Pharmacology 3 Flashcards
What is the mechanism of action of hydrochlorothiazide?
Hydrochlorothiazide is a diuretic used primarily for hypertension that works by blocking the Na-Cl co-transporters in the distal convoluted tubules of the kidney, thereby decreasing Na+ and Cl- reabsorption.
A 23-year-old 76 kg male is about to undergo surgery for an inguinal hernia. Standard ASA monitors are placed and the patient is preoxygenated for 3 minutes prior to induction. He receives 200 mg of propofol mixed with 40 mg of lidocaine, 100 mcg of fentanyl, and 8 mg of vecuronium for induction. Which of the following is TRUE regarding pain on injection with propofol?
Mixing propofol with lidocaine has been shown to decrease the stability of the propofol emulsion and may cause pulmonary embolism. The FDA recommends against mixing propofol with any other therapeutic medications prior to administration. The most effective methods to reduce pain are propofol injections using an antecubital vein and a modified Bier block prior to injection.
Amiloride is MOST commonly associated with which of the following electrolyte imbalances?
Potassium-sparing diuretics can cause hyperkalemia by blocking potassium secretion in the distal collecting ducts. Thiazide diuretics can cause hypercalcemia due to their effects on the sodium-calcium exchanger in the distal convoluted tubule. Loop diuretics can cause hypokalemia and hyponatremia by affecting the TAL. Carbonic anhydrase inhibitors can cause metabolic acidosis, which may lead to hyperkalemia if untreated.
TrueLearn Insight : Acetazolamide is the treatment of choice for high-altitude/mountain sickness due to its ability to eliminate CSF alkalosis. A mnemonic for the potassium-sparing diuretics is: “The K+ STAys,” for Spironolactone, Triamterene, and Amiloride.
Which of the following is MOST suggestive of a diagnosis of sodium nitroprusside toxicity?
Sodium nitroprusside administration has the potential for causing toxicity due to the accumulation of its metabolic byproducts: cyanide and thiocyanate. Common presenting signs of cyanide toxicity include elevated PVO2, tachyphylaxis to SNP, metabolic acidosis, and flushing. Symptoms of thiocyanate toxicity include hypoxia, nausea, tinnitus, muscle spasm, disorientation, and psychosis.
TrueLearn Insight : Amyl nitrate works as an antidote for cyanide poisoning by converting Hb to MetHb which avidly binds cyanide, converting it to the nontoxic cyanomethemoglobin.
Which of the following opioid drugs is the MOST nonionized at physiologic pH?
A unique characteristic of alfentanil relative to other opioids is its significantly lower pKa resulting in a very high fraction of the drug existing in the nonionized form. Coupled with its moderate lipid solubility, this allows alfentanil to very rapidly cross the blood-brain barrier and have an ultra-short onset of action. The plasma-brain equilibration half-time of alfentanil is 0.9-1.1 minutes compared to 6.2 minutes for sufentanil, 4.7-6.4 minutes for fentanyl, and 139 minutes for morphine.
Which of the following is TRUE regarding the effects of diuretics on electrolytes?
: Diuretics result in the excretion of sodium from the body. Calcium is excreted by loop diuretics and reabsorbed by thiazide diuretics.
You have just extubated a patient where antagonism of the nondepolarizing muscle blockade with neostigmine occurred. You need to urgently reintubate the patient and succinylcholine 1 mg/kg is administered. Which of the following do you expect for the duration of action of succinylcholine?
Following neostigmine administration, a dose of succinylcholine will result in an increased duration of phase I blockade when compared to the duration of action of succinylcholine administered alone. Phase I augmentation lasts about 30 minutes on average.
Which of the following statements is the LEAST descriptive of zero order kinetics?
First order kinetics describes a situation where a constant proportion (percentage) of a medication is removed per unit time, whereas zero order kinetics describes a situation where a constant amount of medication is removed per unit time.
Liver blood flow dependent elimination is characteristic of first-order kinetics, not zero-order kinetics.
It is important to remember that drug metabolism via first or second order kinetics is not an inherent property of a medication, but rather a way to describe mathematically how these drugs behave in vivo.
