Everything below concerns Lyophilization. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-06-30. Where a claim depends on a specific study, the study is described rather than over-claimed.
A formulation often contains excipients that protect the active ingredient during freezing and drying. Bulking agents provide structure, while lyoprotectants stabilize sensitive molecules. The freezing step can produce ice crystals whose size and distribution affect the drying rate, and cycle design includes freezing, annealing, and drying phases. If the product temperature rises above a critical value, the cake may collapse or lose its porous structure. Successful lyophilization therefore depends on the interaction between formulation, equipment, and cycle design.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen to convert liquid water into ice. Next, the pressure is reduced below the triple point of water so that ice changes directly into vapor without passing through a liquid phase. This step is called primary drying. The result is a porous solid or cake that retains the original shape of the frozen solution.
After primary drying, secondary drying removes water that remains bound to the material. This stage raises the shelf temperature while maintaining low pressure, which encourages desorption of unfrozen water. Residual moisture can be reduced to a low percentage, improving stability for many products. The process parameters, including freezing rate, shelf temperature, and chamber pressure, influence the final pore structure and reconstitution behavior. Control of these variables helps prevent collapse or meltback during drying.
The process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilization is the American spelling; lyophilisation is British |
| Primary drying mechanism | Sublimation of ice | Occurs under vacuum below the triple point |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product and equipment |
| Typical shelf temperature during freezing | -40 to -20 °C | Lower temperatures may be used for labile products |
| Resulting product form | Porous cake or powder | Appearance depends on formulation and cycle |
The physics of freeze-drying couples heat transfer, mass transfer, and phase change. Heat supplied through the shelf must reach the sublimation front without melting the ice or degrading the product. Water vapor then travels through the already dried layer and leaves the chamber, where low pressure and cold traps keep it from returning. The dried layer acts as a resistance to vapor flow, so drying rate changes as the front recedes. Open questions remain about how pore structure and formulation heterogeneity affect drying uniformity at larger scales.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and concentrates dissolved solids. Primary drying then lowers chamber pressure so ice changes directly into vapor without passing through a liquid phase. Secondary drying raises the shelf temperature to remove bound water that remains after ice sublimation. The result is a dry, porous structure that can be reconstituted later.
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
=== Acidity/basicity === Ionic compounds containing hydrogen ions (H+) are classified as acids, and those containing electropositive cations and basic anions ions hydroxide (OH−) or oxide (O2−) are classified as bases. Other ionic compounds are known as salts and can be formed by acid–base reactions. Salts that produce hydroxide ions when dissolved in water are called alkali salts, and salts that produce hydrogen ions when dissolved in water are called acid salts, e.g. sodium hydrogen selenite (NaHSeO3). If the compound is the result of a reaction between a strong acid and a weak base, the result is an acid salt. If it is the result of a reaction between a strong base and a weak acid, the result is a base salt. If it is the result of a reaction between a strong acid and a strong base, the result is a neutral salt. Weak acids reacted with weak bases can produce ionic compounds with both the conjugate base ion and conjugate acid ion, such as ammonium acetate. Some ions are classed as amphoteric, being able to react with either an acid or a base. This is also true of some compounds with ionic character, typically oxides or hydroxides of less-electropositive metals (so the compound also has significant covalent character), such as zinc oxide, aluminium hydroxide, aluminium oxide and lead(II) oxide.
The radio source PSR J1928+15 (observed in 2005 near the Galactic disk, at a frequency of 1.44 GHz, at Arecibo) could be of extraterrestrial origin. James and Dominic Benford consider three scenarios in which the cost factor is taken into account. If the source is cost-optimized, it belongs to a civilization of Type 0.35 (the Earth being of Type 0.73). If it is not cost-optimized and operates with a small antenna, the Type is 0.86. With a large antenna, it would be from a Type 0.66. Using this cost/efficiency method, it can be estimated that low-intensity sources may be the most prevalent, but also the most difficult to observe.
== Effects == Baikiain is hypothesized to be the causative agent of illnesses resulting from consumption of food products containing tara flour. In several cases documented in 2022 people became ill after consuming meals containing tara flour with high concentrations of Baikian (3% dry weight). People experienced acute gastrointestinal and liver disease with clinical signs of hepatotoxicity. Baikiain was found not to harm mammalian or human cells in culture but did cause liver injury and depletion of glutathione in rodent models.
