Everything below concerns sublimation. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-09-23. Where a claim depends on a specific study, the study is described rather than over-claimed.
In practice, lyophilization is slower and more energy intensive than simple drying. Cycle times can range from hours to several days depending on load, container, and formulation. Amorphous materials may require excipients that help preserve structure during freezing and drying. The method is widely used for biological materials, pharmaceuticals, and foods where heat drying would cause unacceptable change. Open questions remain about scaling cycles between laboratory and production equipment, and this gap affects technology transfer.
Lyophilization removes water by freezing a material and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intermediate liquid state. Because the material remains frozen during primary drying, the structure often stays porous. This porous matrix can rehydrate quickly when water is added back. The low pressure also allows vapor to leave the solid matrix without boiling.
Stability programs monitor lyophilized products under defined temperature and humidity conditions over time. Real-time studies at recommended storage conditions are the reference, while accelerated studies provide early signals of degradation pathways. Because a dry cake can still undergo oxidation, hydrolysis, or aggregation, stability depends on residual moisture, excipients, and container headspace. Open questions include how best to predict long-term stability from short accelerated runs and how vial-to-vial variability affects shelf life. Current guidance treats these predictions as product-specific rather than universally generalizable.
Freeze-dried materials are hygroscopic to varying degrees and can take up moisture after drying. Storage therefore often uses sealed glass vials, rubber stoppers, and crimp seals to limit contact with ambient humidity. A desiccant may be included for moisture-sensitive products, although it is not universal. Controlled room temperature is sufficient for many lyophilizates, while others require refrigeration or freezing. Moisture ingress remains a primary cause of cake collapse, chemical degradation, and loss of reconstitution performance.
| Property | Value | Notes |
|---|---|---|
| Common synonym | Freeze-drying | Same dehydration operation |
| Typical vacuum | 10-100 Pa | Pressure during primary drying |
| Primary drying temperature | -40 to -10 °C | Below collapse temperature for many formulations |
| Cycle duration | 12-72 hours | Varies with load, container, and formulation |
| Key phase change | Sublimation | Solid ice to water vapor |
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.
Industries use lyophilization for pharmaceuticals, biological products, and food preservation. In the pharmaceutical sector, it extends the shelf life of injectable drugs, vaccines, and proteins that are unstable in aqueous solution. Food manufacturers apply freeze-drying to coffee, fruits, and ready meals to retain flavor and texture. The process is energy-intensive and requires specialized equipment, which limits its use to high-value products. Ongoing research examines how formulation and process parameters affect the quality of the final dried product.
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.
Handling practices aim to prevent moisture ingress and mechanical damage. Vials should remain stoppered and crimped until use, and reconstitution should follow the labeled diluent and volume. Shipping may involve temperature-controlled containers and desiccants, but direct contact between desiccant and product is avoided. Regulatory guidance expects documented storage conditions, excursion assessments, and stability commitments. Open questions remain about how best to predict long-term stability from short accelerated studies for every formulation class.
After lyophilization, the product is usually a porous cake or powder with a large internal surface area. This structure can absorb moisture quickly if exposed to humid air, so vials are sealed under vacuum or an inert gas. Moisture uptake may lower the glass transition temperature of the dried matrix and accelerate chemical or physical degradation. Storage conditions therefore depend on the formulation, container, and intended shelf life. Some products remain stable at room temperature, while others require refrigeration or freezing.
Equipment for lyophilization includes a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. A refrigeration system cools the shelves and condenser below the product's freezing point. Process monitoring often uses Pirani and capacitance manometers, thermocouples, and resistance sensors. Cycle development balances product quality with time and energy use. Some products are annealed during freezing to improve crystallization of bulking agents. Open questions remain about scaling cycles between laboratory, pilot, and production freeze-dryers.
Lyophilization, also called freeze-drying, removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts free water into ice and may also produce a glassy phase. Primary drying then lowers chamber pressure so ice sublimes directly to vapor without passing through a liquid stage. Secondary drying raises the temperature modestly to remove bound water. The result is a porous, dry solid that usually reconstitutes quickly. Each stage influences pore structure, residual moisture, and stability.
Quality control for freeze-dried forms includes visual inspection, water content measurement, and reconstitution time. A satisfactory cake is typically uniform, porous, and intact, although minor shrinkage or cracking may be acceptable if specifications allow. Karl Fischer titration, thermal gravimetric analysis, and near-infrared spectroscopy are used to measure water content. Reconstitution is assessed by adding a specified diluent and recording the time and ease of dissolution. Microbiological and particulate tests are added when the product is sterile or intended for injection.
