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Jan. 03, 2019

Dissolution basket specifications and inquiry links: Dissolution basket

Dissolution sinker specifications and inquiry links: Dissolution sinker

What is the dissolution rate?


We are familiar with the application of dissolution sinker and USP basket (dissolution basket) in the dissolution test. But what is dissolution test?


Dissolution refers to the rate and degree of dissolution of drugs from solid preparations such as tablets, capsules, and granules under specified conditions.

It is an in vitro test to simulate the disintegration and dissolution of oral solid preparations in the gastrointestinal tract. It is an important index for evaluating and controlling the quality of pharmaceutical preparations. It plays an important role in evaluating the batch quality of the preparation, optimizing the prescription and preparation process, and ensuring the consistency of product quality before and after the change of the prescription process.


In this process, some tools are sometimes needed, such as a dissolution sinker.


In the "dissolution determination method" included in the appendix of the Chinese Pharmacopoeia, the apparatus, determination methods and results from determination standards of the basket method (one method) and the paddle method (two methods) are specified in detail.


However, how to study and establish an effective dissolution test method is a more concerned issue for drug developers and producers.


Understanding Physical and Chemical Properties of APIs and Pharmaceuticals


Before establishing a dissolution test method, it is necessary to first understand the physicochemical properties of APIs and preparations.

For APIs, there are two aspects to be understood. One is the solubility of drugs in different pH conditions, or in different media. The second is the stability of drugs in solution.


Because the dissolution test method requires that the drug can meet the requirement of leaky groove condition in the selected medium, it is important to know the solubility under different pH conditions for the choice of medium.


It should be noted that the effects of surfactants, pH, and buffer on the solubility and stability of drugs should be evaluated when the leaky tank conditions are achieved by adjusting the composition of media (such as surfactants, pH, buffer, etc.).


The determination of the solubility curve of the substance should be carried out at 37 1 and the solubility of the drug in the aqueous medium with pH 1.0_7.5 should be determined.

The number of pH values determined depends on the ionization characteristics of the drug. For example, when the pKa of the drug is 3 5, the solubility of the drug should be determined at pH=pka, pH=pka+1, pH=pka-1, pH=1, and pH=7.5. The number of determination of pH value should meet the need of drawing the solubility curve of pH value accurately.


The solubility values at each pH are determined at least, and the number of times of determination is increased according to the deviation of the experimental results.

Buffers contained in Pharmacopoeia can be used for solubility determination. If the physicochemical properties of these buffers are not suitable for the determination of drug solubility, other buffers can be used instead.


The pH value of the solution should be validated when the drug is added to the buffer. In addition to the traditional shaking flask method, other methods can be used to determine the equilibrium solubility of the tested drugs if there are experimental data to prove that other methods can be used.

The concentration of drugs in buffer solution should be determined by an experimental method with good specificity and reproducibility, which can effectively separate the prototype drug from its degradation products.


For the tablets, the important factors that may affect the dissolution are coating condition, hardness, fragility, disintegration time, solvents in the prescription and other excipients.

Excipients sometimes affect the speed and extent of drug absorption, such as large doses of surfactants (such as polysorbate 80) usually increase the solubility of drugs and accelerate the dissolution of drugs.


The tablets are easy to float in the medium when using a lighter weight or waxy excipients. The uniformity of the results determined by basket method is better.


Selection of dissolution apparatus, dissolution sinker, and dissolution basket

- Difference between paddle and basket in dissolution


This is the key content of this blog. There are also introductions about the dissolution sinker and the dissolution basket.


The choice of dissolution instrument can be based on the formulation design and the actual behavior of the preparation in vitro dissolution system.

The methods contained in the appendix to the Pharmacopoeia can be selected, or other methods can be selected.


For example, some microspheres and implants can be tested for dissolution by the rotating bottle or the static tubes. For the use of the appendix of the non-pharmacopeia for inspection, sufficient experimental data must be provided to prove that the method used is more advantageous than the method contained in the pharmacopeia.


The methods included in the appendix of the Pharmacopoeia are the rotating basket method (one method) and the paddle method (two methods).

Basket method is often used in capsules and tablets. The paddle method is often used in tablets and capsules.

In some cases, increasing rotational speed (such as propeller method choosing 75rpm-100rpm) is helpful to establish a meaningful dissolution test method.


In the American Pharmacopoeia, a variety of dissolution test methods besides the basket method and paddle method are also included.


For the dissolution test of water-insoluble pharmaceutical preparations, in order to meet the leaky tank conditions, foreign countries also recommend large volume solutions (such as 2L or 4L), which are different from the requirements of the appendix of Chinese Pharmacopoeia.


Dissolution Basket


For the dissolution test by the revolving basket method, the size of the dissolution basket should conform to the provisions of the appendix of the Pharmacopoeia, and the size should be uniform.

Dissolution basket meshes size: 40 mesh.

