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In pharmaceutical manufacturing, the active ingredient (API) is the most valuable and delicate element. Drying is the last step before storage: a mistake at this stage can nullify all the previous work, altering the purity or structure of the drug. Choosing the right drying technology, therefore, is not a simple technical matter, but a strategic choice to ensure an effective product, compliance with health laws and the protection of those who work in the plant.
What are APIs and why drying is a critical step
An API is the biologically active substance that produces the therapeutic effect in a medicine. According to ICH Q7, APIs are defined as any substance used in the production of a medicine that becomes an active part of it. For this reason, the entire production cycle — including the critical vacuum drying steps — must strictly comply with GMP standards to ensure quality and safety.
Drying typically takes place downstream of filtration: the product looks like a wet paste containing residual organic solvents — acetone, ethanol, isopropanol, DMF, among the most common. The goal is to bring the content of moisture and residual solvents below the regulatory limits, while preserving all the chemical-physical properties that determine the quality of the active ingredient: purity, polymorphism, particle size, solubility.
An error at this stage has consequences that can no longer be corrected: thermal degradation of a molecule, undesirable polymorphic transition or exceeding ICH limits for residual solvents result in the rejection of the entire batch.
Compared to other industrial products, APIs have a combination of critical issues that make conventional drying with hot air often inadequate or directly inapplicable.
Many pharmaceutical molecules are heat unstable: temperatures above 40–60 °C can initiate degradation reactions that generate impurities not specified in the registration dossier. The ICH Q3A and Q3B guidelines impose very strict limits on degradation impurities, with qualification thresholds often less than 0.1% compared to the substance. Conventional air drying at 80–120 °C leaves little margin of safety for these molecules.
Residual solvents and ICH Q3C compliance
The ICH Q3C guideline classifies solvents into three classes based on toxicity: Class 1 solvents (benzene, chloroform) should be avoided or reduced to levels of a few ppm; Class 2 (methanol, DMF, acetonitrile) have acceptable daily limits expressed in mg/day; Class 3 solvents (ethanol, acetone, PAHs) are the least restrictive but still require documentation and control. The drying process must ensure documented and reproducible removal of solvents within these limits, batch by batch.
Dison reference
ICH Q3C (R8) — Impurities: Guideline for Residual Solvents. The guideline defines permissible daily exposure limits (PDEs) for more than 60 solvents and requires the manufacturer to demonstrate, through validation studies, that the drying process reproducibly achieves the removal targets.
Many APIs have different crystalline forms (polymorphisms) that affect their solubility and effectiveness. If drying conditions — such as temperature and evaporation rate — are not controlled, they can cause unwanted structural changes. This would force the company to repeat laboratory tests and update the documents filed with the health authorities, with a considerable expenditure of time and costs. Millimetric control of pressure and temperature is therefore essential to ensure the stability of the correct crystalline shape.
A growing category of APIs — Highly Potent APIs (HPAPIs), including beta-lactam, hormone, cytotoxic, and oncological antibiotics — require containment measures to protect the operator from exposure. The OEL (Occupational Exposure Limit) for these molecules often falls below 10 μg/m³ (OEB 4) or even below 1 μg/m³ (OEB 5). In these contexts, the drying system must guarantee bidirectional containment: the product must not contaminate the environment, and the environment must not contaminate the product.
Vacuum drying acts on the most accessible parameter of process thermodynamics: pressure. By lowering the pressure in the drying chamber, the boiling temperature of the solvent is proportionately reduced. For water, at 50 mbar the boiling point drops to about 33 °C; at 10 mbar at about 7 °C. This principle applies to all organic solvents common in pharmaceutical manufacturing, allowing their removal at temperatures that do not compromise the molecular integrity of the active ingredient.
Protection
The solvent evaporates at ambient temperatures, eliminating the risk of thermal degradation. The operating delta compared to conventional drying is typically 70–80 °C.
