Differences in the release of active ingredients in different dosage forms
Gel is a thick liquid or semi-solid preparation with gel characteristics made from a raw drug and excipients that can form a gel; and microemulsion, as a new type of dosage form, utilizes surfactants to enable the oil and water phases in the preparation to exist harmoniously, so that the active ingredient stays in the aqueous phase or the oil phase.
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1. Overview of Dosage forms
A gelling agent refers to a thick liquid or semi-solid preparation with gel-like properties, which is made from a raw drug and excipients that can form a gel. Microemulsions, as a new type of dosage form, utilize surfactants to enable the harmonious coexistence of the oil phase and the water phase in the preparation, allowing the active ingredients to remain in the water phase or the oil phase. These two dosage forms, due to their excellent stability, are used as common dosage forms in drug preparations.
However, as a part of semi-solid preparations, gels and microemulsions also comply with the relevant guidelines for semi-solid preparations. The performance evaluation of the preparations is based on the in vitro release capacity as the evaluation index.
2. In vitro release test
In the process of preparing preparations, it is often necessary to take into account the influence of dosage forms on the release of active ingredients in the body. The same active ingredient may exhibit completely different release effects in different dosage forms. In order to get the active ingredient into the body, It is necessary to select the appropriate dosage form so that the active ingredients can have a good release capacity.
3. Case sharing of in vitro release tests
This time, we will use the Ruituo RT800 automatic sampling transdermal diffusion system to present a case study on the in vitro release of the same active ingredient in two different dosage forms.
Experimental methods and test parameters:
Test system: Automatic sampling transdermal diffusion system
Diffusion cell: A standard Franz vertical diffusion cell with an inner aperture of 15mm
Sample loading volume: approximately 1 mL
Temperature: 37℃±0.5
Sampling time: 0.25, 0.5, 1, 2, 3, 4 hours
HPLC detection parameters:
Detector: UV 265nm
Flow rate: 1.0 mL/min
Mobile phase: Acetonitrile - sodium dihydrogen phosphate solution
Chromatographic column: Intersil ODS-3 5μm
Results
In this test, we examined the differences in the in vitro release behavior of the same active ingredient in different dosage forms under the same test conditions. The test results are as follows:
- Investigation on the differences in drug release caused by different dosage forms
The release rate of the drug in the sample is expressed by the cumulative drug release amount (μg/cm ²) and the square root of time (t) (i.e., Higuch's formula: M=kt1/2), where the k value represents the drug release rate. The results are shown in Figure 1. The release amount of active ingredient was different in different dosage forms, and the gel formulation group had a higher release amount in all sampling points.
Figure 1. In addition to the Dosage of drug release, the drug release rate can also reflect the effect of different preparations on the release of the same active ingredient. The drug release rate of the gel is 12711, and that of the microemulsion is 1139.5
2.Repeatability test
To ensure that the test results accurately reflect the differences among samples, it is necessary to examine the test conditions. The relevant guidelines for the validation of analytical methods in the ChP state that the purpose of the validation of analytical methods is to prove that the established method is suitable for the corresponding testing requirements. The key indicator for verification is repeatability.
The cumulative release curves of the two experiments have different coincidence degrees under the six parallel experiments. The relative standard deviations of the cumulative drug release at the sampling endpoint were 3.52% and 1.5% respectively. It can be seen that different preparations have different abilities to maintain good repeatability in experiments
3. Conclusion
In the process of choosing the appropriate dosage form, the drug release capacity demonstrated by different dosage forms can directly affect the final experimental results and conclusions. Therefore, in vitro drug release experiments, the selection of dosage forms for active ingredients should take into account the impact of dosage forms on drug release. For this purpose, appropriate instruments and equipment are needed to provide good reference opinions for the selection of dosage forms.
From the above case, it can be seen that the automatic sampling transdermal diffusion system can provide strong and favorable support for the in vitro release research of drugs. Moreover, under reasonable and appropriate release conditions, it can compare the cumulative drug release amount and cumulative drug release rate among different dosage forms of the same active ingredient, significantly differentiating the differences among different dosage forms.
