Sympathomimetics Flashcards
What are medical uses of sympathomimetics?
Bronchodilation Nasal decongestion Relieve acute hypersensitivity reactions Raise BP Relieve adrenergic insufficiency Stimulate heart
Sympathomimetics as bronchodilators
B2 stimulants used to relieve bronchoconstriction in COPD
Receptors involved
- -B2
- -alpha 1
- -B1 action
- –side effect
Sympathetic bronchodilators can be used to ..
diagnose the cause of airway constriction
may be due to inflammation or bronchiolar spasm
B2 stimulants act in seconds
Which adrenergic receptors does epinephrine work on?
alpha 1
beta 1
beta 2
Which adrenergic receptors does albuterol work on?
beta 2
Which adrenergic receptors does metaprotere nol work on?
beta 2
Which adrenergic receptors does almeterol work on?
beta 2
Aside from just bronchodilating, what do bronchodilators do?
Increase ciliary activity
Inhibit histamine and leukotriene release
(leukotrienes are powerful bronchoconstrictors)
Why are Beta2 agonists drugs of choice?
- Most effective bronchodilators
- Tolerance with continued use overcome by increasing dose, usually
- Receptor down-regulation prevented or even partly reversed with corticosteroids
What are precautions for using adrenergic bronchodilators?
- -“benign essential tremor” due to B2 stimulation
- -feelings of anxiety may limit use
- -increases blood sugar
- -a1 and b2 receptors mobilize liver glycogen
- -dry pharyngeal membranes
- -problem with epinephrine (vasoconstriction)
Sympathomimetics as nasal decongestants
–MOA
alpha 1 agonists constrict dilated blood vessels and relieve nasal stuffiness and headache
Examples of sympathomimetics used as nasal decogestants
Phenylephrine
–P.O. as nose drops or nasal spray
Pseudophedrine
- -Still “widely available”
- -CNS stimulant
Oxymetazoline
–Long duration
Adverse reactions to nasal decongestants
Transient burning
Rebound congestion
Chemical rhinitis
CNS depression, hypotensio (imidazoline effect)
Adrenergics in acute hypersensitivity
May involve foods, pollon, drugs, animals
B2 stimulants inhibit antigen-indcued histamine release
Epinephrine used
Sympathomimetics are used in hypotension. Why is this important?
Necessity for “pressor” effect
- -below 40 mm Hg diastolic or 50 mm Hg systolic
- –critical decrease in flow to heart, brain, and also gut, liver, kidney
Need to bring the pressure back up!
What are some clinical situations in which there is a decrease in blood pressure?
General and spinal anesthesia
Drug overdose
Acute renal failure
Shock (sympathomimetics not used)
What are two ways to increased blood pressure via drugs?
- increase CO with beta1
2. increase peripheral resistance with alpha1
Which drugs are used to increased BP via increase in peripheral resistance?
Norepinephrine
Alpha-1 stimulants - e.g. phenylephrine
These work on alpha 1
Which drugs are used to increased BP via increase in CO?
Dopamine
Dobutamine
These work on beta1
Short acting pressor agents are substrates for…
NET and ENT
Long acting pressor agents are used for …
smoother pressure control
Dopamine
Some b1
Dilation of renal, coronary, and mesenteric beds (D1 receptors)
Dobutamine
B1, but little increase in HR
Precautions in using “pressor” agents
- Hyperthyroidism (excess receptors)
2. Necrosis on prolonged vasoconstriction (when used over a long time) – liver and kidney
Disease states that show adrenergic deficiency
Pure Autonomic Failure (PAF)
–disease of post ganglionic sympathetic nerves
Postural Tachycardia Syndrome (POTS)
Multiple System Atrophy (MSA)
–autoimmune degeneration ANS centrally
Adrenergics in sympathetic deficiency
- what do they do?
- which do we use?
Used to correct postural hypotension, urinary incontience, and retrograde ejaculation
Midodrine
- -alpha 1 agonist
- -give early in the day to avoid nocturnal hypertension
Sympathomimetics as cardiac stimulants
- when?
- which?
Use in AV block to prevent loss of consciousness
- -“Stokes Adams” syndrome
- -some pts alternate b/t 2nd and 3rd degree block
- -definitive tx is pacements
Use after bypass surgery
IV epinephrine, isoproterenol, dobutamine, dopamine
Indirect-acting sympathomimetics
- -Tyramine in some cheese, sausage
- -Dopamine
- -Pseudoephedrine, ephedrine
Use NE uptake system, get into nerve end and cause some NE release