Stability of a lyophilized solid depends on water content, temperature, and the physical state of the formulation. Amorphous products may slowly absorb moisture and drop below their glass transition temperature, causing collapse or crystallization. Some proteins and peptides can aggregate even in a dry state, especially when exposed to heat or moisture. Accelerated stability studies at elevated temperature and humidity help estimate shelf life, but real-time data remain the basis for expiration dating.
After drying, a lyophilized product is usually sealed under vacuum or an inert gas to limit moisture and oxygen exposure. The container closure system matters because stoppers and seals can allow moisture ingress over time. Storage conditions are selected from stability studies that track potency, cake appearance, and reconstitution behavior. Many freeze-dried materials are kept at controlled room temperature, while some require refrigeration or protection from light.
=== Occurrence of lactobacillic acid === Following the discovery of lactobacillic acid in the lipids of Lactobacillus arabinosus, Klaus Hofmann's team was also able to determine this fatty acid in the lipids of Lactobacillus casei with a content of 16%. It is also present in L. acidophilus, L. buchneri, L. delbrueckii subsp. bulgaricus, L. delbrueckii subsp. lactis, L. fermentum and L. helveticus with a content of 10 to 30% has been detected. However, lactobacillic acid is not restricted to members of the genus Lactobacillus or lactic acid bacteria in general. The fatty acid was also found in higher proportions (10-20%) in gram-negative bacteria, such as Agrobacterium tumefaciens and Escherichia coli detected, in smaller quantities (5-10%) also in Serratia marcescens, Klebsiella aerogenes and Pseudomonas fluorescens. Brucellaspecies also contain lactobacillic acid, as well as Bordetella species, but the content here is only 1-2%. Lactobacillic acid is found in both Gram-positive and Gram-negative bacteria and is found in strictly aerobic, microaerophilic, facultative and strictly anaerobic genera. genera. Although the fatty acid is widely distributed in bacteria, it is not found in all genera. Bacteria that do not have unsaturated fatty acids in their membrane lipids do not have lactobacillic acid. This applies in particular to thermophilic bacteria and archaea. However, the fatty acid is found rather rarely in eukaryotic organisms. It is contained, for example, in rapeseed oil, which contains little erucic acid (so-called LEAR varieties).
== Society and culture == A lack of recognition of diabulimia by clinicians leads to generally negative medical interactions. There is also a lack of public awareness. A lack of medical understanding creates social stigma. Because diabulimia tends not to involve significant eating restriction like anorexia nervosa, or purging as in bulimia nervosa, some do not recognise the significance of diabulimia. A BBC documentary in 2017 caused a significant increase in requests for specialist medical training for diabulimia, and improved public awareness.
Zinc deficiency may lead to loss of appetite. The use of zinc in the treatment of anorexia has been advocated since 1979. At least 15 clinical trials have shown that zinc improved weight gain in anorexia. A 1994 trial showed that zinc doubled the rate of body mass increase in the treatment of anorexia nervosa. Deficiency of other nutrients such as tyrosine, tryptophan and thiamine could contribute to this phenomenon of "malnutrition-induced malnutrition". A meta-analysis of 33 prospective intervention trials regarding zinc supplementation and its effects on the growth of children in many countries showed that zinc supplementation alone had a statistically significant effect on linear growth and body weight gain, indicating that other deficiencies that may have been present were not responsible for growth retardation.
Anti-Ro and anti-La antibodies, also known as SS-A and SS-B, respectively, are commonly found in primary Sjögren's syndrome, an autoimmune disorder that affects the exocrine glands. The presence of both antibodies is found in 30–60% of Sjögren's syndrome, anti-Ro antibodies alone are found in 50–70% of Sjögren's syndrome and 30% of SLE with cutaneous involvement, and anti-La antibodies are rarely found in isolation. Anti-La antibodies are also found in SLE; however, Sjögren's syndrome is normally also present. Anti-Ro antibodies are also found less frequently in other disorders including autoimmune liver diseases, coeliac disease, autoimmune rheumatic diseases, cardiac neonatal lupus erythematosus and polymyositis. During pregnancy, anti-Ro antibodies can cross the placenta and cause heart block and neonatal lupus in babies. In Sjögren's syndrome, anti-Ro and anti-La antibodies correlate with early onset, increased disease duration, parotid gland enlargement, disease outside the glands and infiltration of glands by lymphocytes. Anti-Ro antibodies are specific to components of the Ro-RNP complex, comprising 45kDa, 52kDa, 54kDa and 60kDa proteins and RNA. The 60kDa DNA/RNA binding protein and 52kDa T-cell regulatory protein are the best characterised antigens of anti-Ro antibodies. Collectively, these proteins are part of a ribonucleoprotein (RNP) complex that associate with the human Y RNAs, hY1-hY5. The La antigen is a 48kDa transcription termination factor of RNA polymerase III, which associates with the Ro-RNP complex.
