Pharm Autanomic II (8)

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  1. adrenergic receptors (adrenoceptors)
    • a class of G protein-coupled receptors that are targets of the catecholamines, especially norepinephrine & epinephrine
    • are found on many cells
    • the binding of a catecholamine to the receptor generally stimulates the sympathetic nervous system (SNS)

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  2. What are the two types of adrenergic receptors?
    • 1. alpha (α) receptors
    • 2. beta (β) receptors
    • each can be further divided into subtypes found throughout the body but often concentrated in a particular area
  3. α1 Adrenergic Receptors
    • found most abundantly in blood vessels
    • stimulation usually CONSTRICTS vessels via Ca2+ mobilization
    • α1 activation also results in elevated BP [via blood vessel constriction]
  4. α2 Adrenergic Receptors
    • located primarily on the surface of PRE-synaptic neurons in the brain
    • when stimulated they SUPPRESS the release of norepinephrine from pre-synaptic terminals by inhibiting adenylate cyclase
    • *are sometimes referred to as auto-inhibitory receptors
    • [alpha-2 will auto-inhibit YOU!]
  5. β1 Adrenergic Receptors
    • primarily located in the heart
    • when stimulated they INCREASE heart rate & contractility by activating adenylate cyclase
  6. What does blocking β1 receptors do?
    • reduces heart rate & contractility
    • (opposite of what activating them does)
    • this reduction on the workload of the heart is desirable in patients who have suffered a myocardial infarction or have certain types of heart failure
  7. β2 Adrenergic Receptors
    • located primarily in the lungs
    • when stimulated they relax smooth muscles & dilate the bronchi (bronchodilation) by activating adenylate cyclase
    • (are also found on the brain vasculature where they can produce cause vasodilation & contribute to the pathogenesis of migraines
    • in comparison to α1 receptor stimulation however, their effect on the peripheral vasculature is relatively WEAK)
  8. β-blockers
    • medications that reduce heart rate & contractility by blocking sympathetic stimulation of β adrenergic receptors
    • given to patients who have suffered a myocardial infarction or have certain types of heart failure
    • eg. propranolol
  9. Propranolol
    • a NON-selective β-blocker that blocks both β1 & β2 receptors to roughly the same degree
    • a sympatholytic drug used to treat hypertension
    • blocking β2 receptors results in the unwanted side effects of bronchoconstriction
    • *non-specific β-blockers like propranolol used for post-myocardial infarction are contra-indicated in ASTHMATICS
  10. For what patient population is using non-selective β-blockers problematic?
    • those with underlying pulmonary disorders
    • for such cases beta-blockers that specifically target β1 receptors (β1 selective blockers) should be used
    • eg. Atenolol, Metoprolol
  11. What are two off-label uses of beta-blockers?
    • 1. to manage the somatic symptoms of anxiety disorders (eg. social phobias, performance anxiety); have an anxiolytic effect
    • *unlike psychoactive medications commonly used for anxiety disorders (eg. benzodiazepines), β-blockers improve somatic symptoms WITHOUT impairing cognition & memory
    • 2. prophylaxis of migraines
    • non-selective beta-blockers tend to work best but selective blockers can also be helpful
  12. The Effects of Sympathetic & Parasympathetic Activation on the Cardiovascular System
    • SNS (NE, EPI)    PSNS (ACh)
    • Heart Rate             ↑↑ via β1        ↓↓
    • Force of Contraction ↑↑ via β1        ↓
    • Metabolism              ↑ via β1
    • O2 Consumption      ↑↑ via β1        ↓
    • BV Constriction        ↑↑ via α1
    • BV Dilation (Brain)    ↑ via β2
    • BP                            ↑↑              ↓

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  13. What are the effects of β-blockers on bronchial function?
  14. What are the effects of β-blockers on cardiac function?
    decreased contractility & reduced heart rate
  15. Sympathomimetic Drugs
    • mimic the effects of sympathetic nervous system neurotransmitters such as catecholamsines (NE, EPI)
    • they're adrenergic receptor agonists
    • treat cardiac arrests, low BP
    • [mimetic think mimic, they mimic NTs]

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  16. Albuterol
    • a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm in asthma & chronic obstructive pulmonary disease
    • (terbutaline is another β2-adrenergic receptor agonist used off-label to delay pre-term labor!)
  17. Clonidine
    • an α2-adrenergic receptor agonist that binds to α2 receptors & inhibits the production of norepinephrine from pre-synaptic terminals
    • because norepinephrine causes vasoconstriction, clonidine inhibiting its release is used to treat hypertension (high blood pressure)
  18. Isoproterenol
    • a non-selective β1 & β2 adrenergic receptor agonist that's structurally similar to adrenaline used to treat cardiac arrest
    • if a β-receptor agonist might overexcite a weak heart, dopamine can instead be given by IV to more gently stimulate a not-beating heart
  19. Sympatholytic Drugs
    • medication that inhibits the post-ganglionic functioning of the sympathetic nervous system (SNS)
    • they're adrenergic receptor antagonists
    • eg. antihypertensives

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  20. Atenolol
    • a β1 receptor antagonist given after a MI
    • it slows down the heart & reduces its workload
    • replaced propranolol for hypertension treatment b/c unlike propranolol, atenolol doesn't pass through the BBB, reducing CNS side effects
  21. Labetalol
    • a mixed α1 & β2 adrenergic antagonist used to treat high blood pressure [hypertension]
    • it binds more strongly to α1 receptors, inhibiting their activation & therefore preventing the constriction of blood vessels
  22. What drugs affect the parasympathetic nervous system to treat hypertension?
    • NONE - all hypertensive medications work by modifying SNS receptors
    • methyldopa interferes with NT production & release
    • clonidine suppresses NE release
    • prazosin antagonizes receptor response to NTs
    • other drugs commonly used include diuretics, converting enzyme (ACE) inhibitors, angiotensin receptor antagonists, & certain calcium channel blockers

