Ch 14 + 15: Adrenergic Agonists + Cholinergic Antagonists Flashcards
Adrenergic Agonists: Catecholamines
- short duration of action
- destroyed rapidly by monoamine oxidase (MAO)
- COMT (catechol-O-methyltransferase) is one of several enzymes that degrade catecholamines, such as dopamine, epinephrine, norepinephrine
- no PO - must be parenteral or inhalation d/t COMT in intestinal tract
- doesn’t cross BBB
why can’t catecholamines be taken PO?
“eats” cates b4 enter bldstream & to target tissue
- broken down before it is absorbed
Adrenergic agonists: noncatecholamines
- may be taken PO
- not destroyed as rapidly
- better able to enter brain + affect CNS
Epinephrine: Considerations
Nonselective adrenergic agonists - activate alpha, beta receptors, for bronchospasm, cardiac arrest + hypotension
- assess underlying problem + preexisting conditions
- hx / px (VS)
- closely monitor resp status
- use cardiac monitor/resuscitation equipment
- monitor BP closely
- inform prescriber of changes in I&O
- monitor for hyperglycemia - insulin gtt
- examine ocular + nasal mucosa
- protect from light (brown bag/IV)
Alpha 1 Agonists - Phenylephrine: Contraindications / precautions
to relieve nasal decongestion + elevate BP
- severe HTN
- pre-existing bradycardia
- advanced CAD
- nitroglycerin
- narrow-angle glaucoma
- hyperthyroidism
- diabetes
Alpha 1 Agonists - Phenylephrine: treatment of overdose
- phentolamine
- anti-dysrhythmic drugs
Alpha 1 Agonists - Phenylephrine: Considerations
- examine IV site frequently
- advise pt to remove contact lenses
- dark eye protection after ophthalmic admin (dry out eyes + nasal airways)
- avoid caffeine (w/ all adrenergic agonists)
- contact HCP if palpitations or jittery/nervousness
Muscarinic Antagonists - what is used?
belladonna - natural source of alkaloids w/ anticholinergic activity
Muscarinic Antagonists - Uses
- GI disorders such as IBS
- opthalmic procedures
- cardiac rhythm disorders
- chemotherapy induced diarrhea
- adjuncts to anesthesia (decr secretions)
- asthma + COPD (bronchodilation effects)
- antidotes for poisoning or overdose
- urge incontinence (overactive bladder), helps w/ spasms - watch BPH
- Parkinson disease
Muscarinic Antagonists - AEs
relatively high incidence of AEs - why it is rarely the drug of choice
- urinary retention
- xerostomia (dry mouth)
- tachycardia
- CNS stimulation
- dry eyes
- photophobia
- urinary retention in BPH
Anticholinergic syndrome: what is it & what’s the antidote?
= overdose of muscarinic antagonists
- dry mouth, difficulty swallowing
- visual changes, blurred vision, photophobia
- agitation + hallucinations
antidote = physostigmine
- generally only admin to pts showing severe symptoms
Nicotinic antagonists: Neuromuscular blockers - what do they work on?
work on muscle, NOT CNS or motor/sensory perceptions
Nicotinic antagonists: Neuromuscular blockers - how do they work?
motor end plate of muscle: causes relase of Ach to travel to receptors on skeletal muscle = muscle contraction
continuous depolarized state in which Ca doesn’t return to its storage depots =
- sustained muscle contraction + paralyzed condition necessary for certain surgical procedures
Nicotinic antagonists: Neuromuscular blockers - Depolarizing
Succinylcholine
- given to produce muscle paralysis duringn short medical-surgical procedures
- watch for contraction to signal access - preceded by contraction
- initial contraction and then muscle is relaxed –> paralyzed
- restlessness = no success
Nicotinic antagonists: Neuromuscular blockers - Nondepolarizing
Tubocararine
- given to produce muscle paralysis during longer surgical procedures
- occupies Ach receptors and causes muscle paralysis w/o depolarization (no contraction
- = flaccid paralysis
Succinylcholine: AEs
- complete paralysis of diaphragm/intercostal muscles - watch for resp paralysis
- tachycardia
- hypotension
- urinary retention
Succinylcholine: Serious AEs
- malignant hyperthemia - muscles rigid, skin hot
- resp depression
- apnea
- dysrhythmias
Succinylcholine: Black Box Warning
- children w/ congenital musculoskeletal diseases at greater risk for cardiac arrest
- no way to predict which pts at risk
Succinylcholine: therapeutic effects + uses
- surgical anesthesia
- pseudochlinesterase
- relaxes abdo muscles, or for relaxation prior to intubation
- induces relaxation in less than 1 minute
- muscle strength returns quickly after discontinuation of drug
- pt can still feel pain, is aware of surroundings (use benzos + opioids)
Tubocurarine - what is it for?
- nondepolarizing neuromuscular blockers (NDNBs)
- tubocurarine = prototype, 9 others in class
- used to relax skeletal muscles during surgical procedures
- don’t cause sedation, analgesia, or loss of consciousness –> must use benzos, propofol & opioids in conjunction
