Older adult risk classification for anticholinergics (ORCA): a Delphi panel-validated scale

Background: Drugs with anticholinergic properties (DAP) are widely prescribed in older adults for various medical conditions. However, their cumulative anticholinergic burden is associated with adverse outcomes, including cognitive decline, falls and hospitalisations. Anticholinergic scales vary significantly, complicating their interpretation and application into clinical practice and research. Recent systematic reviews provide an overview of existing scales, however often lack the clinical perspective of healthcare professionals. To address this gap, we developed the older adult risk classification for anticholinergics (ORCA) scale, incorporating both evidence and expert clinical judgement. Methods: A preliminary drug list was derived from the most comprehensive systematic review. A two-round Delphi process was conducted with 14 clinicians from nine European countries with substantial expertise in geriatric medicines and clinical pharmacology. Each round consisted of two phases in which experts rated the anticholinergic burden of drugs using a four-point Likert scale. Additional drugs and anticholinergic burden scales could be proposed at any point. Consensus was defined using the Lynn method. Results: A total of 233 drugs were assessed. Experts classified 17 drugs as having no anticholinergic properties, 115 as low, 31 as moderate and 65 as high burden. The majority of included DAP were central nervous system drugs, particularly antipsychotics and antidepressants. Five drugs did not reach consensus. Conclusion: The ORCA scale is a clinically informed, evidence-based classification of DAP tailored for older adults. It offers a standardised tool to support clinicians, pharmacists and researchers in assessing anticholinergic burden, enhancing prescribing safety and guiding therapeutic decision-making in this vulnerable population.