Adsorption – Medical Meaning and Applications
Adsorption is the process by which substances adhere to the surface of a material. In medicine, it is used to bind toxins or harmful substances in the body and prevent their absorption.
Things worth knowing about "Adsorption"
Adsorption is the process by which substances adhere to the surface of a material. In medicine, it is used to bind toxins or harmful substances in the body and prevent their absorption.
What is Adsorption?
Adsorption is a physicochemical process in which molecules, ions, or particles from a gas or liquid adhere to the surface of a solid material, known as the adsorbent. Unlike absorption, where substances penetrate into a material, adsorption occurs exclusively at the surface. In medicine and pharmacy, this process plays an important role in detoxification, drug formulation, and medical filtration procedures.
Basic Principle of Adsorption
During adsorption, substances are held to a surface by either physical forces (Van der Waals forces) or chemical bonds. Two main types are distinguished:
- Physisorption: Weak, reversible binding through Van der Waals forces. The adsorbed substance can be easily released again.
- Chemisorption: Stronger, often irreversible binding through chemical reactions between the adsorbate and the surface of the adsorbent.
The efficiency of adsorption is strongly dependent on the surface area of the adsorbent. Materials with a very large internal surface area, such as activated charcoal, are particularly effective adsorbents.
Medical Applications
Activated Charcoal in Poisoning
One of the most well-known medical applications of adsorption is the use of activated charcoal (medical term: Carbo medicinalis) in acute poisoning cases. Activated charcoal has an extremely large surface area and can bind a wide variety of toxins, medications, and other harmful substances in the gastrointestinal tract, preventing their absorption into the bloodstream. It is typically administered as a suspension and is most effective when given within the first hour after poisoning.
Hemodialysis and Hemoperfusion
In nephrology and intensive care medicine, adsorption principles are used in hemoperfusion. In this procedure, the blood of the patient is passed over an adsorbent material (e.g., activated charcoal or special synthetic resins) to remove toxins, drugs, or other harmful substances directly from the blood. This technique complements or replaces hemodialysis in certain clinical situations.
Pharmaceutical Formulation
In pharmacology, adsorption is deliberately used to bind active ingredients to carrier materials. This can control the release rate of a drug (so-called sustained-release formulations) or improve the stability and bioavailability of an active substance. Vaccines also make use of adsorption, for example through aluminum salts used as adjuvants that bind antigens to their surface and thereby enhance the immune response.
Water Treatment and Medical Technology
In medical infrastructure, adsorption is applied in water purification and in the cleaning of medical gases. Filter systems in dialysis machines, ventilators, and sterile clean rooms use adsorption materials to remove contaminants and ensure patient safety.
Relevant Adsorbents in Medicine
- Activated charcoal: Broad-spectrum adsorbent used in poisoning and drug overdose
- Aluminum hydroxide / aluminum phosphate: Adjuvants in vaccines that bind antigens and boost the immune response
- Zeolites and synthetic resins: Used in hemoperfusion and dialysis procedures
- Smectite (diosmectite): A natural clay mineral used as an intestinal adsorbent in diarrheal diseases to bind pathogens and toxins
Limitations and Risks
Although adsorption is widely useful in medicine, it also has limitations. Not all substances are adsorbed equally well. For example, alcohols, iron salts, and certain acids are poorly bound by activated charcoal. Furthermore, an adsorbent may simultaneously bind beneficial substances such as medications or nutrients alongside harmful ones, which must be taken into account during treatment. In hemoperfusion, blood cells and proteins can also be non-specifically adsorbed, which may cause side effects.
References
- Katzung, B.G., Masters, S.B., Trevor, A.J. - Basic and Clinical Pharmacology. McGraw-Hill Education, 14th edition (2018).
- WHO - Poisoning Prevention and Management: Activated Charcoal Use. World Health Organization, Geneva (2020). Available at: https://www.who.int
- Brunton, L.L., Hilal-Dandan, R., Knollmann, B.C. - Goodman & Gilman's The Pharmacological Basis of Therapeutics. McGraw-Hill, 13th edition (2018).
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