Pharmacology Flashcards
Why are obese patients relatively resistant to succinylcholine?
increased butyrylcholinesterase (pseudocholinesterase) levels
Accumulation of which narcotic metabolites is of concern in patients with renal failure?
- hydromorphone-3-glucuronide -> neuro-excitation and cognitive impairment
- morphine-6-glucuronide -> active metabolite
- normeperidine -> seizures
Which drugs are metabolized by butyrylcholinesterase (pseudocholinesterase)?
succinylcholine
mivacurium
physostigmine
organophosphates
Which drugs are metabolized by plasma esterases?
remifentanil
esmolol
ester local anesthetics
succinylcholine
atracurium (also Hoffman elimination)
etomidate (also liver metabolism)
How is lorazepam metabolized?
glucuronidation in the liver (also oxazepam and temazepam)
* no active metabolites *
What factors influence myalgias following succinylcholinc administration?
more common in women
more common with minor surgery
more common with early ambulation
less common in pregnant vs. non-pregnant women
less common in children and elderly patients
less common with greater muscle tone
What metabolic functions are served by the lung?
- conversion of angiotensin I to angiotensin II
- inactivation of bradykinin (by ACE)
- inactivation/uptake of norepinephrine; serotonin; and prostaglandins E1, E2, and F2alpha
How long is a time constant?
The time it would take an exponential process to be complete if the initial rate had continued.
1 time constant: 63% complete
2 time contants: 87.5% complete
3 time constants: 95% complete
What is ED95 in the context of muscle relaxants?
dose needed to decrease twitch height by 95%
What drugs exhibit zero-order kinetics?
ethanol
thiopental
How does renal failure affect volume of distribution? How does this affect drug dosing?
- increases volume of distribution due to decreased plasma binding proteins
- should increase loading dose and dosing interval
How are midazolam and diazepam metabolized?
cytochrome P450 oxidation in the liver
Besides IV administration, which route provides highest plasma levels of midazolam?
intramuscular
Where are opioid receptors predominantly located?
- periaqueductal gray (brainstem)
- amygdala
- corpus striatum
- hypothalamus
- substantia gelatinosa
Which serum proteins bind most drugs?
albumin binds acidic drugs
alpha-1 glycoprotein binds basic drugs
Which opioid side effects are associated with Mu 1 receptors? Mu 2 receptors? Kappa receptors? Delta and sigma receptors?
Mu 1: urinary retention and euphoria
Mu 2: constipation, physical dependence, and hypoventilation
Kappa: dysphoria and hallucinations
Delta and sigma: dysphoria
Which opioids cause significant histamine release?
morphine and meperidine - can cause bronchospasm
Which opioid can cause tachycardia?
meperidine - similar structure to atropine
Which opioid effects do not show tolerance?
miosis and constipation
How is remifentanil metabolism different between adults and infants?
faster in infants
What are the equivalent IV and PO doses of morphine? Hydromorphone?
morphine: 10 mg IV = 30 mg oral
hydromorphone: 1 mg IV = 5 mg oral
Which narcotic has local anesthetic activity?
meperidine
Which narcotic effects are reversed by naloxone? Which are not?
Reversed: respiratory depression, analgesia, pruritis
Not reversed: constipation, nausea/vomitting, muscle rigidity
What is the primary organ for redistribution of propofol when it residtributes from the brain?
skeletal muscle
What are the features of propofol infusion syndrome?
metabolic acidosis
rhabdomyolysis
hyperkalemia
bradycardia
What are some common indications for ketamine?
cardiac tamponade (increased HR and SVR)
bronchial asthma (bronchodilatory)
tetralogy of Fallot
hypothyroidism
What drugs are contraindicated in acute intermittent porphyria?
barbiturates
etomidate
hydralazine
steroids
OCPs
alpha-methyldopa
chlordiazepoxide
nitrazepam
flunitazepam
How much will nitrous oxide expand a pneumothorax?
50% N2O: 2x
66% N2O: 3x
75% N2O: 4x
How much of each inhaled anesthetic is metabolized by the body rather than exhaled?
halothane: 20%
sevoflurane/enflurane: 2%
isoflurane: 0.2%
desflurane: 0.02%
What are the OSHA guideline for exposure limits to inhaled anesthetics?
