What Is Drug Stability Analysis?

The basic requirements of pharmaceutical preparations are safety, efficacy, and stability. Drug stability means that a drug product should maintain the same properties and characteristics as it was at the time of production and within the specified time frame. The stability of pharmaceutical preparations directly affects the effectiveness and safety of drugs. Therefore, it is of great significance to study the stability of pharmaceutical preparations to ensure product quality, safety, and effectiveness.

Research Scope on Drug Stability Analysis

Chemical stability refers to changes in drug content (or potency) due to chemical reactions such as hydrolysis and oxidation.

Physical stability mainly refers to changes in physical properties, such as changes in appearance, odor, uniformity, solubility, and redispersibility.

Biological and Microbiological Stability is a must to ensure that pharmaceutical preparations are not spoiled after microbial contamination.

Factors Affecting the Stability of Pharmaceutical Preparations

Many factors affect the stability of drugs, for example, each active ingredient in the drug, each excipient in the preparation, packaging materials, and storage environments such as temperature, humidity, light, pH and air.

Ways to Improve Drug Stability

Cyclodextrin–Drug Inclusion Complexes

Cyclodextrins (CD) are a kind of oligosaccharides whose molecules are hollow and cylindrical. CD can be used as the host, which can incorporate guest molecules of a certain size and shape to form a special inclusion complex. Common CDs are α-, β-, and γ-, which have stable crystal structures. Among them, β-CD and its derivatives are new drug inclusion materials developed in recent years, because of their moderate cavity inner diameter, strong inclusion force, mass production of raw materials, and economical availability. The hydrophilic group of β-CD can improve the solubility, dissolution rate and bioavailability of the drug after the inclusion of the poorly soluble drug, and the hydrophobic group can control the release rate of the drug after forming an inclusion complex with the water-soluble drug.

The CD inclusion compound is equivalent to a molecular capsule. The drug molecule is separated and included in the cavity of the CD, and thus be protected from the attack of reactive molecules in the external environment, and avoid the hydrolysis, oxidation, isomerization, and polymerization of the drug molecule.

Film Coating

Film coating is to uniformly coat the polymer solution or dispersion on the surface of solid preparations such as tablets, capsules, granules, and pellets to form a fine-grained integrity film layer. The coating material is mainly made of suitable polymers with carboxylic acid groups dissolved in alkaline aqueous solution. The film coating can effectively control the moisture absorption and volatilization of the drug, and the dissolution rate has not changed significantly, which greatly improves the stability of the preparation.

Pharmaceutical Polymorphic Transformation

The same drug with different crystal forms has significant differences in solubility, dissolution rate, melting point, density, hardness, appearance, and bioavailability, which affects the stability, bioavailability and efficacy of the drug. The stable form has a small entropy value, high melting point and the best chemical stability, but the dissolution rate and solubility are the smallest, so the bioavailability is also poor. The unstable form is the opposite, while the metastable form is between the stable type and the unstable type. Polymorphs can be phase-transformed through solvent-mediated transitions.

Freeze Drying Technology

The freeze-drying technology was mainly used for the preservation of biological materials in the early stage. This technology can keep the original physical and chemical properties and physiological activity of the drug. In addition, the unique loose porous structure of the freeze-dried preparation can make the drug easy to restore the activity, and the freeze-dried preparation has a low water content, which is easy to be stably stored for a long time and maintain its stability.

Drug Microencapsulation

Microcapsules are tiny particles that use film-forming materials (capsule materials) to encapsulate active substances such as solids, liquids, or gases. Microencapsulation is a new technology that has developed rapidly in recent years. At present, there are microencapsulated preparations of more than 30 types of drugs such as antibiotics, vitamins, anticancer drugs, contraceptives, and antipyretic analgesics on the market. After the drug is microencapsulated, it can be made into different dosage forms such as powder, tablet, granule, capsule, and injection.

Summary

The stability of a pharmaceutical formulation refers to its ability to retain physical, chemical, biological and microbiological stability. A thorough analysis of drug stability plays an extremely important role in quality control and drug efficacy guarantee.