Cholinoceptor Antagonists Flashcards
What does hexamethonium do?
First anti hypertensive drug used but has lost of side effects as very general - primarily an ion channel blocker
What does trimetaphan do?
Used when you want hypotension during surgery, IV administered short acting receptor antagonist
What does atropine do to CNS at normal and toxic dose
Normal - little effect
Toxic - hot as a hare, blind as a bat, dry as a bone, red as a beet, and mad as a hatter
What does hyoscine do at normal and toxic dose?
Normal dose - sedation, amnesia
Toxic dose - CNS depression or paradoxical CNS excitation associated with pain (probs bc of greater permability of BBB)
What does tropicamide do?
Used in examination of retina and causes dilation/miosis
What does hyoscine patch do?
Inhibit muscarinic receptoes in vomiting centre so the sensory mismatch of eye see and labyrinth reports in balance. Can’t induce vomiting from motion sickness
What do MRA drugs do in parkinsons?
Substantia nigra neurones that are lost usually produce dopamine. Lack of dopamine causes parkinsons symptoms, but MRA drug decreases the negative inhibition on release of dopamine from another source into striatum
What are the effects of ipratropium bromide?
Used in asthma and COPD as causes bronchodilatoon and has a similar molecule shape to atropine but w extra B so lingers more in lungs as can’t cross mucosa as easily as atropine
How do you treat atropine poisoning
Anticholinesterase eg physostigmine
What are examples of muscarinic receptor antagonist drugs?
Atropine Hyoscine Tropicamide Hyoscine patch Ipratropium bromide
What are the unwanted effects of muscarinic receptor antagonists?
Hot as hell - decrease in sweating and thermoregulation defects
Dry as a bone - decreased secretions
Blind as a bat - cyclopegia (paralysis of eye muscles so no accomodation)
Mad as a hatter - CNS disturbance eg tremours
How does botulinum toxin work?
Binds to ACh vesicles and stops them docking with the inner membrane to form SNARE complexes
How do MRAs work as anaesthetic pre-medication?
They block PNS so block bronchoconstriction and watery secretions, decrease HR and contractility and also sedates the patient
What are the GI effects of MRAs? How do they treat irritable bowel syndrome?
decreases GI tone and secretions
