Cholinergic Pharmacology

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Last updated: May 23, 2026Bookmark

Table Of Contents

Overview
Cholinergics (Cholinomimetics)
Anticholinergics (Parasympatholytics)

Overview

Acetylcholine (Ach)is the main neurotransmitter of the parasympathetic nervous system. It mainly works on muscarinic receptors (M1-5) in parasympathetic organs and nicotinic receptors (Nm and Nn) on autonomic ganglia and the neuromuscular junction.

Drugs targets in cholinergic transmission

Step	Drug Target	Examples
Synthesis	Block choline uptake	Hemicholinium-3
Storage	Prevent ACh packaging into vesicles	Vesamicol
Release	Inhibit ACh release	Botulinum toxin
Receptor binding	Stimulate or block receptors	Pilocarpine, atropine
Metabolism	Inhibit acetylcholinesterase	Neostigmine, physostigmine

Cholinergic receptors and their physiologic effects

Receptor	Location	Main Effects
M1	CNS and gastric glands	↑ gastric acid and salivation
M2	Heart	Bradycardia and ↓ AV conduction
M3	Smooth muscle & glands	Bronchospasm, diarrhea, urination, and glandular secretion
M3	Eye	Miosis, accommodation, and ↑ aqueous humor outflow
M4/M5	Brain	Modulates neurotransmission
Nm	Neuromuscular junction	Skeletal muscle contraction
Nn	Autonomic ganglia and adrenal medulla	Autonomic nervous system transmission and epinephrine release

Cholinergics (Cholinomimetics)

Direct-acting cholinomimetics

Drug	Key Features	Uses
Acetylcholine	M + N effects; rapidly destroyed	Rarely used
Bethanechol	Muscarinic only; resistant to cholinesterase	Urinary retention and neurogenic bladder
Methacholine	Mainly muscarinic	Bronchial challenge test
Carbachol	M + N; resistant to cholinesterase	Glaucoma and eye surgery
Muscarine	Non-selective muscarinic agonist	Toxicology relevance
Pilocarpine	Stable muscarinic agonist	Glaucoma and xerostomia
Cevimeline	Muscarinic agonist	Sjögren syndrome
Nicotine	Nicotinic agonist; crosses the BBB	Tobacco dependence

Reversible indirect-acting cholinomimetics (anticholinesterases)

Drug	Crosses the BB	Main Uses
Physostigmine	Yes	Anticholinergic poisoning
Donepezil	Yes	Alzheimer disease
Rivastigmine	Yes	Dementia
Galantamine	Yes	Dementia
Neostigmine	No	Myasthenia gravis and reversal of NMJ blockade. Commonly given with atropine/glycopyrrolate to prevent bradycardia
Pyridostigmine	No	Long-term treatment of myasthenia gravis
Edrophonium	No	Former Tensilon test. Has a rapid onset and short duration.

Irreversible indirect-acting cholinomimetics(anticholinesterases)

Drug	Main Use
Echothiophate	Glaucoma
Parathion	Insecticide
Malathion	Lice/scabies
Diazinon	Insecticide
Sarin, Soman, and Tabun	Nerve gases

Anticholinergics (Parasympatholytics)

Anticholinergics (parasympatholytics)

Drug	Uses
Atropine	Bradycardia and organophosphate poisoning
Scopolamine	Motion sickness and post-operative nausea and vomiting
Ipratropium	COPD and asthma
Tiotropium	COPD and asthma
Oxybutynin	Overactive bladder
Tolterodine	Urge incontinence
Solifenacin	Overactive bladder

Effects of atropine

System	Effects
Heart	Tachycardia
Eye	Mydriasis, cycloplegia
Lungs	Bronchodilation and reduced secretions
GIT	Reduced motility and constipation
Bladder	Urinary retention
Sweat glands	Hyperthermia

