Anticholinergic Burden
📖 About
- 💊 Anticholinergic burden (ACB) refers to the cumulative effect of drugs with antimuscarinic activity. Older adults are especially vulnerable because of reduced cholinergic reserve, polypharmacy, and impaired renal clearance.
- 📉 High ACB has been linked with cognitive decline, delirium, dizziness, falls, urinary retention, constipation, and increased hospitalisation. Some evidence even suggests long-term use may contribute to dementia risk.
- ⚠️ In UK primary care, up to one-third of older adults are prescribed ≥1 drug with anticholinergic properties.
🩺 Clinical Features of Anticholinergic Toxicity
Remember the classic medical rhyme:
“Dry as a bone, blind as a bat, red as a beet, mad as a hatter, hot as a hare.” 🐇
This captures mucosal dryness, mydriasis, flushed skin, delirium, and fever from impaired sweating.
- 👄 Dry mouth, impaired swallowing, taste disturbance
- 🤢 Nausea, 💩 constipation, abdominal pain, paralytic ileus
- 🚽 Urinary hesitancy or retention - can precipitate acute kidney injury
- 👀 Blurred vision, photophobia, increased intraocular pressure
- ❤️ Tachycardia, palpitations
- 🧠 Neurological: agitation, confusion, hallucinations, delirium → seizures, coma
💊 Common Drug Classes with Anticholinergic Activity
- 📘 Tricyclic antidepressants - amitriptyline, imipramine
- 🌼 First-generation antihistamines - chlorpheniramine, diphenhydramine
- 🚻 Bladder antimuscarinics - oxybutynin, solifenacin, tolterodine
- 💉 Antipsychotics - chlorpromazine, haloperidol (weaker)
- 💊 Anti-Parkinson’s drugs - benzatropine, amantadine
🚫 Contraindications / High-Risk Conditions
- 👴 BPH – risk of urinary retention
- 👁️ Angle-closure glaucoma – can trigger acute crisis
- 💪 Myasthenia gravis – worsens neuromuscular weakness
- 🧠 Alzheimer’s / dementia – accelerates cognitive decline
- 🚫 Bowel obstruction or paralytic ileus
- 💧 Dehydrated/frail older adults – higher risk of delirium
📊 ACB Scoring Criteria
- 1️⃣ Score 1: In-vitro evidence of muscarinic antagonism, usually weak effect
- 2️⃣ Score 2: Clinical evidence or expert opinion of significant anticholinergic effects
- 3️⃣ Score 3: Strong evidence of causing delirium, high cognitive/functional risk
🔥 Examples of Score = 3 (Highest risk)
- Amitriptyline, Chlorpromazine
- Chlorpheniramine, Imipramine
- Solifenacin, Oxybutynin
⚠️ Examples of Score = 2
- Amantadine, Carbamazepine
ℹ️ Examples of Score = 1
- Aripiprazole, Atenolol, Cetirizine, Diazepam
- Digoxin, Dipyridamole, Disopyramide, Fentanyl
- Furosemide, Fluvoxamine, Haloperidol, Hydralazine
- Hydrocortisone, Isosorbide, Loperamide, Loratadine
- Metoprolol, Morphine, Nifedipine, Prednisone
- Quinidine, Ranitidine, Risperidone, Theophylline
- Trazodone, Triamterene, Venlafaxine, Warfarin
🧮 Practical Use
- 🧾 Use tools such as the Anticholinergic Cognitive Burden (ACB) scale in medication reviews.
- ⚖️ A total score ≥3 is associated with falls, hospitalisation and cognitive decline.
- 🔄 Always look for safer alternatives (e.g. SSRIs instead of TCAs for depression, second-generation antihistamines instead of sedating ones).
- 👨⚕️ Discuss deprescribing in MDT or GP medication reviews, especially in frail older adults.
💡 Teaching tip: Think about ACB whenever an older patient presents with new confusion or falls. The culprit is often hidden in a “harmless” drug like an antihistamine for hayfever or an oxybutynin patch for bladder urgency.
