atropine

see also anti-muscarinic anticholinergic agents

• 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);

• 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;

• 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;

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

• throughout body;

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

• 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;

• 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”

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

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

• usually combined with other Belladonna alkaloids;

• 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;

• other anticholinergic drugs: antihist.; haloper.; tricyc.; phenoth.;
• incompatible with: adrenaline; bicarb; most antibiotics; barbiturates