Pharmacology Flashcards
Which of the following causes resistance to neuromuscular blockade? (2012/Q23)
A. Carbamazepine
B. Cyclosporine
C. Furosemide
D. Lithium
A. Examples of drugs that can enhance nondepolarizing neuromuscular blockade include (a) volatile anesthetics, (b) aminoglycoside antibiotics, (c) local anesthetics, (d) cardiac dysrhythmic drugs, (e) diuretics, and (f) magnesium and lithium. Patients treated chronically with anticonvulsants (phenytoin, carbamazepine) are relatively resistant to some (pan, vec, roc, cis, pipe, doxa) NDMR. Cyclosporine may prolong the duration of neuromuscular blockade produced by nondepolarizing drugs. (Stoelting’s P2 p225-6)
What is true about remifentanil? (2012/Q9)
A. Accumulates in renal failure
B. Accumulates in liver disease
C. Metabolized by pseudocholinesterase
D. Context-sensitive half-life not prolonged by long infusion time
D. Remifentanil’s ester structure renders it susceptible to hydrolysis by nonspecific plasma and tissue esterases to inactive metabolites. This unique pathway of metabolism imparts (a) brevity of action, (b) precise and rapidly titratable effect due to its rapid onset and offset, (c) noncumulative effects, and (d) rapid recovery after discontinuation of its administration. In fact, the rate of decline (context-sensitive half-time) of the remifentanil plasma concentration will be nearly independent of the infusion duration. (Stoelting P2 p112-4)
Comparing dexmedetomidine to clonidine, which is true? (2012/Q27)
A. Dex has a longer duration of action
B. Dex is less specific for the alpha-2 receptor
C. Dex has dose-dependent analgesia and sedation
D. Dex promotes shivering
C. Clonidine is a centrally acting selective partial alpha-2-adrenergic agonist while dexmedetomidine is a highly selective, specific and potent alpha-2-adrenergic agonist. Clonidine has a relatively long half-time of 6 to 10 hours while dexmedetomidine has a half-time of only 2 to 3 hours and is more potent than clonidine at alpha-2 receptors. Preservative-fee clonidine administered in the epidural or subarachnoid space produces dose-dependent analgesia. Despite marked dose-dependent analgesia and sedation produced by dexmedetomidine, there is only mild depression of ventilation. Administration of clonidine 75 mcg IV stops shivering, dexmedetomidine markedly increases the range of temperatures not triggering thermoregulatory defences and also proves to be an effective treatment for shivering. (Stoelting’s P2 p340-5)
This herbal medication may act as a sedative-hypnotic by potentiating inhibitory neuro transmission of gamma-aminobutyric acid (GABA). (2012/Q36)
A. Ginkgo
B. Ginseng
C. Saw Palmetto
D. Kava
D. Valerian, kava-kava and possibly St. John’s wort may delay awakening from anesthesia by prolonging sedative effects of anesthetic drugs. Kava interacts with benzodiazepines, anesthetic drugs and alcohol. (Stoelting’s P2 p610)
All of the following diseases may be associated with a severe hyperkalemic response to administration of succinylcholine, except? (2012/Q41)
A. Duchenne Muscular Dystrophy
B. Cerebral Palsy
C. Rhabdomyolysis
D. 40% BSA burn, 4 days post-injury
B. Succinylcholine increases plasma potassium concentration by 0.5 mEq/L due to muscle depolarization and net efflux of K out of the cell. This can occur in patients with muscular dystrophy, unhealed 3rd degree burns, denervation leading to skeletal muscle atrophy, severe skeletal muscle trauma and UMN lesions. Any disease that causes proliferation of extrajunctional ACh receptors are likely to have an exaggerated response. No evidence for hyperkalemia in Parkinson’s disease, cerebral palsy, myelomeninogecele or cerebral aneurysm. (Stoelting’s P2 p220; Miller p865)
Which of the following causes a delay in the increase of Fa:Fi? (2012/Q40)
A. Increase minute ventilation
B. Shortened circuit
C. Collapsed bag
D. Dry CO2 absorbent
D. Three factors important in Fa:Fi are: (1) the volume of the external breathing system, (2) the solubility of the given agent in the rubber and plastic component of system, and (3) the gas inflow from the anesthetic machine. Uptake by soda lime is small unless the soda lime is dry, where appreciable amounts of agent may be absorbed. An increase in uptake or rebreathing lowers the Fi of a highly soluble gas more than a poorly soluble gas. (Miller p549)
How long until 90% elimination of 100 mg lidocaine IV? (2012/Q53)
A. 1.5 hours
B. 3 hours
C. 4.5 hours
D. 6 hours
D. t1/2 of lidocaine is 96 minutes. For 90% of lidocaine IV to be eliminated, it will take approximately 3.5 t1/2. 3.5 x 96 min = 5.6 hours (Stoelting’s P2 p181)
Which drug increases serum potassium levels? (2012/Q57)
A. Epinephrine
B. Salbutamol
C. Furosemide
D. Captopril
D. Side effects of captopril. Hyperkalemia is possible due to increased production of aldosterone. The risk of hyperkalemia is greatest in patients with recognized risk factors (CHF with renal insufficiency). (Stoelting’s P2 p345-7)
All are true regarding verapamil, except? (2012/Q58)