Absence of oxygen
The closed and vacuum system excludes air, protecting oxidizable molecules and eliminating the risk of explosive atmospheres in the presence of flammable solvents (ATEX compliance).
Bi-directional containment
The closed system prevents both contamination of the product by external sources and operator exposure to the active ingredient — essential for HPAPIs.
Solvent Recovery
The extracted steam is condensed and collected in pure liquid form, which is reusable in the process. VOC emissions are virtually zero, with a direct impact on environmental compliance.
For further reading: Vacuum drying technology: physical principles and advantages
The quality of an API does not depend only on its chemical purity. Factors such as crystal shape, granule size, residual moisture and the ability of the powder to flow easily (flowability) are critical features. These properties affect both the effectiveness of the drug and the ease with which the powder is processed to create tablets or capsules.
Vacuum drying allows these attributes to be controlled with the accuracy that conventional drying would not allow. The low process temperature reduces the risk of thermally induced polymorphic transitions. The ability to precisely modulate the pressure profile during the cycle — applying gradual ramps rather than a high vacuum from the start — allows you to guide the removal of the solvent in a way that preserves the desired crystal structure.
Residual moisture, measured using specific techniques such as Karl Fischer titration or heat weight loss (TGA), is a key value to be declared to health authorities. During the testing of the machinery, the drying system must demonstrate that it can always achieve the same level of dryness required, guaranteeing constant and safe results for each production batch.
Regulatory compliance and process documentation
The production of APIs is regulated internationally by the ICH Q7 guideline, implemented by the FDA, EMA and the regulatory authorities of over 50 countries. ICH Q7 dedicates a specific chapter to drying and requires critical process parameters to be identified, monitored and documented for each batch.
Framework reference legislation
ICH Q7 (GMP for Active Pharmaceutical Ingredients) — defines GMP requirements for the production of APIs, including drying operations. ICH Q8, Q9 and Q10 — guidelines on Pharmaceutical Development, Quality Risk Management and Pharmaceutical Quality System, which together define the Quality by Design (QbD) framework applicable to the validation of drying processes.
The modern regulatory approach is oriented towards Process Analytical Technology (PAT), i.e., the continuous monitoring of the process during the production cycle, rather than the simple control at the end of the batch. In vacuum drying, parameters such as chamber pressure and condenser temperature are measurable in real time, making the process ideal for PAT systems.
A state-of-the-art system — such as those designed by Italvacuum — is not just a machine, but a process intelligence: it is a source of structured data for the documentation of the batch record, for the demonstration of reproducibility and for the support of ministerial inspection activities.
Italvacuum designs vacuum drying systems engineered for the specific needs of API production. The technologies adopted guarantee the integrity of the thermolabile products and the total containment of the substances, integrating in-line control systems according to the PAT (Process Analytical Technology) approach. This allows critical parameters to be monitored in real time, ensuring full compliance with GMP regulations and automatic and accurate documentation of each batch.
For APIs that require gentle agitation and precise control of the drying temperature, the Planex® System — horizontal vacuum dryer with a paddle agitator with two independent movements — is the go-to solution. The heated agitator constantly renews the exposed surface of the product, accelerating the phase at decreasing speed of the cycle without mechanically stressing the crystal. The geometry of the movement reduces the formation of hot spots and ensures uniformity of treatment throughout the volume of the bed.
For HPAPIs and applications that require high-containment loading and unloading systems, Italvacuum has integrated solutions designed to achieve the containment levels required by the most restrictive OEBs.
Before any investment in a new drying plant, Italvacuum makes its pilot plants available to customers for semi-industrial and laboratory drying tests. Pilot tests allow the collection of process data — drying curves, temperature and pressure profiles, solvent recovery yields — which form the basis for the selection of the most suitable technology and for the development and validation of the process on an industrial scale.
Do you have an API drying process to develop or optimize?
Italvacuum's technical team is available for an analysis of your process and to evaluate the most suitable solution together.