TrueLearn Insight : Drugs that typically follow zero-order kinetics are THE PAW: theophylline, heparin, ethanol, phenytoin, aspirin, warfarin.
A 29-year-old, 62 kg female undergoes an open reduction and external fixation of a distal radius fracture after a snowboarding accident. She takes loratadine for seasonal allergies, fluoxetine for depression, and oral contraceptive pills. During the procedure, she receives 70 mg of rocuronium and is reversed with sugammadex. Which of the following is MOST likely to be a side effect of sugammadex?
The two most important adverse effects of sugammadex include anaphylaxis/hypersensitivity reactions and potentially severe bradycardia. Other important adverse effects include, but are not limited to arrhythmias, tachycardia, hypotension, prolongation of PT/INR and aPTT, and increased risk of unintentional pregnancy due to inactivation of hormonal contraceptives.
TrueLearn Insight : Sugammadex has no affinity for succinylcholine or benzylisoquinolinium neuromuscular blocking drugs (e.g. cisatracurium) and will not reverse their effects.
A patient undergoing laparoscopic appendectomy has received rocuronium for muscle relaxation at intubation. What is the mechanism of action for this medication?
All non-depolarizing neuromuscular blockers act as competitive antagonists at the postsynaptic nicotinic acetylcholine receptor.
Which of the following hemodynamic effects is MOST LIKELY to be seen immediately following 0.5 g/kg administration of mannitol given intravenously over twenty minutes?
After administration of mannitol, an increase in plasma volume will occur which will result in an increase in blood pressure and cardiac output. This may lead to an increase in pulmonary capillary wedge pressure, especially in patients with heart failure.
Which of the following is the FIRST expected sign or symptom of central nervous system toxicity from intravenous lidocaine administration?
Lidocaine toxicity is dependent on dose and site of injection. The most common cause is dosing error. The maximum dose (commonly cited) of lidocaine with and without epinephrine is 7 mg/kg and 5mg/kg, respectively. Central nervous system toxicity is first noted by circumoral and tongue numbness. Areas of regional anesthesia from highest to lowest vascularity include: intravenous > tracheal > intercostal > caudal/paracervical > epidural > brachial plexus > sciatic/femoral > spinal > subcutaneous.
Which of the following describes the mechanism by which the duration of action of rocuronium is prolonged when desflurane is used?
Volatile anesthetics potentiate neuromuscular blockade by DECREASING sensitivity of the postjunctional membrane to depolarization and INCREASING skeletal muscle blood flow which both augment neuromuscular blockade. In addition, potentiation of neuromuscular blockade occurs by depression of upper motor neurons.
Which of the following statements regarding milrinone is TRUE?
Milrinone is a second generation phosphodiesterase III (PDE III) inhibitor. Both PDE I and PDE II hydrolyze all cyclic nucleotides, but PDE III acts on cAMP specifically. Milrinone is excreted via the kidneys in its unconjugated form and therefore dosage should be adjusted in the setting of renal failure. Milrinone is unique in its ability to increase cardiac index without increasing myocardial oxygen demand. It also improves myocardial relaxation (lusitropy) and augments coronary circulation.
Milrinone increases cardiac index while reducing systemic and pulmonary vascular resistance.
A 68-year-old male is undergoing a hemicolectomy for colon cancer. He is maintained on 1% isoflurane and fentanyl boluses. Rocuronium is used for paralysis and is titrated to a single twitch on the peripheral nerve stimulator. Intraoperatively the surgeon complains of inadequate paralysis and requests further relaxation. Assessment of which of the following muscles is the MOST representative of abdominal muscle paralysis?
After laryngeal muscles and diaphragm, the corrugator supercilii (eyebrow movement) is the most resistant to neuromuscular blockade and most closely resembles the abdominal and laryngeal muscles. The adductor pollicis is more sensitive to neuromuscular blockade and is the best choice to monitor for extubating conditions. The flexor hallucis (big toe flexion) and orbicularis oculi (eyelid movement) correlate more closely with the adductor pollicis.