As well as these common law standards, the Fair Work Act 2009 section 117 requires a bare minimum of 1 week's notice before 1 year, 2 weeks' notice for 2 years, 3 weeks' notice for over 3 years, and 4 weeks' notice for over 5 years, but also an extra week for employees over 45 years old who have worked more than 2 years. Modern awards can and often do have higher standards, and so do collective agreements. The dominant view is that courts may find greater notice is warranted where the facts speak in favour, because statute's purpose is to create a floor of rights, not a ceiling, that common law may improve upon, not undercut. An employer may give pay in lieu of notice under section 117(2) and terminate the contract if this has been accepted by the employee. The one situation where notice is not required is where a party commits a serious breach of contract. In these cases, an employee can quit on the spot and claim damages, or an employer can dismiss the employee. According to Bartlett v ANZ Banking Group Ltd a serious breach of the employment contract can include deliberate disobedience of a lawful and reasonable order, breaching the duty of fidelity (e.g. by taking secret commissions), or serious incompetence. In this case, an ANZ Bank employee won damages for wrongful dismissal on appeal, measured by 4 months notice that his contract required, since ANZ could not prove he had actually engaged in misconduct of sending confidential information to a journalist at the Australian Financial Review, and the employer had an obligation to act reasonably.
Sources: en.wikipedia.org
=== Guidelines === American Association of Blood Banks Clinical Practice Guidelines Australian National Blood Authority Patient Blood Management Guidelines British Committee for Standards in Haematology National Institute for Health and Care Excellence Blood Transfusion Guidance UK Guidance for transfusion. Canadian Blood Transfusion Guidelines German Medical Association Guidelines (English) Archived 2022-04-01 at the Wayback Machine, published 2014.
== Monitoring == It is important to recognize that all described exercise programs were conducted by physicians or physiotherapists during the stable phase of the disease (except Painelli). Patients were monitored closely for indicators of deleterious effects, such as increases in serum creatine kinase, inflammation or weakness. Monitoring of this kind can only be done in conjunction with a medical team that is aware of the risks posed by increased inflammatory response in patients with IIM.
1993/233) Non-Domestic Rates (Levying) (Scotland) Regulations 1993 (S.I. 1993/234) Poultry Meat (Hygiene) (Scotland) Amendment Regulations 1993 (S.I. 1993/235) Finance (No. 2) Act 1992, Schedule 9, (Appointed Day) Order 1993 (S.I. 1993/236) Criminal Justice Act 1988 (Application to Service Courts) (Evidence through Television Links) Order 1993 (S.I. 1993/244) Police (Promotion) (Scotland) Amendment Regulations 1993 (S.I. 1993/251) Non-Domestic Rating (Demand Notices) (Wales) Regulations 1993 (S.I. 1993/252) Council Tax (Transitional Reduction Scheme) (England) (Amendment) Regulations 1993 (S.I. 1993/253) Rules of the Air (Amendment) Regulations 1993 (S.I. 1993/254) Council Tax (Demand Notices) (Wales) Regulations 1993 (S.I. 1993/255) Valuation Timetable (Scotland) Amendment Order 1993 (S.I. 1993/256) Salmon (Definition of Methods of Net Fishing and Construction of Nets) (Scotland) Amendment Regulations 1993 (S.I. 1993/257) A417 Trunk Road (Brockworth Bypass and Slip Roads) Order 1993 (S.I. 1993/259) Social Security (Contributions) Amendment Regulations 1993 (S.I. 1993/260) A417 Trunk Road (Brockworth Bypass and Slip Roads) (Detrunking) Order 1993 (S.I. 1993/261) M5 Motorway (Brockworth Bypass and Slip Roads) (Slip Roads, Special Roads) Scheme 1993 (S.I. 1993/262) Industrial Training Levy (Construction Board) Order 1993 (S.I. 1993/265) Industrial Training Levy (Engineering Construction Board) Order 1993 (S.I. 1993/266) A4 Trunk Road (Reading Eastern Boundary to Maidenhead Thicket) Detrunking Order 1993 (S.I.
