L 18 Flashcards
Name the M3 specific antagonists
Tolterodine
Solifenacin
Belladonna plant think:
Atropine
Scopolamine
Differences between atropine and scopolamine
Atropine: no CNS, effects are peripheral, CNS effects only at high doses
Scopolamine: Quick CNS penetration=> sedation, amnesia, euphoria,
What M antagonist is used to dilate the eye?
Tropicamide
Ipratropium
M Antagonist
No CNS, poor oral absorption
Inhaled to treat COPD
Tropicamide
M Antagonist
Used to dilate the eye
What is used with atropine to prevent diarrhea?
Diphenoxylate (Lomotil)
Drugs used after prostate surgery
Oxybutinin
Trospium
To prevent bladder spasm
Dose dependence of atropine
Blocking M receptors has most effect on tissues where there is high PS tone. From low to high dose, will affect:
Glands=> dec sweat and salivation
Heart=> tachycardia
Eyes=> blurred vision
GI/GU=> bowel problems, bladder problems
Brain=> ataxia, hallucinations, delerium, coma
Atropine
M antagonist
No CNS
Scopolamine
Quick CNS access
Causes sedation, amnesia
Treats nystagmus and motion sickness
Role of M antagonists in Parkinson’s
In parkinson’s disease and with antipsychotic drugs, Dopamine is blocked or reduced. M antagonists block Ach to help restore balance between the two chemicals in the corpus striatum.
Benztropine is commonly used
Effects of anticholinergic M antagonists on the eye
Blocking M receptors blocks sphincter pupillae and the ciliary muscle causing mydriasis and cycloplegia.
Pupil dilation blocks flow of humor causing increase in intraocular pressure.
M antagonists used for eye dilation
Tropicamide Homatropine Both short-acting Also cause increase intraocular pressure Only used in open-angle glaucoma that is well managed
Cholinergic antagonist effects on heart
Low dose of Atropine causes bradycardia by inhibiting presynaptic M2=> inc Ach release
Mod dose of Atropine causes tachycardia because of dec M2 action on SA node and:
Decreased M2 inhibition on symp nerve=> inc NE release
Larger effect on young adults with lots of Vagal tone, less effect on babies and elderly with lower Vagal tone
Blocking vagal tone => inc AV conduction which can cause arrhythmias
To overcome an AV heart block, what can be given?
Atropine helps by decreasing vagal tone and increasing AV conduction
M antagonist effects on lungs
Blocks M3=> bronchodilation
Helpful in acute asthma, but not chronic
Drugs of choice for COPD
Drug used to prevent cardiac vagal response when handling organs
Glycopyrrolate
Dicyclomine
M antagonist
prevents GI spasms
Ipratropium
M antagonist
used for acute asthma or COPD
Not absorbed well, effects remain localized to lung
Tolterodine
M3 antagonist
For bladder overactivity
Low lipid solubility
Low CNS
Oxybutynin
M antagonist
Prevents bladder spasm after prostate surgery
Glycopyrrolate
M antagonist
Useful for heart
Also useful to decrease GI symptoms when using Neostigmine for Myasthenia Gravis
Contraindications for antimuscarinic drugs
Uncontrolled or narrow-angle Glaucoma
Males with BPH because would cause urinary retention
Treatment of mushroom overdose or organophosphate poisoning
IV atropine until mouth dry and mydriasis occurs