N2O: 25 ppm/hour
all others: 2 ppm/hour
What is the Overton-Mayer theory?
correlation between lipid solubility of anesthetic agents and their potency
What factors increase MAC?
neonates
chronic alcoholism
acute amphetamine use
MAOIs, cocaine
hyperthermia
hypernatremia
What factors do NOT affect MAC?
duration of anesthesia
gender
pH or PaCO2
hypo/hyperthyroidism
What factors decrease MAC?
old age
pregnancy
hyperbaric chamber (nitrogen narcosis)
chronic amphetamine use
acute alcohol use
What factors increase carbon monoxide production in the anesthesia circuit?
desflurane
low gas flows
dry or warm absorbent
baralyme > sodalyme
What is the order of onset and recovery of neuromuscular blockade in different muscle groups?
diaphragm > laryngeal muscles > adductor pollicis
How do antibiotics affect neuromuscular blockade?
All antibiotics potentiate blockade, EXCEPT:
penicillin
cepharlosporins
erythromycin
What is the best clinical test of adequate neuromuscular blockade?
neonates: sustained leg lift
adults: masseter muscle tone
How is the dosing of rocuronium and neostigmine affected by renal failure?
clearance of both is prolonged, dose should be reduced
What is the significance of dibucaine number?
butyrlcholinesterase alleles:
80: WT
40-60: heterozygous
20: mutant
How much does succinylcholine increase postassium levels in a normal patient?
0.5 mEq/L
Which electrolyte abnormalities prolong neuromuscular blockade?
“Louis CK”
hypocalcemia
hypokalemia
“Hymen”
hypermagnesemia
hypernatremia
Which drugs prolong the duration of action of both depolarizing and non-depolarizing muscle relaxants?
lithium
magnesium
Which drugs inhibit butyrlcholinesterase and prolong the duration of action of succinylcholine?
metoclopramide
pancuronium and mivacurium
acetylcholinesterase inhibitors
nitrogen mustard, trimataphan, and echothiophate
How do ester local anesthetics interact with acetylcholinesterase inhibitors (neostigmine, pyridostigmine)?
ester local anesthetics potentiate acetylcholinesterase inhibitors
What properties affect onset time of local anesthetics?
pKa (lower is faster)
concentration
Which properties affect the duration of action of local anesthetics?
protein binding (stronger is longer)
Which properties affect the potency of local anesthetics?
lipid solubility
Which local anesthetics can cause methemoglobinemia?
benzocaine and prilocaine
Which drugs are contraindicated in G6PD deficiency?
nitrofurantoin and sulfa
isoniazid and dapsone
methylene blue
anti-malarials
Are patients with G6PD deficiency more or less susceptible to methemoglobinemia?
more susceptible
What are the properties of tumescent lidocaine used for liposuction?
concentration: 0.025-0.1%
dose: 35-55 mg/kg
time to peak concentration: 12-14 h
epinephrine: 1:1,000,000
What are the target receptors of metoclopramide?
D2 antagonist
5HT3 antagonist
5HT4 agonist
What are the clinically used ß2 agonists?
albuterol
terbutaline
ritodrine
What are the common side effects of ß2 agonists?
hypotension
tachycardia
hyperglycemia
pulmonary edema
hypokalemia
What are the clinical uses of glucagon?
hypoglycemia
reducing biliary spasm
beta-blocker overdose
What are the acute and chronic side effects of amiodarone?
acute: hypotension, QT prolongation, torsades
chronic: pulmonary fibrosis, hypo/hyperthyroidism
What are the clinical features of digoxin toxicity?
arrhythmias (AV block, PVCs, VT)
nausea & vomitting
xanthopsia
What are the indicated treatments for digoxin toxicity?
Digibind
treatment of hyperkalemia (EXCEPT CALCIUM)
magnesium (EXCEPT WITH AV BLOCK)
lidocaine to treat ventricular arrhythmias
What are the contraindicated treatments for digoxin toxicity?
calcium
procainamide
cardioversion
What are the indicated uses for ACEIs/ARBs?
systolic heart failure
anterior MI w/ low EF
diabetic nephropathy
When are ACEIs/ARBs contraindicated?
pregnancy
bilateral renal artery stenosis
h/o angioedema
Which supplements can cause mild platelet dysfunction?
ginseng
garlic
ginko biloba