The reduction and subsequent reoxidation of vitamin K coupled with carboxylation of Glu is called the vitamin K cycle. Humans are rarely deficient in vitamin K because, in part, vitamin K2 is continuously recycled in cells. Warfarin and other 4-hydroxycoumarins block the action of VKOR. This results in decreased concentrations of vitamin K and vitamin K hydroquinone in tissues, such that the carboxylation reaction catalyzed by the glutamyl carboxylase is inefficient. This results in the production of clotting factors with inadequate Gla. Without Gla on the amino termini of these factors, they no longer bind stably to the blood vessel endothelium and cannot activate clotting to allow formation of a clot during tissue injury. As it is impossible to predict what dose of warfarin will give the desired degree of clotting suppression, warfarin treatment must be carefully monitored to avoid underdose and overdose.
Sources: en.wikipedia.org
Working with E. R. Giblett in 1972, Ammann described the first patient with purine nucleoside phosphorylase deficiency in association with a unique genetic profile that included depressed T-cell immunity with normal levels of immunoglobulins. The resulting publication was listed as one of the 500 most widely cited articles in 1984. Ammann's discovery represented an essential step to understanding new treatments for immunodeficiency diseases and developing drugs that could interfere with the immune response.
=== United States === The Orphan Drug Act (ODA) of January 1983, passed in the United States, with lobbying from the National Organization for Rare Disorders and many other organizations, is meant to encourage pharmaceutical companies to develop drugs for diseases that have a small market. Under the ODA drugs, vaccines, and diagnostic agents would qualify for orphan status if they were intended to treat a disease affecting fewer than 200,000 American citizens. Under the ODA orphan drug sponsors qualify for seven-year FDA-administered market Orphan Drug Exclusivity (ODE), "tax credits of up to 50% of R&D costs, R&D grants, waived FDA fees, protocol assistance and may get clinical trial tax incentives. In the U.S., orphan drug designation means that the sponsor qualifies for certain benefits, but it does not mean the drug is safe, effective or legal. In 2002, the Rare Diseases Act was signed into law. It amended the Public Health Service Act to establish the Office of Rare Diseases. It also increased funding for the development of treatments for people with rare diseases.
=== Intravenous === Vancomycin must be given intravenously for systemic therapy since it is poorly absorbed from the intestine. Vancomycin is a large hydrophilic molecule that partitions poorly across the gastrointestinal mucosa. Due to its short half-life, it is often injected twice daily.
== Types == Popliteal pterygium syndrome, a congenital condition affecting the face, limbs, or genitalia but named after the wing-like structural anomaly behind the knee. Pterygium (eye) or surfer's eye, a growth on the cornea of the eye. Pterygium colli or webbed neck, a congenital skin fold of the neck down to the shoulders. Pterygium inversum unguis or ventral pterygium, adherence of the distal portion of the nailbed to the ventral surface of the nail plate. Pterygium unguis or dorsal pterygium, scarring between the proximal nail fold and matrix.
== Physiology == Fibrosis is similar to the process of scarring, in that both involve stimulated fibroblasts laying down connective tissue, including collagen and glycosaminoglycans. The process is initiated when immune cells such as macrophages release soluble factors that stimulate fibroblasts. The most well characterized pro-fibrotic mediator is TGF beta, which is released by macrophages as well as any damaged tissue between surfaces called interstitium. Other soluble mediators of fibrosis include CTGF, platelet-derived growth factor (PDGF), and interleukin 10 (IL-10). These initiate signal transduction pathways such as the AKT/mTOR and SMAD pathways that ultimately lead to the proliferation and activation of fibroblasts, which deposit extracellular matrix into the surrounding connective tissue. This process of tissue repair is a complex one, with tight regulation of extracellular matrix (ECM) synthesis and degradation ensuring maintenance of normal tissue architecture. However, the entire process, although necessary, can lead to a progressive irreversible fibrotic response if tissue injury is severe or repetitive, or if the wound healing response itself becomes deregulated.
Sources: en.wikipedia.org
Primary drying removes ice by sublimation under vacuum. Secondary drying removes water that is bound to the material, often by warming the product after most ice has left. Both stages occur below temperatures that would cause unwanted melting.
Sublimation requires the solvent to remain solid so vapor leaves without passing through a liquid phase. If the product melts, the porous structure can collapse and drying becomes uneven. Maintaining frozen conditions preserves the intended physical form.
No, freeze-drying is a dehydration method, not a sterilization step. It can reduce water activity and limit microbial growth during storage, but it does not reliably kill microbes or remove endotoxins. Sterility must come from separate validated processes.
Many dried cakes are hygroscopic and can adsorb water during storage or handling. Absorbed moisture may lower the glass transition temperature and promote chemical reactions. Sealed packaging and controlled humidity reduce this risk.