CONTACT US
What are APIs and why drying is a critical step
An API is the biologically active substance that produces the therapeutic effect in a medicine. According to ICH Q7, APIs are defined as any substance used in the production of a medicine that becomes an active part of it. For this reason, the entire production cycle — including the critical vacuum drying steps — must strictly comply with GMP standards to ensure quality and safety.
Drying typically takes place downstream of filtration: the product looks like a wet paste containing residual organic solvents — acetone, ethanol, isopropanol, DMF, among the most common. The goal is to bring the content of moisture and residual solvents below the regulatory limits, while preserving all the chemical-physical properties that determine the quality of the active ingredient: purity, polymorphism, particle size, solubility.
An error at this stage has consequences that can no longer be corrected: thermal degradation of a molecule, undesirable polymorphic transition or exceeding ICH limits for residual solvents result in the rejection of the entire batch.
The specific needs of APIs in the drying process
Compared to other industrial products, APIs have a combination of critical issues that make conventional drying with hot air often inadequate or directly inapplicable.
Thermosensitivity and risk of degradation
Many pharmaceutical molecules are heat unstable: temperatures above 40–60 °C can initiate degradation reactions that generate impurities not specified in the registration dossier. The ICH Q3A and Q3B guidelines impose very strict limits on degradation impurities, with qualification thresholds often less than 0.1% compared to the substance. Conventional air drying at 80–120 °C leaves little margin of safety for these molecules.
Residual solvents and ICH Q3C compliance
The ICH Q3C guideline classifies solvents into three classes based on toxicity: Class 1 solvents (benzene, chloroform) should be avoided or reduced to levels of a few ppm; Class 2 (methanol, DMF, acetonitrile) have acceptable daily limits expressed in mg/day; Class 3 solvents (ethanol, acetone, PAHs) are the least restrictive but still require documentation and control. The drying process must ensure documented and reproducible removal of solvents within these limits, batch by batch.
Dison reference
ICH Q3C (R8) — Impurities: Guideline for Residual Solvents. The guideline defines permissible daily exposure limits (PDEs) for more than 60 solvents and requires the manufacturer to demonstrate, through validation studies, that the drying process reproducibly achieves the removal targets.
Polymorphism and morphology of the crystal
Many APIs have different crystalline forms (polymorphisms) that affect their solubility and effectiveness. If drying conditions — such as temperature and evaporation rate — are not controlled, they can cause unwanted structural changes. This would force the company to repeat laboratory tests and update the documents filed with the health authorities, with a considerable expenditure of time and costs. Millimetric control of pressure and temperature is therefore essential to ensure the stability of the correct crystalline shape.
Containment for HPAPIs
A growing category of APIs — Highly Potent APIs (HPAPIs), including beta-lactam, hormone, cytotoxic, and oncological antibiotics — require containment measures to protect the operator from exposure. The OEL (Occupational Exposure Limit) for these molecules often falls below 10 μg/m³ (OEB 4) or even below 1 μg/m³ (OEB 5). In these contexts, the drying system must guarantee bidirectional containment: the product must not contaminate the environment, and the environment must not contaminate the product.
Why vacuum is the technical answer to API needs
Vacuum drying acts on the most accessible parameter of process thermodynamics: pressure. By lowering the pressure in the drying chamber, the boiling temperature of the solvent is proportionately reduced. For water, at 50 mbar the boiling point drops to about 33 °C; at 10 mbar at about 7 °C. This principle applies to all organic solvents common in pharmaceutical manufacturing, allowing their removal at temperatures that do not compromise the molecular integrity of the active ingredient.
Advantages of vacuum drying thermal
Protection
The solvent evaporates at ambient temperatures, eliminating the risk of thermal degradation. The operating delta compared to conventional drying is typically 70–80 °C.
Absence of oxygen
The closed and vacuum system excludes air, protecting oxidizable molecules and eliminating the risk of explosive atmospheres in the presence of flammable solvents (ATEX compliance).