A. Contraindicated in atrial fibrillation with high ventricular rate
B. Increases orthodromic accessory pathway conduction
C. Increases cerebral blood flow more than metoprolol
D. ???
C. Verapamil use is indicated for atrial fibrillation with high ventricular rate and treatment of orthodromic accessory pathway. CCB are used intraarterially as a primary treatment for medically-refractory vasospasm. Multiple studies from the 1980-90s have shown that metroprolol does not increase cerebral blood flow. (Stoelting’s P2 p390; Miller Ch27)
Which one of the following drugs prolongs the QT interval? (2012/Q59)
A. Propofol
B. Hydromorphone
C. Droperidol
D. Rocuronium
C. Prolonged QTc syndrome is a malfunction of cardiac ion channels resulting in impaired ventricular repolarization that can lead to a characteristic polymorphic ventricular tachycardia known as torsades de pointes. This prolongation most often results from delayed ventricular repolarization, a process that is medicated by the efflux of intracellular potassium. Droperidol is capable of proloning the QTc interval on the ECG in some patients. Although the QTc prolongation effect peaks 2 to 3 minutes following IV administration, the effects may persist for several hours. Unlike sevoflurane, propofol does not prolong the QTc interval on ECG. (Stoelting’s P2 p415-6)
What is the effect of isoflurane on ventilation? (2012/Q60)
A. Increases RR and increases TV
B. Increases RR and decreases TV
C. Decreases RR and increases TV
D. Decreases RR and decreases TV
B. Inhaled anesthetics, except isoflurane, produce dose-dependent increases in the frequency of breathing. Isoflurane behaves similarly upt o a dose of 1 MAC; at concentration >1 MAC, isoflurane does not produce a further increase in frequency of breathing. TV
What is the clearance of the drug if steady state concentration of 8 mg/L is maintained with infusion of 5 mg/min? (2012/Q62)
A. 40 min
B. 120 min
C. 450 min
D. 600 min
D. Following a bolus, it takes 1 half-life to reduce the concentrations by half, and during an infusion, it takes 1 half-life to increase the concentration halfway to steady state. By 4 to 5 half-lives, we typically consider the patient to be at steady state. The context-sensitive half-time is defined as the time required for the drug concentration of the plasma to decrease by 50%, where the context is the duration of the infusion.
Regarding myalgia with succinylcholine: (2012/Q63)
A. May get myoglobinuria
B. Correlate with amount of fasisculations
C. More in men
D. ???
A. The incidence of muscle pain after succinylcholine varies from 0.2 to 89%. It occurs more frequently in after minor surgery, especially in women (C) and in ambulatory rather than bedridden patients. The damage to muscle has been substantiated by finding myoglobinuria (A) and increases in serum creatine kinase after SCh administration. Prior administration of a small dose of NDMB clearly prevents SCh-related fasciculations. However, the efficacy of this approach in preventing muscle pain is questionable. (Miller p866; P2 p221)
Regarding the clearance of drugs with a low hepatic extraction ratio, which is true? (2012/Q77)
A. Insensitive to hepatic flow
B. Increases with mild liver disease
C. …something about free fraction of the drug
D. …something about relationship with intrinsic metabolic capacity (Vm)
A. Hepatic clearance of a drug is the product of hepatic blood flow and the hepatic extraction ratio. If hepatic extraction ratio is high (>0.7), the clearance of drug will depend on hepatic blood flow, whereas changes in enzyme activity will have minimal influence. High hepatic extraction ratio results in perfusion-dependent elimination. If hepatic extraction ratio is
A 12- year-old boy weighing 40 kg has a 40 mcg/kg/h continuous infusion of morphine for pain control after hand surgery. What is the most appropriate oral conversion? (2012/Q78)
A. 20 mg PO q8h
B. 20 mg PO q4h
C. 40 mg PO QID
D. 50 mg PO q6h
B. Conversion of IV:PO morphine is 1:3. 40 mcg/kg/h x 40 kg x 24 h = 38,400 mcg/day = 38.4 mg IV/day x 3 = 115 mg PO/day / 24h = 4.8 mg PO/h = 20mg PO q4h (Barash Table 56-7)
All volatiles depress ventilatory response to hypoxemia. Which one preserves this response the most at 0.1 MAC? (2012/Q90)
A. Desflurane
B. Halothane
C. Isoflurane
D. Sevoflurane
A. Inhaled anesthetics, including N2O, also produce a dose-dependent attenuation of the ventilatory response to hypoxia. This action appears to depend on the peripheral chemoreceptors. In fact, even subanesthetic concentrations of volatile anesthetics elicit anywhere from a 25-75% depression of the ventilatory drive to hypoxia. (Barash p468)
With concerning thyroid storm: (2012/Q98)
A. Potassium iodide is given to reduce TSH
B. PTU is given IV for acute episodes
C. Mortality is 20%
D. Can occur 48h post-op
C. Antithyroid drugs (PTU 200-400 mg q8h) may be administered through an NG tube, orally or rectally. Serum thyroid hormone levels generally return to normal within 24-48h and recovery occurs within 1 week. The mortality rate for thyroid storm remains suprisingly high at approximately 20%. (Co-existing p389)
