Antimuscarinics

Question 1

Atropine

• -structure
• -derived from
• -what receptors does it effect?

Answer 1

an ester between tropanol and tropic acid

leaves of atropa belladonna

blocks the muscarinic not nicotinic receptors

Question 2

What effects are seen when atropine is given at 0.5 mg?

Answer 2

some dryness of mouth

inhibition of sweating

Question 3

What effects are seen when atropine is given at 2 mg?

Answer 3

marked dryness of mouth
rapid HR
dilated pupils

Question 4

What effects are seen when atropine is given at 10 mg?

Answer 4

Symptoms from 0.5 mg and 2 mg are more marked

```
ataxia
restlessness
excitement
hallucination
delirium
^CNS effects
~~~

Question 5

What is atropine used for in the eye?

• -general
• -specific
• -example drugs

Answer 5

–mydriatic (dilates the pupil)

so used

• -to dilate pupil in eye exam
• -when torn iris (b/c iris is an active mm that is constantly altering to the amount of light)
• -to break synechiae that occur with herpes infections in the eye

cyclopentolate
tropicamide

Question 6

What are the advantages of cyclopentolate and tropicamide?

Answer 6

They have a quicker onset and a shorter duration than atropine itself

cyclopentolate - 45 min onset, 15 hr duration
tropicamide - 30 min onset, 4 hr duration

Question 7

What is atropine used for in the respiratory system?

Answer 7

antimuscarinic to decrease respiratory secretions

• -preanesthetic mediation
• -decrease accumulation of fluid in lungs
• -block excess vagal activity in anesthesia and surgery

Question 8

What is atropine used for in the GI system?

Answer 8

• -antispasmodic effect
• -IBS
  
  • –common problem
  • –spastic constipation or diarrhea
• -may contain small amounts of atropine or scopolamine and mild sedative

Question 9

What is atropine used for in the urinary system?

Answer 9

antimuscarinics in urinary incontinence (enuresis)

• -increasingly common in elderly and also occurs in children (30% of 4 yo)
• -durgs are competitive blockers of muscarinic receptors)
• -drugs effective but dryness of mouth and eyes limit tolerability

Question 10

What atropine analogues are used for enuresis?

Answer 10

1. oxybutinin
2. tolterodine
3. solifenacin

Question 11

oxybutinin

Answer 11

7x stronger than atropine as antispamoid but only 20% of dry mouth problems

Skin patch even more tolerable

Question 12

tolterodine

Answer 12

more tolerable than oxybutinin

Question 13

solifenacin

Answer 13

reduced xerostomia and constipation

Lasts 24 hr

Has specificity for M3, so don’t see any effects on the heart – its the best selling antimuscarinic on the market

Question 14

What are antimuscarinics used for in the respiratory system?

Examples - their use, advantage, etc.

Answer 14

Treatment of bronchoconstriction

decreases hyperactive vagal reflex

Ipratropium inhaler
Tiotropium lasts 24 hours
^^ both quaternary, not absorbed
–no decreases ciliary activity; little drying

Question 15

What is the cardiovascular use for antimuscarinics?

Answer 15

For sinus bradycardia after MI

Used to block excess vagal activity

Use it cautiously to restore cardiac output

Question 16

Receptor specificity of atropine

Answer 16

Relatively non-specific

Good for M2 and M3, but less effective on M1

Question 17

Can antimuscarinics effect the CNS?

Answer 17

Yes. Tertiary amine antimuscrinics can enter the CNS
–includes atropine, scopolamine, mydriatics, and drugs for enuresis

Cause restlessness, ataxia, hallucinations
In high doses, cause psychosis
Children and elderly esp susceptible

Question 18

What is the antidote for excess antimuscarinics effecting the CNS?

Answer 18

physostimgine

Question 19

What antimuscarinics are used for IBS?

Answer 19

Methoscopolamine

• -quaternary amine
• -no CNS effects

Dicyclomine
–“direct” effect on smooth mm

Question 20

What precautions should be taken when using antimuscarinics? AKA when should you not use it?/what should you be aware of as side effects?

Answer 20

1. Bad heart
   
   • -atropine can increase HR
   • -vagal activity less in infancy and old age
2. Intestinal atony
3. Eye infection
4. Lung infection
5. Blurred vision
6. Glaucoma
7. Prostatic hypertrophy
8. Block sweating

Question 21

Mnemonic for remembering atropine/antimuscarinic side effects

Answer 21

Dry as a bone, blind as a bat, red as a beet, mad as a hatter