Anticholinergic medications are a diverse group of drugs that work by blocking the action of acetylcholine, a neurotransmitter that plays a crucial role in communication between nerve cells. Acetylcholine is involved in a wide range of bodily functions, including muscle contraction, heart rate regulation, and memory. While many drugs are intentionally designed as anticholinergics to treat specific conditions like overactive bladder or asthma, many others have anticholinergic effects as an unintended side effect. The resulting anticholinergic experience can manifest differently based on the dose, the individual's sensitivity, and whether the effects are peripheral (physical) or central (mental).
The Physical Experience: Peripheral Anticholinergic Effects
The physical sensations of anticholinergic effects are often described using a classic medical mnemonic: "Dry as a bone, blind as a bat, hot as a hare, red as a beet, and full as a flask". These symptoms directly result from the blockade of acetylcholine in the peripheral nervous system, which controls involuntary body functions.
- Dry Mouth (Dry as a bone): One of the most common and bothersome effects is a significant reduction in saliva production. This can lead to difficulty swallowing, oral health issues like cavities and infections, and an overall dry, uncomfortable feeling in the mouth.
- Blurred Vision (Blind as a bat): Anticholinergics dilate the pupils and affect the eye muscles responsible for focusing, leading to blurry near vision and increased sensitivity to light (photophobia). For individuals with a pre-existing condition like narrow-angle glaucoma, this effect can be dangerous by increasing intraocular pressure.
- Constipation (Bloated as a toad/Dry as a bone): Acetylcholine stimulates the smooth muscles of the digestive tract. By blocking this, anticholinergics slow down bowel movements, leading to constipation and, in severe cases, a complete lack of bowel sounds.
- Urinary Retention (Full as a flask): These drugs relax the bladder muscles, making it difficult to fully empty the bladder, which can cause urinary retention. This is particularly risky for individuals with an enlarged prostate.
- Decreased Sweating (Hot as a hare): The suppression of sweat gland activity can cause a person to feel overheated and flushed. In severe situations, especially during exercise or in hot weather, this can lead to dangerous heat exhaustion or heat stroke.
- Rapid Heart Rate (Tachycardia): Anticholinergics can interfere with the body's heart rate regulation, resulting in a faster-than-usual heartbeat or the feeling that one's heart is pounding or racing.
The Mental Experience: Central Nervous System Effects
When anticholinergic medications cross the blood-brain barrier, they can affect the central nervous system, leading to a range of cognitive and psychiatric symptoms. Older adults are particularly susceptible due to age-related changes in brain chemistry and drug metabolism.
Confusion, Drowsiness, and Memory Problems
At lower doses, central effects can feel like a persistent brain fog, characterized by difficulty concentrating, memory lapses, and general mental confusion. People may also experience significant drowsiness and sedation. These symptoms are often mistaken for normal aging, but they are a direct effect of the medication.
Delirium and Hallucinations
At higher doses or in susceptible individuals, central anticholinergic effects can escalate to a state of agitated delirium, described by the mnemonic phrase "mad as a hatter". This medical emergency involves severe confusion, restlessness, and an altered mental state. Hallucinations, often visual, can occur, sometimes described as "lilliputian" (seeing small people or objects). People may feel anxious, irritable, and paranoid during this state.
Anticholinergic Burden and Long-Term Risks
Taking multiple medications with anticholinergic properties, a phenomenon known as anticholinergic burden, increases the risk and severity of these side effects. In recent years, research has also suggested a link between long-term use of anticholinergic medications and an increased risk of dementia, particularly Alzheimer's disease. This link is especially relevant for older people, whose brains are already experiencing age-related decreases in acetylcholine.
Comparison of Peripheral vs. Central Anticholinergic Effects
| Symptom Category | Peripheral Effects (Physical) | Central Effects (Mental/Cognitive) |
|---|---|---|
| Bodily Secretions | Dry mouth, decreased sweating, dry eyes | Not directly affected (primary CNS function) |
| Vision | Blurred vision, dilated pupils, light sensitivity | Hallucinations, altered perception |
| Gastrointestinal | Constipation, slowed digestion | Not directly affected (primary CNS function) |
| Urinary | Urinary retention, difficulty urinating | Not directly affected (primary CNS function) |
| Cardiovascular | Rapid heart rate (tachycardia) | Not directly affected (primary CNS function) |
| Mental State | Not directly affected (primary PNS function) | Confusion, memory loss, drowsiness, delirium |
| Behavior | Reduced physical coordination | Agitation, restlessness, irritability |
Seeking Help for Anticholinergic Effects
If you believe you are experiencing anticholinergic side effects, it is crucial to speak with a healthcare provider. Do not abruptly stop taking any prescribed medication. Your doctor may need to adjust the dosage, switch to an alternative medication with less anticholinergic activity, or address your overall anticholinergic burden. For signs of severe anticholinergic toxicity, such as delirium or seizures, seek immediate medical attention.
Conclusion: A Multi-System Impact
For those asking "what does anticholinergic feel like?", the answer is a complex combination of physical and mental symptoms that stem from the blocking of a vital neurotransmitter, acetylcholine. The experience can range from mildly inconvenient physical dryness and blurred vision to severe cognitive impairment and delirium. Being aware of these potential effects, especially for older adults or those on multiple medications, is a critical step in managing health and mitigating potential risks associated with anticholinergic drug use.
For more in-depth information on managing anticholinergic drug use and its potential risks, particularly in older adults, Harvard Health provides extensive resources. Link to Harvard Health article: Common anticholinergic drugs like Benadryl linked to increased dementia risk.
