ANTICHOLINERGICS

Anticholinergics block the effects of acetylcholine and other cholinergic drugs at cholinergic
receptors of effector cells. Anticholinergics fall into two major families:

1. Antinicotinics which include ganglion blockers such as hexamethonium, trimethaphan, etc.,
   and neuromuscular blockers such as gallamine, tubocurarine, pancuronium, etc.
2. Antimuscarinics include tertiary amines such as atropine, scopolamine, tropicamide, etc,
   andquaternary amines such as propantheline, ipratropium, benztropine, etc.
   ATROPINE
   Atropine is found in the plant Atropa belladonna and it is the prototype of muscarinic
   antagonists.
   Pharmacokinetics
   Atropine is absorbed completely from all sites of administration except from the skin wall, where
   absorption is for limited extent; it has good distribution. About 60% of the drug is excreted
   unchanged in urine.
   Pharmacodynamics

Atropine antagonizes the effect of acetylcholine by competing for the muscarinic receptors
peripherally and in the CNS; therefore the effects of atropine are opposite to the acetylcholine
effects.
Organ-system Effects:
CNS: – lower doses produce sedation

• higher doses produce excitation, agitation and hallucination
  Eyes: – relaxation of constrictor pupillae (mydriasis)
• relaxation or weakening of ciliary muscle (cycloplegia-loss of the ability
  to accommodate)
  CVS: – blocks vagal parasympathetic stimulation (tachycardia)
• vasoconstriction
  Respiratory: – bronchodilatation and reduction of secretion
  GIT: – decreased motility and secretions
  GUS: – Relaxes smooth muscle of ureter and bladder wall; voiding is slowed.
  Sweat Glands: – suppresses sweating
• Clinical Indications
• Pre anesthetic medication -to reduce the amount of secretion and to prevent excessive vagal
• tone due to anesthesia.
• As antispasmodic in cases of intestinal, biliary, and renal colic
• Heart block
• Hyperhidrosis
• Organophosphate poisonings
• Side effects
• Dryness of the mouth, tachycardia and blurred vision
• Retention of urine
  Contraindications
  Glaucoma
  Bladder outlet obstruction.
  HYOSCINE (SCOPOLAMINE)

This drug has the same effect as atropine except for some differences which includes:-

• It has shorter duration of action
• It is more depressant to the CNS.
• All other properties are similar to atropine. It has certain advantage over atropine. These
  include:

1. Better for preanesthetic medication because of strong antisecretory and antiemetic action
   and also brings about amnesia
2. Can be used for short- travel motion sickness

1. SYNTHETIC ATROPINE DERIVATIVES
   There are a number of synthetic atropine derivatives, which are used in the treatment of various
   conditions, their actions are similar to that of atropine but have fewer side effects. These groups
   of drugs include
2. Mydriatic atropine substitutes, this group of drugs have shorter duration of action thanatropine and are used locally in the eye; drugs included: Homatropine, Eucatropine etc.
3. Antiseccretory antispasmodic atropine substitutes:
4. Effective more localized to the Gl. Drugs include: propantheline and hyoscine

3. Antiparkinsonian atropine substitute: – drugs like Benztropine, Trihexyphenidyl
4. Atropine substitutes which decrease urinary bladder activity like oxybutynin
5. Atropine substitutes used in bronchial asthma drugs like ipratropium