Autonomic Pharmacology 2 Flashcards
What drugs block cholinergic transmission at neuromuscular junctions?
Neuromuscular Blocking Drugs
What do neuromuscular blocking drugs act as?
Either:
- Antagonists (non-depolarizing)
- Agonists (depolarizing)
And inhibit release of ACH
What are the neuromuscular blocking agents?
- Tubocurarine
- Succinylcholine
- Botulinum toxin
What are some characteristics of Curare (d-tubocurarine)?
- “aarow poisons”
- Originally used as skeletal muscle relaxants
- Depolarization of membrane is inhibited and muscle contraction is blocked
- Causes weakness of skeletal muscles
How can competitive blockers be overcome?
By administration of cholinesterase inhibitors
What are some characteristics of succinylcholine?
- Attaches to nicotinic receptor and like ACH, results in depolarization
- Constant stimulation of receptor causes sodium channel to open, producing depolarization
- Flaccid paralysis
With succinylcholine, how long does the paraylsis last?
Only a few minutes because drug is broken down by plasma cholinesterase
What is succinylcholine used for?
- Endotracheal intubation
- Relax skeletal muscles during surgery
What does Botulinum Toxin do and what is it used for?
- Prevents calcium-dependedn release of ACH
- Produces state of denervation
- For muscles tics, muscle disorders, cosmetic procedures
What do ganglionic blocking agents do?
- Inhibit nicotinic receptors, so blocks nuerotransmission in both PANS and SANS
- Nicotine
- Trimethaphan
- Hexamethonium
What does nicotine do?
- Low doses - stimulation due to depolarization
- High doses - no response at nicotinic receptors, but stimulates muscarinic receptors
- Respiratory paralysis, increase BP, HR, GI motility and secretions
- Indication: tobacco cessation therapy, insecticide
What type of drugs act at receptors of the sympathetic nervous system?
Adrenergic drugs
What drugs fall under the adrenergic drugs category?
- Endogenous
- Epinephrine - adrenal medulla
- Norepinephrine - terminal nerve endings
- Dopamine - brian, splanchnic, renal vasculature
- Exogenous
- isoproternol
What are the different types of adrenergic receptors?
Alpha & Beta
What are the subtypes of Adrenergic drugs?
- Direct acting - produce effects by directly stimulating receptor
- Indirect acting - cause release of endogenous norepinephrine, which produces response
- Mixed action - either stimulate the receptor directly or cause release of norepinephrine
What does stimulation of Alpha Receptors cause?
- Vasoconstriction of vessels in skin (pale when scared)
- Protects you from bleeding if skin is damaged during trauma (“fight” response)
- Smooth muscle contraction
What does stimulation of Beta-1 Receptors cause?
- Cardiac stimulation
- Increased rate and force of contraction
- Breakdown glycogen to increase glucose (need energy during fight or flight)
What does stimulation of Beta-2 Receptors cause?
- Smooth muscle relaxation
- Vasodilation of vessels in skeletal muscle
- Bronchodilation
What do the adrenergic agonists (sympathomimetics) do?
- CNS excitation
- Increased peripheral resistance
- Increased blood pressure
- Dilates pupils
- Ease breathing
- Xerostomia
What are the clinical uses for adrenergic agonists?
- Vasoconstriction - (epinephrine) prolongs anesthetics and produce hemostasis
- Decongestants - vasoconstriction of blood vessels in nose
- Treatment of shock - elevate low BP
- Treatment of cardiac arrest - epinephrine jump starts heart
- Asthma & emphysema - bronchodilation
- CNS stimulation - amphetamines (stimulants) used to treat ADD/ADHD
What are some popular adrenergic agonists (non-catecholamines)?
- Albuterol
- Amphetamines
- Clonidine
- Dopamine
- Oxymetazoline
- Phenylephrine
- Phentermine
- Pseudoephedrine
- Tetrahydrozoline
What are some characteristics of Albuterol?
- Beta2 adrenergic agonist
- Potent bronchodilator
- “Rescue drug” - asthma & COPD
- Incuded in all dental office emergency kits for managing acute asthma attack
What are the side effects of Adrenergic Agonists?
- Anxiety/irritability
- Tremors
- Cardiac arrhythmias (tachycardia)
- Hypertension
- Constipation
- Urinary retention
What do Alpha Antagonists (blockers) do?
- Block vasoconstriction in skin
- Decrease total peripheral resistance
- Decrease blood pressure
- Reverse dilation of pupils