∗The findings are a comparison between e-cigarette daily usage and the regulatory limits of chronic Permissible Daily Exposure from inhalation medications outlined by the US Pharmacopeia for cadmium, chromium, copper, lead and nickel, the Minimal Risk Level outlined by the Agency for Toxic Substances and Disease Registry for manganese and the Recommended Exposure Limit outlined by the National Institute for Occupational Safety and Health for aluminum, barium, iron, tin, titanium, zinc and zirconium, referring to a daily inhalation volume of 20 m3 air and a 10-h volume of 8.3 m3; values are in μg.
Sources: en.wikipedia.org
== Contraindications == The two contraindications to taking ezetimibe are a previous allergic reaction to it, including symptoms of rash, angioedema, anaphylaxis, and severe liver disease, especially when taken with a statin. Ezetimibe may have significant medication interactions with ciclosporin and with fibrates other than fenofibrate.
Glycocyamine kinase (EC 2.7.3.1), which catalyses the transfer of phosphate from ATP to guanidoacetate. Arginine kinase (EC 2.7.3.3), which catalyses the transfer of phosphate from ATP to arginine. Taurocyamine kinase (EC 2.7.3.4), an annelid-specific enzyme that catalyses the transfer of phosphate from ATP to taurocyamine. Lombricine kinase (EC 2.7.3.5), an annelid-specific enzyme that catalyses the transfer of phosphate from ATP to lombricine. Smc74, a cercaria-specific enzyme from Schistosoma mansoni. Creatine kinase (EC 2.7.3.2) (CK), which catalyses the reversible transfer of high energy phosphate from ATP to creatine, generating phosphocreatine and ADP. Creatine kinase plays an important role in energy metabolism of vertebrates. There are at least four different, but very closely related, forms of CK. Two isozymes, M (muscle) and B (brain), are cytosolic, while the other two are mitochondrial. In sea urchins there is a flagellar isozyme, which consists of the triplication of a CK-domain. A cysteine residue is implicated in the catalytic activity of these enzymes and the region around this active site residue is highly conserved. ATP:guanido phosphotransferases contain a C-terminal catalytic domain which consists of a duplication where the common core consists of two beta-alpha-beta2-alpha repeats. The substrate binding site is located in the cleft between N and C-terminal domains, but most of the catalytic residues are found in the larger C-terminal domain.
Palmitoyl pentapeptide-4 (Matrixyl, called palmitoyl pentapeptide-3 before 2006) is a matrikine used in anti-wrinkle cosmetics. It was launched in 2000 as an active ingredient for the personal care industry under the trade name Matrixyl by the French cosmetic active ingredient manufacturer Sederma SAS.
In crystallography, polymorphism is the phenomenon where a compound can crystallize into more than one crystal structure; in the case of elements the term allotropy is sometimes used. An example of polymorphism is titanium dioxide (TiO2), which occurs in four known natural polymorphic forms (minerals with the same composition but different structure): brookite (orthorhombic), akaogiite (monoclinic), anatase (tetragonal) and rutile (tetragonal). Eilhard Mitscherlich discovered polymorphism ("dimorphism") in his studies of sodium phosphate (1821) and sulphur (1823). In the 1830s the development of the microscope enhanced observations of polymorphism and aided Moritz Ludwig Frankenheim's studies. Frankenheim was able to demonstrate methods to induce crystal phase changes, for example the use of solvents or physical scratching, and formally summarized his findings on the nature of polymorphism. Soon after, the more sophisticated polarized light microscope came into use, and it provided better visualization of crystalline phases allowing crystallographers to distinguish between different polymorphs. The hot stage was invented and fitted to a polarized light microscope by Otto Lehmann in about 1877. This invention helped crystallographers determine melting points and observe polymorphic transitions. The first polymorphic organic substance, benzamide, was discovered by Friedrich Wöhler and Justus von Liebig in 1832. In 1870 Paul Groth defined wikt:morphotropy as the state of two crystals whose similar physical structure is due to similar chemical composition.
Further work by Crick and co-workers showed that the genetic code was based on non-overlapping triplets of bases, called codons, allowing Har Gobind Khorana, Robert W. Holley, and Marshall Warren Nirenberg to decipher the genetic code. These findings represent the birth of molecular biology.
Sources: en.wikipedia.org
Lyophilization removes water by sublimation from a frozen material, while evaporation changes liquid water into vapor. The low-pressure freezing step avoids the liquid phase and can preserve heat-sensitive structures.
Vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor. It also helps remove water vapor from the product chamber and shortens primary drying.
Many aqueous solutions and suspensions can be freeze-dried, but some formulations collapse or do not form a stable cake. The process requires careful formulation and cycle development.
The main change is sublimation, in which ice becomes water vapor without melting into liquid water. This occurs when the chamber pressure is held below the vapor pressure of ice while mild heat is supplied. The result is a dry, porous solid that retains much of its original shape.