Bi-directional containment
The closed system prevents both contamination of the product by external sources and operator exposure to the active ingredient — essential for HPAPIs.
Solvent Recovery
The extracted steam is condensed and collected in pure liquid form, which is reusable in the process. VOC emissions are virtually zero, with a direct impact on environmental compliance.
For further reading: Vacuum drying technology: physical principles and advantages
Impact on the quality of the final product
The quality of an API does not depend only on its chemical purity. Factors such as crystal shape, granule size, residual moisture and the ability of the powder to flow easily (flowability) are critical features. These properties affect both the effectiveness of the drug and the ease with which the powder is processed to create tablets or capsules.
Vacuum drying allows these attributes to be controlled with the accuracy that conventional drying would not allow. The low process temperature reduces the risk of thermally induced polymorphic transitions. The ability to precisely modulate the pressure profile during the cycle — applying gradual ramps rather than a high vacuum from the start — allows you to guide the removal of the solvent in a way that preserves the desired crystal structure.
Residual moisture, measured using specific techniques such as Karl Fischer titration or heat weight loss (TGA), is a key value to be declared to health authorities. During the testing of the machinery, the drying system must demonstrate that it can always achieve the same level of dryness required, guaranteeing constant and safe results for each production batch.
Regulatory compliance and process documentation
The production of APIs is regulated internationally by the ICH Q7 guideline, implemented by the FDA, EMA and the regulatory authorities of over 50 countries. ICH Q7 dedicates a specific chapter to drying and requires critical process parameters to be identified, monitored and documented for each batch.
Framework reference legislation
ICH Q7 (GMP for Active Pharmaceutical Ingredients) — defines GMP requirements for the production of APIs, including drying operations. ICH Q8, Q9 and Q10 — guidelines on Pharmaceutical Development, Quality Risk Management and Pharmaceutical Quality System, which together define the Quality by Design (QbD) framework applicable to the validation of drying processes.
The modern regulatory approach is oriented towards Process Analytical Technology (PAT), i.e., the continuous monitoring of the process during the production cycle, rather than the simple control at the end of the batch. In vacuum drying, parameters such as chamber pressure and condenser temperature are measurable in real time, making the process ideal for PAT systems.
A state-of-the-art system — such as those designed by Italvacuum — is not just a machine, but a process intelligence: it is a source of structured data for the documentation of the batch record, for the demonstration of reproducibility and for the support of ministerial inspection activities.
The Italvacuum solution for API production
Italvacuum designs vacuum drying systems engineered for the specific needs of API production. The technologies adopted guarantee the integrity of the thermolabile products and the total containment of the substances, integrating in-line control systems according to the PAT (Process Analytical Technology) approach. This allows critical parameters to be monitored in real time, ensuring full compliance with GMP regulations and automatic and accurate documentation of each batch.
For APIs that require gentle agitation and precise control of the drying temperature, the Planex® System — horizontal vacuum dryer with a paddle agitator with two independent movements — is the go-to solution. The heated agitator constantly renews the exposed surface of the product, accelerating the phase at decreasing speed of the cycle without mechanically stressing the crystal. The geometry of the movement reduces the formation of hot spots and ensures uniformity of treatment throughout the volume of the bed.
For HPAPIs and applications that require high-containment loading and unloading systems, Italvacuum has integrated solutions designed to achieve the containment levels required by the most restrictive OEBs.
Before any investment in a new drying plant, Italvacuum makes its pilot plants available to customers for semi-industrial and laboratory drying tests. Pilot tests allow the collection of process data — drying curves, temperature and pressure profiles, solvent recovery yields — which form the basis for the selection of the most suitable technology and for the development and validation of the process on an industrial scale.
Do you have an API drying process to develop or optimize?
Italvacuum's technical team is available for an analysis of your process and to evaluate the most suitable solution together.
CONTACT US