ACB Score: Sum of anticholinergic drug scores. Total ≥ 3 = clinically significant cumulative burden.
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Medication review in adults ≥65 at risk of cognitive impairment or falls.
Preoperative polypharmacy assessment in older surgical patients.
Evaluating possible drug-induced delirium or unexplained cognitive decline.
Pharmacy-led deprescribing initiatives in nursing home and primary care settings.
Why Anticholinergics Matter in Older Adults
Anticholinergic drugs block muscarinic receptors in the brain and periphery. In older adults, age-related reductions in acetylcholine production and blood-brain barrier integrity dramatically increase susceptibility to cognitive side effects — even at doses tolerated in younger patients.
Section 2
Formula & Logic
ACB Scoring System
Each medication assigned 1, 2, or 3 based on anticholinergic potency
Score 1: Possible anticholinergic activity (in vitro evidence only)
Score 2: Moderate anticholinergic activity (adverse effects in some patients)
Score 3: Definite anticholinergic activity (clinically significant effects)
Total ACB = sum of scores across all current medications
Total ACB ≥ 3 = clinically significant cumulative anticholinergic burden
High-Burden Drug Examples (Score 3)
| Amitriptyline | TCA antidepressant — avoid in older adults |
| Oxybutynin | Urinary anticholinergic — significant CNS penetration |
| Diphenhydramine | Antihistamine — frequently misused for sleep |
| Chlorphenamine | OTC antihistamine — high CNS anticholinergic effect |
| Promethazine | Antiemetic/antihistamine — strong CNS penetration |
| Hyoscine (Scopolamine) | High anticholinergic burden across all routes |
Section 3
Pearls/Pitfalls
ACB vs. Other Anticholinergic Tools
Multiple anticholinergic burden tools exist (ACB, ADS, DBI). The ACB scale is among the best validated for cognitive outcomes. Unlike the Drug Burden Index (DBI), it focuses specifically on anticholinergic load rather than combined sedative + anticholinergic exposure.
Clinical Consequences of High ACB
Acute delirium — especially in hospitalised or post-surgical older adults.
Accelerated long-term cognitive decline and increased dementia risk.
Falls and fractures due to sedation and impaired balance.
Constipation, urinary retention, dry mouth, blurred vision (peripheral effects).
Increased all-cause mortality in long-term care populations.
Section 4
Next Steps
Deprescribing Strategy by ACB
| ACB 0–2 | Low burden — no immediate action; maintain awareness. |
| ACB 3–5 | Moderate burden — identify highest-ACB drugs; seek safer alternatives (e.g., SNRI over TCA; solifenacin/mirabegron over oxybutynin). |
| ACB ≥ 6 | High burden — prioritise systematic deprescribing; involve pharmacist; consider specialist referral. |
Safer Alternatives to Consider
Replace oxybutynin with mirabegron (beta-3 agonist) for overactive bladder.
Replace diphenhydramine with melatonin or CBT-I for insomnia.
Replace TCAs with SSRIs/SNRIs for depression.
Replace first-generation antihistamines with loratadine or cetirizine (lower CNS penetration).
Section 5
Evidence Appraisal
Primary Reference
The anticholinergic risk scale and anticholinergic adverse effects in older persons.
Rudolph JL et al. • Arch Intern Med.. 2008;168(5):508–513. Derivation of the ACB scale with prospective validation in 132 older veterans.
Anticholinergic effect on cognition (AEC) of drugs commonly used in older people.
Bishara D et al. • Int J Geriatr Psychiatry.. 2017;32(6):650–656. Validation study correlating ACB with cognitive outcomes in 110 inpatients.
Section 6
Origins
Background
The Anticholinergic Burden Score emerged from the recognition that older patients frequently receive multiple drugs with individual anticholinergic properties that are individually tolerable but collectively produce significant cognitive toxicity. The concept of cumulative anticholinergic burden — the summation of individual drug scores — was formalised to enable systematic medication review and deprescribing in geriatric populations.
Last Comprehensive Review: 2026