Atropine

Pharmacokinetics and Metabolism

In medical practice, the substance is used as a salt—atropine sulfate. As a treatment for parkinsonism, it is significantly inferior to modern central muscarinic antagonists (such as trihexyphenidyl and biperiden) because it causes too many peripheral adverse effects.

• Routes of administration: per os (oral) 30–40 minutes before meals, parenterally, or topically (as eye drops).
• Absorption and distribution: The drug is readily absorbed from the gastrointestinal tract. Due to its high lipophilicity, it crosses the blood-brain barrier within 30–60 minutes and accumulates in the central nervous system.
• Biotransformation: Metabolized in the liver via hydrolysis into inactive components: tropine and tropic acid.
• Elimination: The half-life is about 2 hours. Between 30% and 50% of the substance is excreted unchanged in the urine.

When taken orally, the duration of the therapeutic effect lasts from 4 to 6 hours.

Adverse Effects and Contraindications

All adverse reactions of atropine are a pharmacodynamic extension of its primary action: systemic blockade of muscarinic receptors in various organs. Contraindications directly stem from these effects.

1. Eye: Causes cycloplegia (paralysis of accommodation), impairing near vision (patients cannot focus on close objects). Because the drug increases intraocular pressure, it is strictly contraindicated in glaucoma.
2. Cardiovascular system: By blocking vagal influences, atropine induces marked tachycardia. Contraindicated in tachyarrhythmias.
3. Gastrointestinal tract: Decreases smooth muscle tone and peristalsis while increasing sphincter tone, leading to severe obstipation (constipation). Contraindicated in intestinal atony.
4. Urinary system: Relaxes the urinary bladder wall (detrusor) and spasms the sphincter. Due to the high risk of acute urinary retention, it is contraindicated in benign prostatic hyperplasia (BPH).
5. Secretory function: Inhibits salivary gland secretion, causing severe dry mouth (xerostomia).

Acute Poisoning: Clinical Presentation

Poisoning most commonly occurs in children who ingest toxic plants such as deadly nightshade (Atropa belladonna), jimsonweed (Datura), or henbane (Hyoscyamus). Other causes include medication overdose (including systemic absorption from eye drops) or cross-toxicity with other drugs exhibiting anticholinergic activity (amitriptyline, imipramine, chlorpromazine).

The clinical picture is divided into two major symptom groups:

• Peripheral manifestations: Persistent mydriasis (pupillary dilation), photophobia, and blurred vision. The lack of lacrimal fluid creates a sensation of "sand in the eyes." Severe thirst, dryness of the oral and pharyngeal mucosa, and dysphagia are observed. The skin becomes flushed (hyperemia), and hyperthermia develops—temperatures can reach 42 °C in children due to sweat gland blockade. Cardiac findings include marked tachycardia (160–190 bpm), extrasystoles, and a risk of myocardial ischemia. Urinary bladder atony may occur.
• Central manifestations: The initial stage is dominated by motor and psychiatric agitation. "Atropine psychosis" develops, characterized by visual and auditory hallucinations, severe agitation, delirium, and impaired coordination and memory. Seizures may occur. In the terminal stage, psychosis gives way to CNS depression and coma. Death results from respiratory center paralysis.

Principles of Treatment for Poisoning

Management requires a comprehensive approach, including antidote administration, detoxification, and supportive care.

1. Antidotes (pathogenetic therapy): Administration of anticholinesterase agents capable of crossing the blood-brain barrier (physostigmine, galantamine). They increase the concentration of endogenous acetylcholine, which competitively displaces atropine from receptor binding sites.
2. Toxin removal (detoxification): Gastric lavage with potassium permanganate solution, administration of activated charcoal and saline laxatives. Tannin or strong tea can be used to bind alkaloids. In severe cases, active detoxification methods such as hemoperfusion and forced diuresis are used.
3. Supportive care: Diazepam or short-acting barbiturates are used to control psychomotor agitation. Mechanical ventilation is initiated if respiratory depression occurs.

Belladonna Preparations

Belladonna extracts (dry and thick) and tinctures contain atropine as their primary active ingredient. They belong to the group of antispasmodics and are prescribed for painful smooth muscle spasms of the gastrointestinal tract and biliary tract.

There are numerous combination belladonna products:

• Tablets: Becarbon, Besalol, Bepasal, Bellalgin.
• Suppositories: Betiol, Anuzol.
• Drops: Zelenin drops.