Neuro Pharmacology
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- Which type of chronic pain is characterized by a poor correlation between tissue pathology and pain?
- Chronic Non-Cancer Pain
- What type of pain is usually cutaneous or superficial?
- Somatic
- What type of pain is deep, dull, and poorly localized?
- Visceral
- What is the quality of neuropathic pain?
- Burning or dysesthetic
- Neuropathic pain results from damage to what?
- A peripheral nerve
- Where do fast and slow pain fibers synapse?
- On second-order neurons in the dorsal horn of the spinal cord
- Where do 2nd order pain neurons in the spinal cord project?
- Medulla and/or thalamus
- What is the basic mechanism of local anesthetics?
- Blockade of voltage-gated Na⁺ channels
- What are the two important features common to both amide and ester forms of local anesthetics?
-
1. Hyprophilic amine and hypdrophobic aromatic moiety
2. The amine can be protonated, with pKa of 7.5-9.0 - Which form of a local anesthetic, the charged or uncharged, is more membrane-permeable?
- The uncharged
- Which form of a local anesthetic, the charged or uncharged, is a better blocker?
- The charged
- What is the function and significance, in terms of local anesthetics, of the selectivity filter on a voltage-gated Na⁺ channel?
-
It allows entry of only Naâº, Hâ‚‚O, and H⺠into the channel
The anesthetic molecules must diffuse through the cell membrane and reach their binding sites from inside the cell - True of False: Only the charged forms of local anesthetics can bind their receptor sites inside the Na⁺ channel.
-
False
(charged binds better than free base, but free base can still bind) - Which pain fibers are blocked at lower concentrations of local anesthetics?
- Small, unmyelinated (C fibers)
- Which type of nerve fibers (touch, pain, temperature, motor, proprioception, etc) are blocked at the highest concentrations (i.e. last)?
- Touch, motor, proprioception (Aδ)
- What effect does inflamed tissue have on the local anesthetics?
-
⬢ Inflamed tissue has lower extracellular pH
⬢ More drug is protonated (extracellular), so membrane diffusion is inhibited
⬢ Block of inflamed tissue is slower than normal - How are local anesthetics generally marketed/formulated?
- As hydrochloride salts
- Why does injection of local anesthetic hydrochloride solutions "sting"?
- Because of the acidity of the solutions
- How much unchanged local anesthetic is found in urine?
- Very little, if any
- How are ester LAs and amide LAs metabolized?
-
Ester LAs = hydrolysis by plasma ChE
Amide LAs = hydrolysis by liver microsomal esterase - Which type of local anesthetics is rapidly degraded in blood by plasma cholinesterases?
- Ester LAs
- What are the cardiovascular effects of cocaine?
-
Blocks NE uptake (vasoconstriction and HTN)
Increased HR - What is the relationship between blood solubility and induction rate for general inhaled anesthetics?
- Inverse
- Which inhaled anesthetic will have a faster rise in arterial tension, one with a low blood/gas partition coefficient (B/G) or one with a high B/G?
- Low (poorly soluble)
- What effect can mechanical hyperventilation have on in inhaled anesthetics?
- It can increase the rate of anesthesia onset
- Does pulmonary blood flow rate have a direct or inverse relationship with induction rate?
- Inverse
- What effect will heart failure have on the administration of inhaled anesthetics?
- It will increase the rate of induction
- What drug should be administered with extreme caution with halothane only (is OK with other inhaled anesthetics) and why?
-
Epinephrine
Halothane uniquely sensitizes myocardium to dysrhythmias induced by catecholamines - What is the major route of elimination for inhaled anesthetics?
- Exhalation
- For which inhaled anesthetic is liver metabolism a significant process and important consideration due to the risk of severe hepatitis post-anesthesia?
- Halothane
- For which inhaled anesthetic is liver and renal metabolism a significant process and important consideration due to the risk of nephrotoxicity?
-
Methoxyflurane
(metabolism releases fluoride ions) - What type of toxicity is a unique risk of Nâ‚‚O and why?
-
Hematotoxicity
Nâ‚‚O oxidizes B12 - Which inhaled anesthetic can cause malignant hyperthermia and what is the treatment should this develop?
-
Halothane
Dantrolene - Why can Nâ‚‚O not be used alone as an inhaled anesthetic?
- 100% N₂O ≠1.0 MAC
- What three barbiturates are often coadministered with inhaled anesthetics and what is their benefit?
-
Thiopental
Methohexital
Thiamylal
Ultra-short acting - unconsciousness in ~30 seconds - What is the advantage of propofol over barbiturates?
- Recovery is even faster
- What is a risk with propofol that limits its use in some situations?
- Marked drop in systemic blood pressure
- What drug can be administered with inhaled anesthetics instead of propofol in patients with cardivascular disease?
- Etomidate
- What drug is valued in general anesthesia because it causes anterograde amnesia?
