Mzantsi Medics

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Drug class

Anticholinergic / anti-muscarinic.

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Atropa belladonna

Atropine is a belladonna alkaloid. The atropa belladonna plant contains alkaloids such as atropine, hyoscine, and scopolamine. It is mainly found in Mediterranean countries, North America, Western Europe and Himalayas.

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Mechanism of action

Atropine is a competitive antagonist at the muscarinic receptor which competes with acetylcholine for receptor binding. It blocks parasympathetic effects that would be caused by acetylcholine.

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Indications for atropine

• Unstable bradycardia with a pulse.
• Premedication for drug induced intubation or rapid sequence intubation in order to prevent bradycardia.
• Used as an antisialagogue for anaesthetic procedures.
  • Also read up on glycopyrrolate
• Atropinization for organophosphate and carbamate poisoning.
• Iritis and cyclitis
• Mydriasis caused by atropine allows ophthalmoscopic examinations of the retina relive
• Relief of intestinal spams
• Hyperactive bladder treatment.

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Atropine side-effects

• Dry mouth
• Blurred vision 
• Photophobia 
• Raised intraocular pressure
• Anhydrous 
• Flushing 
• Dysrhythmias 
• Urinary retention 
• Constipation 
• Urticaria
• Skin rashes 
• Nervousness
• Dizziness,
• Confusion 
• Nausea,
• Loss of balance
• Drowsiness
• Excitement

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Contraindications for atropine usage

• Known atropine allergy
• Closed angle glaucoma
• Urinary retention
• Pyrexia
• Thyrotoxicosis
• Conditions with gastrointestinal tract atony
• Myasthenia gravis
• Pyloric stenosis

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Dosage (Adults)

• Bradycardia with pulse.
  • 1 mg IV every 3 to 5 minutes to maximum of 3 mg.

• Organophosphate and carbamate poisoning.
  • Atropinization as soon as possible after airway is secured.
    • Atropine 1 – 2 mg initial dose.
    • After every 5 minutes double the previous dose of atropine give. See diagram 3 below.
    • Stop if:
      • Respiratory secretions have dried up and there is absence of bronchoconstriction
    • Begin atropine infusion after respiratory secretions had stopped.
      • 3 mg/hour or 0.02 – 0.08mg/kg/hr
      • Stop atropine infusion if signs of toxicity develop.

• Premedication:
  • 0.2 – 0.5 mg intravenously just before induction. 
  • 0.2 – 0.5 mg intramuscularly 45 minutes before induction.

• Postoperatively
  • 0.5 – 1 mg.
  • With neostigmine.

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Pharmacokinetics

• There is good absorption of atropine when injected intramuscular. 
• Atropine crosses the blood brain barrier and also crosses the placenta.
• The ½-life of atropine is between 12.5 hours to 38 hours.

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Dose-dependent receptor sensitivity

Atropine does not have the same degree of sensitivity on all organs and the sensitivity on peripheral organs is dose-dependent. Receptors that are highly sensitive to atropine are situated in salivary glands, bronchial glands, sweat glands and lesser sensitive receptors are located in the eyes, heart and gastrointestinal tract.

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Other anti-muscarinic agents

• Ipratropium
• Scopolamine

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Closing remarks

Healthcare providers must always remember to use the local guidelines and protocols. Healthcare providers must also remember to consult specialists early as they are continuing with the management of patient. Often, patient management will need to tailored according to the specific case.

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Bibliography

Ainslie G, Ascott-Evans BH, Barnes KI, et al (2010). Cardiovascular system. In South African Medicine Formulary: 136-137. Edited by Rossiter D. Cape Town. FA Print.

Anaesthesia, u. In (no date) management of organophosphorus poisoning, wfsahq.org. Available at: https://resources.wfsahq.org/wp-content/uploads/uia-19-management-of-organophosphorus-poisoning.pdf (accessed: july 23, 2023).

Chapter 7 Acetylcholine Receptor Antagonists. In Pharmacology: 63-65. Edited by

Brunton L.L., Parker K.L., Blumenthal D.K. & Buxton I.L.O. (2008). Chapter 7 Muscarinic Receptor Agonists and Antagonists. In Goodman & Gilman’s Manual of Pharmacology and Therapeutics. Edited by Brunton L.L., Parker K.L., Blumenthal D.K. & Buxton I.L.O. USA. The McGraw-Hill Companies

McLendon, K. and Preuss, C. V. (2023) Atropine. StatPearls Publishing.

Mycek M.J., Harvey R.A. & Champe P.C. (). Cholinergic Antagonists. In Lippincott’s Illustrated Reviews: Pharmacology Edited by Harvey R.A. & Champe P.C. USA. Lippincott Williams and Wilkins.

Organophosphate toxicity medication (2023) Medscape.com. Available at: https://emedicine.medscape.com/article/167726-medication?form=fpf (Accessed: July 23, 2023).

Robb, E. L. and Baker, M. B. (2023) Organophosphate Toxicity. StatPearls Publishing.

(No date) Epa.gov. Available at: https://www.epa.gov/sites/default/files/documents/rmpp_6thed_ch5_organophosphates.pdf (Accessed: July 23, 2023).