Anticholinergics

Front 1

What are the 2 drugs that are anticholinergic?

Back 1

Atropine and Glycopyrrolate.

Front 2

Atropine. What are the 3 MOA?

Back 2

1) It blocks stimulation by acetylecholine of autonomic postganglionic receptors with muscarinic properties ( postganglionic parasympathetic stimulation). Atropine is a competitie antagonist at these receptors. Receptor stimulation in salivary, secretory and some sweat glands, cardiac muscle and smooth muscle are blocked by atropine.
2) When parasympathetic impulses are blocked, the sympathetic impulses dominates and hence HR increases.
3) All reflex vagal mediated responses are blocked.

Front 3

What 4 actions does Atropine have on the cardiovascular system?

Back 3

1) Tachycardia.
2) A transient slowing of the heart occurs when given IM or SC. IV is preferred during anasethesia.
3) Increase CO and BP because of tachycardia.
4) Myocardial depression is possible if overdose.

Front 4

What 2 actions does Atropine have on the respiratory system?

Back 4

1) Secretion by glands in the resporatory tract is inhibited by atropine.
2) Atropine inhibits contraction of bronchiolar smooth muscle, thus dilating the small airways. While respiratory dead space is increased, airway resistance to gas flow is reduced.

Front 5

What 3 actions does Atropine have on the GI system?

Back 5

1) GI smooth muscles are relaxed by atropine thereby reducing or abolishing muscle tone.
2) Rumen motility is inhibited.
3) GI secretions are inhibited, very high doses are required to inhibit gastric secretions.

Front 6

What effects does atropine have on the eye, UT and CNS?

Back 6

By blocking cholinergically innervated sphincter muscles of the iris, atropine produces mydriasis. This effect interferes with ocular signs of anaesthesia. It relaxes smooth muscles in the urinary tract. XS large doses will cause excitement to CNS.

Front 7

What are the 3 uses of atropine?

Back 7

1) Decrease salivation and secretions in the resp tract. Useful for cats and dogs given ketamine which increases secretions. Salivations is not a problem with dogs or horses. Rarely given to ruminants.
2) Inhibit vagal activity producing bradycardia. It may increase with inhalational anaesthetics in low doses and during eye surgery ( pressure ont he external muscles of the eye stimulate oculocardiac reflex. )
3) Prevent stimulation of muscarinic receptors.

Front 8

Disadvantages of Atropine. (6)
-heart
-eye
-GI

Back 8

1) Tachycardia. NOt recommended in animals with tachy, avoid in myocardial failure. Myocardial o2 comsumption increases with tachy which raises the potential for arrythmias.
2) Due to sympathetic dominance of the autonomic control of the heart , incidence of cardiac arrthmias usually increases in the presence of atropine.
3) Mydriasis . May cause excitement in horses.
4) GI relaxation. Post operative ileus and colic may occur in horses due to decreased GI motility.
5) Above are sig rxn therefore given when required only.
6) All alpha 2 agonists slows heart down. Not recommended to be given with atropine.

Front 9

What is Glycopyrrolate?

Back 9

It is an anticholinergic drug that is similar to atropine but is more potent and has a longer duration in action.

Front 10

Name 4 pharmalogical actions of Glycopyrrolate.
- actions on the heart
- what does it not cross?
- respiratory
- GI

Back 10

1) It blocks vagal action but the secondary increase in heart rate and blood pressure are less of a problem than with atropine. Arrythmias are less likely.
2) Does not cross BBB and placental barrier.
3) Decrease in respiratory secretions. Some dilution of the small bronchi may occur.
4) There is a decrease in GI motility.