Yes, if there is sufficient experimental data to support, if necessary, the screen aperture of the basket can also be modified, using 10-20 mesh screen (Need to customize the dissolution basket).


Dissolution Sinker


For the blocked basket sieve in the dissolution process of tablets or capsules, the dissolution test should be changed to paddle method(dissolution sinker).


In the process of propeller inspection, if tablets or capsules float on the liquid surface, the dissolution sinker can be used. Help to locate the preparation in the central position.


For film-coated tablets and soft capsules adhering to the wall of containers, dissolution sinker or dissolution baskets can also be used.


For the use of the dissolution sinker prescribed by the non-pharmacopeia, it is necessary to explain the reasons and detailed preparation methods.

At the same time, attention should be paid to providing detailed experimental data to illustrate the rationality of the choice of dissolution sinker, including comparing the use or non-use of dissolution sinker, and the influence of different dissolution sinker on dissolution behavior.


Because the dissolution sinker may have a significant impact on drug dissolution behavior, the dissolution sinker may also be part of the verification of dissolution test methods.


Selection of Speed (dissolution sinker and dissolution basket)


For general preparations, the rotational speed of the rotary basket method is generally 50 rpm-100 rpm, and that of the propeller method is 50 rpm-75 rpm. For dry suspension, 25 rpm-50 rpm is usually chosen.


If the dissolution data under other rotating speed conditions are compared with those under the above conventional rotating speed conditions or supported by other tests, it is proved that changing rotating speed is necessary, and other rotating speeds can also be selected.


For example, in the U.S. Pharmacopoeia, the rotation speed of the basket method also has a choice of 150 rpm.

If the paddle method and 50rpm are used to find the agglomeration and accumulation of the preparation, the rotational speed can be increased to 75rpm to reduce the accumulation. On the basis of sufficient research, it is also possible to select 100rpm.


However, rotational speeds below 25 rpm and over 150 RPM are generally unacceptable, because rotational speeds below 25 RPM lead to inconsistent hydrodynamic behavior, while rotational speeds above 150 RPM lead to hydrodynamic disorder.


Medium Selection


The selection of dissolution media is based on drug solubility and formulation specifications to ensure that the leaky groove conditions are met (defined as the volume of the medium at least three times the saturated concentration of the drug).


However, if the selected medium is proved to be more resolving or supported by other sufficient data, such as in vivo and in vitro correlation, the medium that does not meet the leaky groove condition can also be selected.


In order to obtain reliable dissolution data, surfactants can be considered, but water-organic solvent dissolution systems are generally not encouraged.

If it can be proved that water-soluble media alone can not obtain in vivo and in vitro correlation, and water-organic solvent dissolution system can achieve in vivo and in vitro correlation, such media can also be used.


Dissolved medium is generally recommended as the preferred water in China. But in fact, because:


(1) Water quality from different sources is different

(2) It is difficult to check the pH of the water because the pH of the water is different every day. Even in the process of determination, the pH of the raw material and excipients can change.

(3) The surface tension of water may vary with the excipients in the prescription.


Therefore, although pure water is widely used as a dissolution medium, pure water is not an ideal dissolution medium.

However, because water is cheap and readily available, water is an appropriate medium for pharmaceutical preparations whose dissolution rate is independent of pH.

At the same time, if water has been selected as the testing medium in the national drug standards or Pharmacopoeia standards, it is generally not necessary to use other media unless there is a definite reason.


The dissolution behavior of oral preparations should be investigated in the range of pH 1.2-6.8.

In the establishment stage of the method, it is necessary to check whether the pH changes before and after dissolution.


For drugs that can dissolve quickly in the stomach and have high permeability, gastric emptying time may be the limiting step of absorption. For these drugs, dissolution test mainly proves that drugs can dissolve quickly in gastric juice.

For drugs mainly dissolved in the intestine, such as insoluble drugs, weak acids, the choice of a higher pH range (such as pH 6.8 artificial intestinal fluid) may be the appropriate medium.


"Fasting" and "eating" states may also have significant effects on drug absorption and solubility. Some media simulating "fasting" and "eating" states are reported in the literature. These media reflect the changes of pH, bile salt concentration and osmotic pressure after eating. It is mainly used to establish in vivo-in vitro correlation in the development stage of preparations, or to evaluate the possible effects of food, but not for product quality control.


The biopharmaceuticals classification system based on the solubility and permeability of drugs will call the dissolution medium which has a certain correlation with the body as the related medium.

To determine whether the dissolution medium belongs to the bio-related medium depends mainly on the absorption site of the preparation and whether the dissolution or permeation process is the rate-limiting step of absorption.

Sometimes, the dissolution conditions of biologically related media may be different from those used for registration declaration, and the sampling time may also be different.


That's the end of this blog.


There are not many real producers in China for dissolution sinker and dissolution basket. ZHEHAN is a leader in both quality and price.


If you are interested in our dissolution sinker, you can leave us a message.


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