Reference Intervals ›

Biochemistry

ACTH	P: <80 ng/L
ALT	P: 5–35 U/L
Albumin	P: 35–50 g/L
Aldosterone	P: 100–500 pmol/L
Alk. phosphatase	P: 30–130 U/L
α-Amylase	P: 0–180 IU/dL
α-Fetoprotein	S: <10 kU/L
Angiotensin II	P: 5–35 pmol/L
ADH	P: 0.9–4.6 pmol/L
AST	P: 5–35 U/L
Bicarbonate	P: 24–30 mmol/L
Bilirubin	P: 3–17 μmol/L
BNP	P: <50 ng/L
CRP	P: <10 mg/L
Calcitonin	P: <0.1 mcg/L
Calcium (ionized)	P: 1.0–1.25 mmol/L
Calcium (total)	P: 2.12–2.60 mmol/L
Chloride	P: 95–105 mmol/L
Cholesterol	P: <5.0 mmol/L
VLDL	P: 0.128–0.645 mmol/L
LDL	P: <2.0 mmol/L
HDL	P: 0.9–1.93 mmol/L
Cortisol AM	P: 450–700 nmol/L
Cortisol Midnight	P: 80–280 nmol/L
CK ♂	P: 25–195 U/L
CK ♀	P: 25–170 U/L
Creatinine	P: 70–100 μmol/L
Ferritin	P: 12–200 mcg/L
Folate	S: 2.1 mcg/L
FSH	P: 2–8 U/L ♂; >25 menopause
GGT ♂	P: 11–51 U/L
GGT ♀	P: 7–33 U/L
Glucose (fasting)	P: 3.5–5.5 mmol/L
Growth hormone	P: <20 mu/L
HbA1C (DCCT)	B: 4–6%
HbA1C (IFCC)	B: 20–42 mmol/mol
Iron ♂	S: 14–31 μmol/L
Iron ♀	S: 11–30 μmol/L
Lactate (venous)	P: 0.6–2.4 mmol/L
Lactate (arterial)	P: 0.6–1.8 mmol/L
LDH	P: 70–250 U/L
LH	P: 3–16 U/L
Magnesium	P: 0.75–1.05 mmol/L
Osmolality	P: 278–305 mosmol/kg
PTH	P: 0.8–8.5 pmol/L
Potassium	P: 3.5–5.3 mmol/L
Prolactin ♂	P: <450 U/L
Prolactin ♀	P: <600 U/L
PSA	P: 0–4 mcg/mL
Protein (total)	P: 60–80 g/L
Red cell folate	B: 0.36–1.44 μmol/L
Renin (erect)	P: 2.8–4.5 pmol/mL/h
Renin (recumbent)	P: 1.1–2.7 pmol/mL/h
Sodium	P: 135–145 mmol/L
TBG	P: 7–17 mg/L
TSH	P: 0.5–4.2 mU/L
T4	P: 70–140 nmol/L
Free T4	P: 9–22 pmol/L
TIBC	S: 54–75 μmol/L
Triglycerides	P: 0.50–2.3 mmol/L
T3	P: 1.2–3.0 nmol/L
Troponin T	P: <0.1 mcg/L
Urate ♂	P: 210–480 μmol/L
Urate ♀	P: 150–390 μmol/L
Urea	P: 2.5–6.7 mmol/L
Vitamin B12	S: 0.13–0.68 nmol/L
Vitamin D	S: 50 nmol/L

Arterial Blood Gases

pH	7.35–7.45
PaCO₂	4.7–6.0 kPa
PaO₂	>10.6 kPa
Base excess	±2 mmol/L

Urine

Cortisol (free)	<280 nmol/24h
Hydroxyindole acetic acid	16–73 μmol/24h
Hydroxymethylmandelic acid	16–48 μmol/24h
Metanephrines	0.03–0.69 μmol/mmol cr.
Osmolality	350–1000 mosmol/kg
17-Oxogenic steroids ♂	28–30 μmol/24h
17-Oxogenic steroids ♀	21–66 μmol/24h
17-Oxosteroids ♂	17–76 μmol/24h
17-Oxosteroids ♀	14–59 μmol/24h
Phosphate (inorganic)	15–50 mmol/24h
Potassium	14–120 mmol/24h
Protein	<150 mg/24h
Protein/creatinine ratio	<3 mg/mmol
Sodium	100–250 mmol/24h

Haematology

WCC	4.0–11.0 ×10⁹/L
RBC ♂	4.5–6.5 ×10¹²/L
RBC ♀	3.9–5.6 ×10¹²/L
Hb ♂	130–180 g/L
Hb ♀	115–160 g/L
PCV ♂	0.4–0.54 L/L
PCV ♀	0.37–0.47 L/L
MCV	76–96 fL
MCH	27–32 pg
MCHC	300–360 g/L
RDW	11.6–14.6%
Neutrophils	2.0–7.5 ×10⁹/L (40–75%)
Lymphocytes	1.0–4.5 ×10⁹/L (20–45%)
Eosinophils	0.04–0.44 ×10⁹/L (1–6%)
Basophils	0–0.10 ×10⁹/L (0–1%)
Monocytes	0.2–0.8 ×10⁹/L (2–10%)
Platelets	150–400 ×10⁹/L
Reticulocytes	0.8–2.0% / 25–100 ×10⁹/L
Prothrombin time	10–14 s
APTT	35–45 s

Paediatric

Pulse Rate (bpm)
Neonate	140–160
Infant <1yr	120–140
1–5 years	110–130
5–12 years	80–120
>12 years	70–100
Respiratory Rate (tachypnoea)
0–2 months	≥60/min
2–12 months	≥50/min
1–5 years	≥40/min
>5 years	≥30/min
Blood Pressure (mmHg)
Term	65/45
1 year	75/50
4 years	85/60
8 years	95/65
10 years	100/70
Weight Formulas
3–12 months	(a + 9)/2 kg
1–6 years	2a + 8 kg
>6 years	(7a − 5)/2 kg
Haemoglobin (g/dL)
Term newborn	13–20
1 month	11–18
2 months	10–15
1–2 years	10–13
>2 years	11–14
MUAC (6 months–5 years)
Obese	>17.5 cm
Normal	13.5–17.4 cm
At risk	12.5–13.4 cm
Moderate malnutrition	11.5–12.4 cm
Severe malnutrition	<11.5 cm
Developmental Milestones
Social smile	1.5 months
Head control	4 months
Sits unsupported	7 months
Crawls	10 months
Stands unsupported	10–12 months
Walks	12–13 months
Talks	18 months
CSF WBC (/mm³)
Term newborn	0–25
>2 weeks	0–5

Calculator ›

Overview

Cholinergics (Cholinomimetics)

Anticholinergics (Parasympatholytics)

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