Physiological substrates and membranes

Physiological substrates and membranes refers to a pharmacological classification for drugs that do not interact with specific protein receptors, enzymes, or transporters (Britannica, 2024). Instead, these agents exert their therapeutic effects through direct physical or chemical interactions with non-proteinaceous components of the body. For example, antacids like aluminum hydroxide work by chemically neutralizing hydrochloric acid in the stomach to relieve dyspepsia (StatPearls, 2023). Osmotic agents, such as mannitol, create concentration gradients that shift water across biological membranes, which is useful in treating cerebral edema or constipation (NIH, 2022). Other drugs in this category, including certain general anesthetics and surfactants, act by altering the physical properties, fluidity, or surface tension of lipid bilayers (PubMed, 2021). Bile acid sequestrants and activated charcoal function through physical adsorption, binding to lipids or toxins within the gastrointestinal tract to prevent their absorption (DrugBank Online). Because these mechanisms are often non-specific, these drugs typically require higher dosages than protein-targeted therapies and do not follow traditional lock-and-key kinetics. While effective for symptomatic relief, targeting these substrates can lead to challenges such as systemic electrolyte imbalances or the unintended malabsorption of other medications.

Other names

Non-specific targetsBiological membranesPhysiological substratesNon-protein targetsChemical targetsNon-receptor targets

Chemical neutralization, osmotic gradient modulation, physical adsorption, and membrane fluidization.