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  23. Serotonin
    • located primarily in the brain & in enterochromaffin cells in the GI tract
    • it constricts bronchial & gastrointestinal smooth muscles
    • it constricts extra & intracranial vessels causing migraines
    • it DILATES skeletal muscle blood vessels & is associated with flushing (eg. carcinoid syndrome)
    • it stimulates sensory nerve endings
  24. How is serotonin degraded?
    by MAO (monoamine oxidase), similarly to DA, NE, & EPI
  25. What are clinical conditions that involve aberrant levels of serotonin?
    • 1. Carcinoid syndrome
    • 2. Depression: associated with low levels in the CNS
    • 3. Migraines: due to cerebrovascular constriction following acute ↑ serotonin
    • 4. Flushing of the face: associated with ↑ plasma levels
    • 5. Sleep: due to increased amount in the median raphe nucleus of the pons
  26. Carcinoid Syndrome
    • the array of symptoms that occur secondary to carcinoid tumors which causes endogenous secretion of serotonin
    • characterized by flushing, hypOtension, diarrhea, & right heart failure (serotonin is inactivated in the lung & therefore does't affect the left side of the heart)
  27. How is Carcinoid Syndrome diagnosed?
    • by measuring the levels of the main metabolite of serotonin (5-HIAA) in a 24 urine collection
    • a high level of 5-HIAA is suggestive of this syndrome
  28. Antimigrane Drugs
    serotonin receptor AGonists
  29. Sumatripan (Imitrex)
    • an agonist of certain serotonin receptors (5HT1B, 5HT1D)
    • causes selective vasoconstriction of cranial blood vessels providing quick migraine relief
    • it can't be used prophylactically b/c it can precipitate a migraine (vasoconstriction often does)
    • is best avoided in patients with ischemic heart disease, stroke, & pregnancy
  30. Ergot Alkaloids
    • a compound made from fungus that grows on wet rye plants; it can mimic the action of serotonin
    • causes peripheral vasoconstriction & CNS stimulant activity (convulsive ergotism w/ hallucinations)
    • less commonly used for migraine treatment b/c their half-life = 1 week (how long hallucinations may last)
    • ergots should be avoided in patients w/ ischemic heart disease
  31. Antiemetic Drugs
    serotonin receptor ANTagonists that treat nausea & vomiting
  32. Ondansetron (Zofran)
    • an antagonist of certain serotonin receptors (5HT3)
    • blocking this receptor type leads to reduced nausea, making this drug a powerful antiemetic therapy
    • is used in patients w/ cancer to relieve nausea & vomiting associated w/ chemotherapy
    • constipation is a common side effect related to blockage of serotonin receptors in the GI tract
  33. Melatonin (O-methyl Serotonin)
    • a derivative of serotonin that helps maintain the sleep/wake cycle
    • is used for circadian rhythm disorders (jet-lag) or for trouble falling asleep
    • *newly discovered to control T17 cells
  34. Muscle Tension Headaches
    • occurs equally between men & women
    • presents as a generalized, constant pain
    • may be caused by muscle tension around the head and neck
    • most common type of primary headache
    • treated w/ acetaminophen & NSAIDs
  35. Migraines
    • present with aura (visual disturbances), peripheral neuropathy, nausea, vomiting, sonophobia, photophobia, and more severity on one side of face (hemicrania)
    • can evolve over several hours or develop suddenly
    • is seen in 3x more females than males & is more frequent during ovulation
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  36. What are the two phases of migraine headaches?
    • Phase 1: vasoconstriction of brain blood vessels prevents enough blood from getting to the brain
    • Phase 2: compensatory vasodilation of blood vessels occurs in response to the original vasoconstriction; comes w/ a severe throbbing pain
    • eventually the throbbing subsides & patients are left with a dull tension-like headache
    • *serotonin drugs could ONLY be given during phase 2 as they'd help contract overly dilated vessels; giving during phase 1 would worsen the problem
  37. How are medications for migraine treatment classified?
    based on whether they prevent phase 1 from occurring (drugs for migraine prophylaxis) or acutely relieve symptoms associated with phase 2 (drugs to abort a migraine, eg. sumatriptan)
  38. Phase 1 Migraine Treatments
    • amitriptyline, cyproheptadine (anti-H1/anti-5HT), propranolol, verapamil (prevents phase II), valproate, gabapentin, topiramate (anti-seizure)
    • anti-seizure drugs are VERY popular; it's hypothesized that phase 1 is a part of the brain having a "mini-seizure" → excessive vasoconstriction
  39. Phase 2 Migraine Treatments
    sumatriptan or ergotamine
  40. Cluster Headaches
    • presents as pain on one side of face/head with a runny nose or runny nostril
    • is seen in 2x more males than females
    • treated acutely with indomethacin or hyperbaric oxygen
    • can be preventatively treated w/ prednisone or topiramate
  41. Neuronal Plasticity
    • when stopping therapy with medications that affect NT levels or receptors discontinuation should be GRADUAL over a few weeks to allow for the base line to readjust
    • *Immediate drug removal may precipitate a crisis of the very condition you are attempting to treat
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Pharm Autanomic II (8)
2013-12-15 16:15:28
Exam 2
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