User Tools

Site Tools


atropine

atropine

History:

  • alkaloid from the deadly nightshade (Atropa belladonna) & in Jimson weed plant (Datura stramonium) & other of genus Solanaceae;
  • Was used by ancient Hindus, Roman Empire, etc. as poison;
  • Used by Italian women to dilate eyes → inc. sex appeal;
  • Used in India by inhaling Jimson weed smoke to Rx asthma;
  • Introduced into UK in early 1800's; Isolated 1831;
  • Showed blocked vagal cardiac effects (1867);

Actions of atropine:

  • Competitive antagonist of ACh at muscarinic receptors;
    • → mydriasis, cycloplegia, tachycardia, antispasmodic GIT;
    • → dry mouth, decr. fasting gastric acid secretion; decr. motility;
    • → dilates pelves, calyces, ureters, bladder;
    • → delayed emptying of GB after fatty meal;
    • → dry, hot skin;

Stability & preparation:

  • Racemic mixture of dextro- & l-hyoscyamine (mainly l- form active);
  • IV: 400,600,1200 µg/ml in 1ml ampoules;
  • oral: combined with other belladonna alkaloids;

Absorption:

  • Rapidly absorbed GIT; Some from mucosa; Limited via skin;
  • Peak 15-50min post-IM;

Distribution:

  • throughout body;

Metabolism & Excretion:

  • T1/2 approx4hrs; Half metab. in liver & half excreted urine;

Side effects of atropine:

  • blurred vision; dry mouth; hyperthermia (esp. infants);
  • constipation; urine retention; tachycardia (esp. fit young adults);
  • precipitate glaucoma;
  • NB. low dose may cause initial mild bradycardia;

Toxic effects (may last 48hrs or more):

  • Overdoses are remarkably safe in ADULTS but DANGEROUS in CHILDREN!
    • Children much more susceptible to toxic effects esp. hyperthermia (except tachycard.);
    • Although recovery has occurred in children with 400mg, death has occurred with 2mg !!
  • tachycardia with weak pulse; iris practically obliterated;
  • skin flushed, hot, dry & scarlet; ataxia; restlessness; excitement;
  • delirium; toxic psychoses (sometimes even from top.ophth. use!); coma;
  • ie. “Dry as a bone, blind as a bat, red as a beet, mad as a hatter”

Routes of Administration & Dosage:

IV:

  • organoP poisoning - 1-6mg repeat 2mg every 5-60min. (max 50g/d?)
  • with neostigmine - 0.6-1.2mg slowly 10-15min before neostigmine;

IM:

  • antispasmodic - 0.6mg IM tds prn;
  • premed - 0.3-0.6mg or 20µg/kg (if <5kg→60µg);

Oral:

  • usually combined with other Belladonna alkaloids;

Contraindications to atropine:

  • obstructive GIT dis.: PS; cardiospasm; paralytic ileus; atony;
  • obstructive uropathy: bladder neck obstruction with prost.hypertrophy;
  • high environmental temperature esp. children;
  • closed angle glaucoma;
  • care in tachycardics: thyrotoxicosis; cardiac failure;
  • COAD as may → thicker inspissated secretion → bronchial plugs;

Major interactions:

  • other anticholinergic drugs: antihist.; haloper.; tricyc.; phenoth.;
  • incompatible with: adrenaline; bicarb; most antibiotics; barbiturates
atropine.txt · Last modified: 2011/08/25 21:36 (external edit)