Everything below concerns primary drying. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-04-05. Where a claim depends on a specific study, the study is described rather than over-claimed.
Lyophilization, also known as freeze-drying, is a process that removes water from a material by freezing it and then reducing pressure to allow ice to sublimate directly into vapor. The method begins with a freezing step that solidifies the water content. Next, primary drying lowers the pressure below the triple point of water, enabling sublimation without passing through a liquid phase. A final secondary drying step removes bound water through desorption. This sequence produces a dry, porous cake that can be reconstituted later.
The process relies on the phase diagram of water, where the triple point marks the conditions at which ice, liquid water, and vapor coexist. By maintaining pressure below this point, typically around 0.01 to 0.1 millibar, sublimation becomes the dominant mechanism. Formulations often include excipients such as sugars or polymers that act as lyoprotectants and bulking agents. These additives help preserve the structure of the active ingredient and prevent collapse during drying. The choice of excipient and freezing rate influences the final cake morphology and stability.
Freezing determines ice crystal structure and pore size, which affect drying speed and product uniformity. Rapid freezing creates small crystals, while slow freezing creates larger crystals and often faster sublimation. During primary drying, chamber pressure is held below the vapor pressure of ice, and shelf temperature supplies heat for sublimation. The ice front recedes, leaving a porous matrix. Thermal limits such as collapse and eutectic temperatures set safe boundaries for formulation. These limits vary with solute composition and concentration.
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.
| Property | Value | Notes |
|---|---|---|
| Common name | Freeze-drying | Lyophilization is the technical synonym. |
| Typical chamber pressure | 0.01–0.1 mbar | Below the triple point of water. |
| Primary drying temperature | −40 to −10 °C | Depends on formulation and equipment. |
| Residual moisture | 1–5% | Target for many pharmaceutical products. |
| Typical equipment | Vacuum freeze-dryer | Includes drying chamber and condenser. |
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.
Formulation composition influences whether freeze-drying produces an intact cake or a collapsed mass. Excipients such as sugars and polymers can raise the collapse temperature and provide bulk during drying. The critical temperature for primary drying is often the collapse temperature or the glass transition temperature of the maximally concentrated phase. If the product temperature exceeds this threshold, the frozen matrix may soften and lose structure. Established practice therefore links shelf temperature and chamber pressure to the formulation's thermal properties.
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.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen so that water becomes ice; then the surrounding pressure is lowered below the vapor pressure of ice. Heat is applied gently so ice changes directly to vapor without passing through a bulk liquid phase. The vapor is collected on a cold condenser, leaving a dry porous matrix. This process differs from simple evaporation because the material remains frozen during the main drying stage.
Later, some eukaryotes that already contained mitochondria also engulfed cyanobacteria-like organisms, leading to the formation of chloroplasts in algae and plants. This is known as primary endosymbiosis.
The real chromatographic analysis starts with the introduction of the sample onto the column. The development of capillary gas chromatography resulted in many practical problems with the injection technique. The technique of on-column injection, often used with packed columns, is usually not possible with capillary columns. In the injection system in the capillary gas chromatograph the amount injected should not overload the column and the width of the injected plug should be small compared to the spreading due to the chromatographic process. Failure to comply with this latter requirement will reduce the separation capability of the column. As a general rule, the volume injected, Vinj, and the volume of the detector cell, Vdet, should be about 1/10 of the volume occupied by the portion of sample containing the molecules of interest (analytes) when they exit the column. Some general requirements which a good injection technique should fulfill are that it should be possible to obtain the column's optimum separation efficiency, it should allow accurate and reproducible injections of small amounts of representative samples, it should induce no change in sample composition, it should not exhibit discrimination based on differences in boiling point, polarity, concentration or thermal/catalytic stability, and it should be applicable for trace analysis as well as for undiluted samples. However, there are a number of problems inherent in the use of syringes for injection. Even the best syringes claim an accuracy of only 3%, and in unskilled hands, errors are much larger.
Cut flowers have become a part of international trade and an active economic engine in a number of tropical countries (for instance in Kenya). Research and markets has estimated that the cut flower global market will reach a size of US$50.1 billion by 2030 from its current estimate of US$33.3 billion for 2022. Roses are projected to increase at a 5.9% compound annual growth rate, while chrysanthemum and gerbera will increase by 5.3% over the next eight years. Royal FloraHolland in Aalsmeer, Netherlands, is the largest flower market in the world. Flowers with a value of over US$4 billion pass through the market each year. In 2019, the export value of cut flowers was €4,200 million from the EU, Colombia exports were €1,235 million, Ecuador exports were €721 million, Kenya exports were €487 million and Ethiopia exports were €180 million, while US exports were only €14 million compared to €1,052 million in imports. Union Fleur, a European international flower trade association, represents the interests of Austria, Colombia, Denmark, Ethiopia, Germany, Italy, Kenya, Netherlands, Sweden, Turkey, Uganda, and the United States. Most of Royal FloraHolland exports go to European neighbors. Cut flower exports from China rose from US$71.4 million in 2011 to US$162.1 million in 2022, primarily from Yunnan Province where there are 300,000 farmers cultivating 1.5 million hectares of flowers. Overall production is much higher because 90% of flowers are sold in China. Most cut flowers are sold through the Dounan Flower Market in Kunming, Yunnan, China.
