Pharmacology pt 3 Flashcards
______ has the shortest DOA of the BDZ
flumazenil
- 0.7-1.3 hrs
- concern for “recrudescence” of sedation from benzos
flumazenil MOA
benzodiazepine antagonist
- partial agonist
Elimination half-life of: Diazepam Midazolam Alprazolam Lorazepam Temazepam Flumazenil
Diazepam: 20-50 hrs Midazolam: 2 hours Alprazolam: 5-25 hours Lorazepam: 10-20 hrs Temazepam: 10 hrs
Flumazenil: 0.7-1.3 hrs
Desflurane degradation in the presence of desiccated carbon dioxide absorbent results in production of _____
carbon monoxide and heat
- desflurane produces most CO
- sevo produces most heat
Order of fluoride production for volatile anesthetics?
- theoretical risk of nephrotoxicity
Methoxyflurane»_space; sevoflurane > isoflurane > desflurane
Compound A is produced from which volatile anesthetic?
Sevoflurane
ED95 dose for: Rocuronium Cisatracurium Vecuronium Pancuronium
Rocuronium: 0.3
Cisatracurium: 0.04
Vecuronium: 0.04
Pancuronium: 0.06
Potency of neuromuscular blockers is best described by their ____
ED95
Effect of dexmedetomidine on BP over time
Biphasic response bc alpha 2 receptors are located in 2 diff places
- initial dose: stimulates peripheral alpha-2 -> Inc in BP, decrease in HR and CO after 3 min
- returns to baseline
- Over the next hour: stimulates central alpha 2 -> reduce sympathetic tone, inc parasympathetic outflow -> slow decline in BP, inc in HR
MOA?
Onset of action ?
Duration of action?
- Cimetidine
- Ranitidine
- Famotidine
H2 receptor antagonist
- raises gastric pH
- Cimetidine (older):
- 1-1.5 hrs
- 3 hours - Ranitidine:
- 1 hrs
- 9-10 hours - Famotidine: 1 hrs
- 1 hr
- 10-12 hours
Which reversal agent is pulmonary edema seen in? (not muscle relaxant)
naloxone
- esp in large doses
CCBs to a naive pt will affect depolarizing and nondepolarizing NMBs how?
Mild augmentation to both
- CCBs prevent Ca2+ from crossing membrane -> less excitation-contraction
*CCBs to chronic users have very little effect
Why is meperidine falling out of favor?
Wide side effect profile and long half-life
*Libby Zion: the reason we have resident work hour limits
How does meperidine decrease shivering?
through the k opioid receptor (not mu)
*although it still affects mu
Major subtypes of opioid receptors
mu, kappa, delta
Actions of:
Mu1 receptor
Mu2 receptor
Mu1 receptor
- analgesia
- physical dependence
Mu2 receptor
- respiratory depression
- miosis
- euphoria
- dec GI motility
- physical dependence
Actions of:
Kappa receptor
delta receptor
Kappa receptor
- analgesia
- dysphoria
- sedation
- miosis
- inhibit ADH
delta receptor
- analgesia
- physical dependence
- antidepressant
Nalbuphine MOA
Kappa agonist
Mu antagonist
What is morphine metabolized to? What is the active metabolite?
M3G and M6G
M6G is active metabolite
What is the only opioid that is also associated with inc in HR?
meperidine
- structurally similar to atropine
Liver blood flow dependent elimination is characteristic of _____ order kinetics
first
What is first order kinetics
drug elimination is proportional to drug concentration
- exponential
What is zero order kinetics?
enzymes involved in drug metabolism are at a max capacity
- drug metabolism is INDEPENDENT of drug [ ] bx enzymes are saturated
- rate of elimination of constant amt of medication is removed over time
- linear
Drugs that follow zero-order kinetics
(- drug metabolism is INDEPENDENT of drug [ ] bx enzymes are saturated
- rate of elimination of constant amt of medication is removed over time)
THE PAW
Theophylline Heparin Ethanol Phenytoin ASA Warfarin
Which induction agent works primarily by blocking glutamate?
Ketamine
- NMDA receptor antagonist
- NMDA r are a class of excitatory glutamate receptor
Which induction agent INDIRECTLY potentiates GABA receptors?
Ketamine
*etomidate, midaz, prop all potentiate via direct action
Succinylcholine effect on:
Upper esophageal sphincter tone
Intragastric pressure
Lower esophageal sphincter tone
Upper esophageal sphincter tone:
- decrease
Intragastric pressure
- increase
Lower esophageal sphincter tone
- increase (greater than intragastric pressure so NO inc risk of aspiration)
How does adding epi to LA work?
Prolongs duration of effect by decreasing local blood flow, LA stays in area of injection.
*does NOT change block onset time
is the active form of LA ionized (charged) or unionized (uncharged)?
ionized
*unionized pass through lipid membrane and reach targets easier than ionized molecules
The onset of action of LA is primarily a result of _____
lipid solubility
- pass thru membrane and reach site of action
pKa
- aka ionization of drug
- lower pKa = more unionized forms = faster onset (pass through lipid membrane and reach targets easier than ionized molecules)
- higher pKa = more ionized forms = slower onset
Addition of what to LA speeds the onset of action?
bicarb - raises the pH of soln -> more unionized fraction -> faster onset (pass through lipid membrane and reach targets easier than ionized molecules)
greater concentration
- ie. chloroprocaine pka 9 would predictably have slow onset, but actually
What is the MOA of ACEi?
catalyzes degradation of bradykinin ->
Arachidonic acid and nitric oxide
Inhibit the vasoconstrictive and sodium retentive properties of ATII (via aldosterone stim)
Promote the vasodilatory and natriuretic properties of bradykinin
____ cleaves angiotensinogen to angiotensin I
_____ then cleaves angiotensin I to angiotensin II
Renin
ACE
*ACEi block this conversion step
_____ release is the final step in the RAS pathway, which is stimulated by ___
Aldosterone
- promotes sodium and water retention in kidney via activation of Na-K pump in distal tubule
ATII
Cyclopentolate MOA and use?