- Benzodiazepines (Midaxolam)
- What two factors limit the use of ketamine?
-
1. Cardiovascular stimulant actions (but helps with pts in cardiovascular shock)
2. Postoperative psychomimetic reactions (give with a benzodiazepine) - What is the state induced by ketamine?
-
Dissociative amnesia
(sedation, analgesia, amnesia, disconnection from surroundings) - What is the mechanism of action of ketamine?
- NMDA blockade
- What are the primary analgesics used during anesthesia?
- Opioids
- Which opioid carries an FDA block box warning and for what?
-
Droperidol
Prolongation of QTc interval, leading to cardiac arrhythmias - What is the general (not molecular) mechanism of inhaled anesthetics?
- Disruption of normal neuronal function by increased inhibitory and decreased excitatory synaptic transmission
- What is the gold-standard treatment for Parkinson's disease?
- Levodopa
- Why does levodopa lose its efficacy over time?
- Because of continued neurodegeneration (loss of synapses)
- Why do other drugs still work once levodopa is no longer beneficial in treating a patient with Parkinson's Disease?
- Because the dopamine receptors are still present and can be activated directly
- What symptom is the result of an excess of levodopa?
- Dyskinesia
- Are anti-muscarinics useful in the treatment of Parkinson's disease?
- No
- What is entacapone?
-
COMT inhibitor
(used with levodopa in treatment of PD) - What is carbidopa?
-
Decarboxylase inhibitor
(used with levodopa in treatment of PD) - Selective dopamine agonists used in the treatment of Parkinson's Disease target which dopamine receptors?
-
Dâ‚‚-like Dopamine Receptors
(D₂, D₃, and D₄) - In most cases, antiphsychotic selections are made based on what?
- Side effect profile
- Dystonic reaction responds rapidly to what treatment?
- Anticholinergic drugs (IM or IV)
- What drugs work to treat APD-induced parkinsonism?
- Antimuscarinics
- Akathisia resulting from APDs can be treated how?
-
Change of dose, drug, anti-EPS drugs
Propanolol
Lorazepam - What is the nature of the relationship between the log dose and log affinity of the typical antipsychotics?
- Linear
- What is the treatment for tardive dyskinesia caused by typical antipsychotics?
-
Sometimes responds to change of dose/medication
(Often acutely worsens with dose reduction) - What is the treatment for neuroleptic malignant syndrome caused by typical antipsychotics?
- Stop APD and Hospitalize
- What are the acute side effects of typical antipsychotic drugs? (4)
-
1. Sedation (due to histamine receptor blockade)
2. Anticholinergic (low potency = greater side-effct)
3. Orthostatic hypotension (due to α1-adrenergic blockade)
4. EPS - What are the side effects due to ACh blockade by typical antipsychotics?
-
Dry mouth
Constipation
Urinary retention
Blurry vision
Tachycardia -
Do low potency typical antipsychotics have a greater or lesser degree of side effects than high potency ones in regards to:
1. Sedation/anticholinergic
2. Hypotension (alpha-1 blockade)
3. EPS -
1. Sedation/Anti-Cholinergic = Greater (potency inversely related)
2. Hypotension = Greater (potency inversly related)
3. EPS = Lesser (potency directly related) - Is thioridazine a high, low, or medium potency typical antipsychotic?
- Low
- Is perphenazine a high, low, or medium potency typical antipsychotic?
- Medium
- Is haloperidol a high, low, or medium potency typical antipsychotic?
- High
- Which 5-HT receptor, in particular, do atypical antipsychotics have a high affinity for?
- 5-HT2A
- What two things do clozapine carry a special FDA approval for?
-
1. Tretment resistant patients
2. Reducing risk of suicide in schizophrenia and schizoaffective disorder - Which two antipsychotics have the greatest effect on QTc?
-
Thioridazine
Ziprasidone - For which patients should two AEDs be considered?
- Those that have failed different AEDs as monotherapy
- What are the four primary/general mechanisms of AEDs?
-
1. Block Na currents
2. Enhance GABA-mediated Cl currents
3. Block T-calcium currents
4. Block glutamate-mediated currents - What is the rate limiting step in the production of eicosanoids?
- Release of AA by phospholipase A2
- What is the cellular location and activation state of COX?
-
Intracellular membrane-bound enzyme
Constitutively active - What is the cellular location and activation state of lipoxygenases?
-
Soluble cytoplasmic enzymes
Migrate to cell membrane upon cell activation - What effect do leukotrienes have on inflammation?
- Monocyte and granulocyte chemotaxis
- What are the effects of prostaglandins and leukotrienes on clotting?
-
Thromboxanes activate platelets
Prostacyclins oppose clotting of platelets - Which AA derivatives constrict airway smooth muscle?
- Cysteinyl LTs
- Where are COX2 enzymes found?
- Inflammatory cells such as macrophages
- How do NSAIDS exert their antipyretic effect?
- By blocking hypothalamic prostaglandin production