Lilly patented secobarbital in 1934 and marketed the barbiturate under the brand name Seconal. Seconal was used primarily as a sedative and hypnotic, but barbiturates were later largely supplanted by benzodiazepines. Lilly continued to manufacture and sell secobarbital until the early 2000s, when its marketing and manufacturing rights were transferred to Ranbaxy Pharmaceuticals. During World War II, the company expanded production to a new high, manufacturing merthiolate, an organomercury compound, and penicillin, a beta-lactam antibiotic. Lilly also cooperated with the American Red Cross to process blood plasma. By the end of World War II, the company had dried over two million pints of blood, "about 20 percent of the United States' total". Merthiolate, first introduced in 1930, was an "antiseptic and germicide" that became a U.S. Army standard issue during World War II. During World War II, Lilly manufactured products for military use, including aviator survival kits and seasickness medications for the D-Day invasion as well as penicillin. During World War II, Lilly produced penicillin and other antibiotics, "antimalarials," blood plasma, encephalitis vaccine, typhus and influenza vaccine, gas gangrene antitoxin, Merthiolate, and Iletin (Insulin, Lilly). The company was a partner of the U.S. government on large-scale production of penicillin. International operations expanded even further during World War II. In 1943, Eli Lilly International Corp. was formed as a subsidiary to encourage business trade abroad.
Sources: en.wikipedia.org
Diclofenac consumption has been associated with significantly increased vascular and coronary risk in a study including COX-2 inhibitors, diclofenac, ibuprofen and naproxen. Upper gastrointestinal complications were also reported. Major adverse cardiovascular events were increased by about a third by diclofenac, chiefly due to an increase in major coronary events. Compared with placebo, of 1000 patients allocated to diclofenac for a year, three more had major vascular events, one of which was fatal. Vascular death is increased significantly by diclofenac. In October 2020, the US Food and Drug Administration (FDA) required the prescribing information to be updated for all nonsteroidal anti-inflammatory medications to describe the risk of kidney problems in fetuses that result in low amniotic fluid.
== Function == cADPR is a cellular messenger for calcium signaling. It stimulates calcium-induced calcium release at lower cytosolic concentrations of Ca2+. The primary target of cADPR is the endoplasmic reticulum Ca2+ uptake mechanism. cADPR mobilizes Ca2+ from the endoplasmic reticulum by activation of ryanodine receptors, a critical step in muscle contraction. cADPR also acts as an agonist for the TRPM2 channel, but less potently than ADPR. cADPR and ADPR act synergistically, with both molecules enhancing the action of the other molecule in activating the TRPM2 channel. Potentiation of Ca2+ release by cADPR is mediated by increased accumulation of Ca2+ in the sarcoplasmic reticulum.
In 2001, a study of thagomizers by McWhinney et al. showed a high incidence of trauma-related damage. This too supports the theory that the principal function of the thagomizer was defense in combat. There is also evidence for a defense function in the form of an Allosaurus tail vertebra with a partially healed puncture wound that fits a Stegosaurus tail spike. This usage of the thagomizer would be similar to defensive behaviors in some extant lizards with tail spikes, such as the giant girdled lizard. The species of stegosaur known as Stegosaurus stenops had four dermal spikes, each about 60–90 cm (2–3 ft) long. Discoveries of articulated stegosaur armor show that, at least in some species, these spikes protruded horizontally from the tail, not vertically as is often depicted. Initially, Othniel Charles Marsh described S. armatus as having eight spikes in its tail, unlike S. stenops. However, recent research re-examined this and concluded this species also had four.
== Contraindications == Contraindications of psilocybin are mostly psychiatric conditions that increase the risk of psychological distress, including the rare adverse effect of psychosis during or after the psychedelic experience. These conditions may include history of psychosis, schizophrenia, bipolar disorder, or borderline personality disorder. Further research may provide more safety information about the use of psilocybin in people with such conditions. It is notable in this regard that psilocybin and other psychedelics are being studied for the potential treatment of all the preceding conditions. In the case of bipolar disorder, there are concerns that psychedelics may trigger a switch into mania. Psilocybin is considered to be contraindicated in women who are pregnant or breastfeeding due to insufficient research in this population. There are transient increases in heart rate and blood pressure with psilocybin, and hence uncontrolled cardiovascular conditions are a relative contraindication for psilocybin. Serotonin 5-HT2A receptor antagonists such as atypical antipsychotics and certain antidepressants may block psilocybin's hallucinogenic effects and hence may be considered contraindicated in this sense. Monoamine oxidase inhibitors (MAOIs) may potentiate psilocybin's effects and augment its risks.
=== Solvent process === The process involves transesterification of sucrose and triglycerides under a basic condition at 90 °C. DMF was used as a solvent at first, but was later substituted with dimethyl sulfoxide or DMSO, which is less hazardous and cheaper. This process produces a mixture of sucrose monoesters and more substituted esters at about a 5:1 ratio.
Sources: en.wikipedia.org
Conventional drying uses heat to evaporate water from a material, while lyophilization freezes the material and removes water by sublimation under vacuum. This avoids the liquid phase and reduces thermal damage to sensitive substances. The result is a porous cake that reconstitutes quickly.
A vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor without melting. It also removes water vapor from the product chamber and speeds up the drying process. Without vacuum, the ice would melt rather than sublimate.
Not all substances are suitable for lyophilization. Materials must form a stable frozen matrix and tolerate freezing and low pressure. Some small molecules, oils, or volatile compounds may not form a proper cake or may be lost during processing.
Conventional drying uses heat to evaporate liquid water, often at temperatures that can degrade sensitive materials. Lyophilization freezes the material first and then removes water by sublimation under vacuum. This avoids prolonged exposure to liquid water and high heat.