Topical anticholinergic drug to induce mydriasis for ocular procedures
- at risk for anticholinergic toxicity
- dysarthria, tachycardia, psychosis, convulsions, disorientation
Acetylcholine effect on eyes
miosis
- facilitates flow of aqueous humor
- lowers IOP
Echothiophate MOA and use?
Anticholinesterase (inc ACh)
Treats refractory glaucoma by causing MIOSIS
*remember ACh effects on eyes:
miosis
- facilitates flow of aqueous humor
- lowers IOP
Timolol MOA and use
nonselective BB
glaucoma tx
Normally, the rate of rise of FA/FI is related to solubility or the blood:gas coefficient.
What explains why nitrous oxide has more rapid rise of FA/FI than desflurane
concentration effect
- high [ ] anesthetic (ie. 70% nitrous oxide) increases rate of induction
- nitrous oxide is the only gas that can demonstrate [ ] effect
What is the blood:gas coefficient for nitrous oxide and desflurane
Nitrous oxide: 0,47
Desflurane: 0.42
*the blood:gas coefficient is often the most important factor in rise of FA/FI, which is related to the speed of inhalational induction
*the________ is often the most important factor in rise of FA/FI, which is related to the speed of inhalational induction.
In order of most to least, what is the solubility of commonly used inhaled anesthetics
blood:gas coefficient
desflurane > nitrous oxide > sevoflurane > isoflurane
The _______ is a measure of lipophilicity. It is related to anesthetic potency and MAC
Oil:gas coefficient
- higher the coefficient, the lower the MAC
- ie: isoflurane has o:g of 99, and MAC of 1
- desflurane has o:g of 19 and MAC of 6
What are the 4 potassium sparring diuretics?
- Spironolactone
- Triamterene
- Amiloride
- Eplerenone
- block Na reab in collecting tubule, increasing K reab
*The K STAEs
Hyperkalemia sx on EKG other than peaked T waves
- shortened QT interval
- widening QRS
3, PR prolongation
- similar to hypermagnesemia
How much nalbuphine is useful to tx pruritus in neuraxial anesthesia?
5-10mg nalbuphine
What is mannitol?
A sugar alcohol that acts as an osmotic diuretic that is freely filtered at the glomerulus with poor reuptake back into the vasculature
*similar to hyperglycemia
What is Atrial Natriuretic peptide (ANP)?
released in response to atrial stretch (gen d/t volume overload)
- induces diuresis via natriuresis (not osmotic effect)
Prostaglandins affect fluid balance how?
They oppose ADH and RAAS
- facilitates a diuretic and natriuretic effect
- renal afferent arteriolar dilation
Mannitol is an osmotic diuretic, which pt population is it contraindicated in?
CHF - d.t initial increase in intravascular volume
- use furosemide for diuresis in these pts instead
Terbutaline MOA
- causes (hyper/hypo)kalemia
beta2 agonist
- hypokalemia: temp intracellular shift
What is a phase 2 block?
occurs when succinylcholine remains on ACh receptors
- keeps receptors activated and in OPEN position
- occurs after prolonged admin of succinylcholine or single dose > 4mg/kg
Heparin has a 1:1 anti-Xa:IIa ratio.
What does LMWH have?
Increased anti-Xa:IIa ratio.
- shorter chain length does not inactivate thrombin to a significant degree, but it does inactivate Xa
LMWH is cleared (hepatically/renally)
renally,
- Smaller fragments of heparin in LMWH binds to macrophages in liver less -> cleared renally -> leading to longer plasma half lives and effective once daily regimen
Why is LMWH less likely to induce HIT?
smaller fragments of heparin in LMWH binds to platelets less
______ drugs prevent platelet activation and aggregation (clot prophylaxis)
_______ reduce fibrin formation (treatment of acute thrombi)
antiplatelet
Anticoagulant
4 Classes of antiplatelet drugs
- prevent platelet activation and aggregation (clot prophylaxis)
- Irreversible COX inhibitors
- ASA - ADP r inhibitors
- Clopidogrel
- Prasugrel
- Ticlopidine
- Ticagrelor - PDE inhibitors
- Cilostazol
4, G IIb-IIIa inhibitors
- abciximab
- eptifibatide
- tirofiban
5 Classes of anticoagulant drugs
- reduce fibrin formation (treatment of acute thrombi)
- Antithrombin III activators
- Heparin
- LMWH - Heparin like factor Xa inhibitors
- fondaparinux - Direct factor Xa inhibitors
- rivaroxaban
- apixaban - Direct thrombin inhibitors
- bivalrudin
- hirudin
- argatroban
- dabigatran - Vit K antagonist
- Warfarin
Which antiplatelet drug has the longest antiplatelet effect?
Ticlopidine (10-14 days)
- ADP receptor inhibitor
- drug works for several days after admin
- impairs platelets for duration of its lifespan
- needs to be stopped 2 weeks b4 surgery
Which anticoagulant drug has the longest effect?
warfarin/dabigatran
- 2-7 days
Phenytoin and Lidocaine are class Ib antiarrhythmic, that shortens which phase of the cardiac action potential?
Phase 0
- binds to VG sodium channels to terminate ventricular arrhythmias (in the past)
Drugs affecting Cardiac action potential:
- Class 1 (Na channel blocker, Phase 0)
1a: Quinidine, Procainamide
1b: Lidocaine, Phenytoin
1c: Flecainide, Propafenone