dissolution testing. Thus, the objective of this study is to evaluate whether various sizes and sampling cannula settings yield different dissolution results using the USP 2 apparatus. Sampling cannulas with outer diameter (OD) ranging from 1.6mm to 9.0mm were used in dissolution testing with either intermittent or stationary setting to collect sample aliquots at multiple time points. The dissolution results at each time point were statistically analyzed for effects of both OD and setting of sampling cannula on drug release from 10mg prednisone disintegrating tablets. Dissolution results indicated both size and setting of the sampling cannula may cause significant systematic errors, even though the dissolution apparatus has been calibrated. The degree of interference in dissolution results was directly related to the OD of the sampling cannula. Size of sampling cannula and setting of sampling procedure should be documented in standard operating procedures (SOP) for dissolution testingduring method development.

Design and In-Vitro Evaluation of Compressed Kollidon® SR Based Naproxen Sodium Microcapsule: Effect of Talc

Naproxen sodium is a nonsteroidal anti-inflammatory drug (NSAID) with analgesic antipyretic properties. In this research work, naproxen sodium was encapsulated by solvent-evaporation technique using kollidon® SR as coating polymeric material to prolong the therapeutic duration of the drug. Four different concentrations of talc were used as additives to see the changes in drug release pattern from the compressed microcapsules. Scanning Electron Microscopy (SEM) was applied to study size and surface morphology of prepared microcapsules. UV-spectrophotometric method was applied to calculate the drug loading efficiency and the performance of the prepared dosage form was evaluated in terms of in-vitro dissolution studies according to USP paddle method (type 2) in 400 ml in phosphate buffer (pH 6.8) for 8 hours at 370 ± 50 C temperature at 50 rpm. Release of naproxen sodium from the compressed microcapsules was found to follow hixon crowell mechanism (R2=0.99). Hixon equation was used to calculate the release exponent value (n) which indicates the drug release behavior and the mean dissolution time T50% (MDT) for release rate. The surfaces of the microcapsules became smoother with the increase in talc amount and simultaneously decrease in drug release rate.
 Keywords: Naproxen sodium, Kollidon® SR, microcapsule, emulsion solvent evaporation technique, MDT (Mean Dissolution Time)

Physical Assessment and formulation development of Dome Matrix Controlled Release tablet of Diclofenac Sodium

In the last fifteen years where have significant acceleration in drug delivery research. In the early days of controlled release, development of pharmaceutical formulations was more idealized, with emphasis on the attainment of the illusive “zero-order release behavior”. When analyzing the swelling and release behavior of the Dome Matrix systems, it was demonstrated that the swelling behavior of the curved surfaces of the matrices strongly affected the drug release kinetics. The controlled release Dome matrix tablets containing Diclofenac sodium were prepared using a wet granulation process and polymers used xanthan gum, HPMC and Eudragit. Two different formulations were prepared; in first formulation the ratio was kept 60% active ingredient and 40% polymers subsequently in 2nd formulation 55% active ingredient 45% polymers. Precompression test angle of repose, Hausner’s ratio, Bulk Density, Tapped Density, Car’s Index were checked according to the specified standard procedure. All Physical Characteristics of dome tablets were analyzed. Drug release pattern was also analyzed by using USP apparatus II paddle method. The hardness, weight fluctuation, thickness, friability, drug content homogeneity, and in-vitro dissolution investigations of the manufactured controlled release tablets. All were examined and found within acceptable range. The F1 and F2 formulations performed well in tests and had a continuous drug release. The findings of this study showed that a polymer could be successfully used to formulate Diclofenac sodium Dome matrix tablets. The drug release was extended for 8 to 12 hours in all formulations using a drug to polymer ratio of 60:40, 55:45. The formulations are proved to have efficient drug release time. Keywords: Diclofenac sodium, Dome Matrix, Eudragit, Control release, Xanthan gum.

Formulation and Evaluation of Sustained Release Microcapsule of Metronidazole

The oral conventional metronidazole dosage forms have a short duration of action due to gastric emptying process, hence the treatment of ulcus pepticum using metronidazole become less effective. Due to retaining the dosage form in the stomach, a preparation form of sustained released drug delivery systems has been developed. The aim of this study was to developed a sustained released drug delivery systems of metronidazole using alginate and chitosan as polymers that could last longer in stomach. The formulation consisted of variatons in chitosan 0.5%, 0.75% and 1%. The drug released test was carried out using paddle method in simulated gastric medium pH 1.2 at 37°C. The dissolution test results showed that formula with 0.75% of chitosan giving the best sustained released effect and the kinetics drug realeased of microcapsule followed Higuchi order. Based on the results of the study, it can be concluded that microcapsules of metronidazole with a combination of alginate and chitosan can be prepared as sustained released formulation.

An In Vitro Dissolution Determination of Multi-Index Components in Tibetan Medicine Rhodiola Granules.

The composition of the Tibetan medicine Rhodiola granules (RG) is complex, and the overall quality of RG is difficult to determine. Therefore, establishing a method to determine the multi-component in vitro dissolution of RG is of great significance for quality control. This study uses the second paddle method of the fourth general rule 0931 from the Chinese Pharmacopoeia (2020 edition), compliant with apparatus 2 of the United States Pharmacopeia (USP). The dissolution apparatus was set to a rotation speed of 100 rpm with ultrapure water as the dissolution medium. A sample volume of 1 mL was collected at each timepoint. Furthermore, the cumulative dissolution of gallic acid, salidroside, and ethyl gallic acid in RG at different time points was determined by high-performance liquid chromatography (HPLC). Finally, the dissolution curves were drawn, and the curves were fitted to the GompertzMod, the Gompertz, the Logistic, and the Weibull equations. The results showed that the cumulative dissolution of gallic acid in RG was over 80% at 1 min, the cumulative dissolution of salidroside and ethyl gallic acid was over 65% at 5 min, and the cumulative dissolution of each index component decreased after 30 min. The curve fitting demonstrated that the GompertzMod equation was the best-fitting model for each index component of RG. In conclusion, the dissolution test method described in this protocol is simple, accurate, and reliable. It can characterize the dissolution behavior of the index components in RG in vitro, which provides a methodological reference for quality control of RG and quality evaluation of other ethnic compounds.