Diuretics 1
A diuretic that works BEFORE the collecting duct will _____ K+ excretion in the urine.
A diuretic that works IN the collecting duct will _____ K+ excretion in the urine.
Increase, decrease.
Drugs that conserve K+ are referred to as K+ sparing diuretics.
When should osmotic diuretics be used?
They should not be used to treat hypertension due to volume depletion/hypovolemia risk. They should be used to reduce intraocular pressure in acute glaucoma or to lower intracranial pressure.
During what phase of a ventricular action potential do Na+ channel blockers act?
Phase 0.
Individuals allergic to iodine should avoid this drug.
Amiodarone
For atrial arrythmias.
You're the medical provider for a expedition to climb Mt Everest. Among other things, what should be in your drug kit?
Acetazolamide to help prevent acute mountain sickness.
As you go up higher in altitude, O2 decreses. If you have less O2, you are exhaling less CO2, so you have a build up of CO2 in the body. That can bind to HCO3- in the kidney. Now carbonic anhydrase will make more H2CO3, this can go back into the cell and reabsorb more more HCO3-. This results in the blood pH becoming alkalotic.
Acetazolamide can help to prevent this.
On what receptor does spironolactone have a direct effect?
Acts on the mineralocorticoid receptor. It does not block aldosterone, it blocks aldosterone's ability to bind to the receptor.
A class 2B Na+ channel blocker has what effect on action potential, effective refractory period, and QT interval?
Decreases action potential, decreases effective refractory period, and shortens QT interval. Essentially shortens the repolarization. You're trying to slow down an abnormal heart beat. It will only be useful for a ventricular arrhythmia, it will have no effect on healthy individuals.
What is the mechanism of action of amiodarone?
(Will also blcok Na+ channels, B1 channels, K+ channels, Ca2+ Channels).
A patient who has peripheral edema as a result of their CHF needs to be placed on a loop diuretic. As part of your work up, you inquire about past medical history including allergies. They tell you they are allergic to sulfa drugs. What should you prescribe them?
Furosemide is considered a "High-ceiling" diuretic wherein most of the Na+ will be lost in the urine.
Mannitol is not reabsorbed or secreted, it is filtered. Too much mannitol in the tubular urine leads to an osmotic shift of water from the blood and into the lumen. It will "wash away all of the electrolytes due to the volume of water" very quickly. (Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, (PO4)3-).
What arrhythmias would you treat with Class 1A Na+ channel blockers?
A drug that can be used in atrial fibrillation, atrial flutter, supraventricular tachycardia, ventricular tachycardia, or ventricular fibrillation, will primarily acton on what phase of the ventricular action potential?
Phase 3. Will prolong ventricular repolarization.
A beta blocker will have what effect on the ECG tracing?
It will prolong the PR interval. (Slows the heart rate)
At which part of the nephron does hydrochlorothiazide work?
At the distal tubule. Acts at the Na/Cl- co-transporter. To compensate for the lower intracellular Na+, the Ca2+/Na+ exchanger works overtime, and more Ca2+ will be reabsorbed. You will excrete Na+ and water.
K+ is excreted b/c whatever Na+ isn't reabsorbed will make it to the collecting duct which will help with the reabsorption of more Na+. The more Na+ that is reabsorbed, the more K+ is excreted.
Under normal physiological conditions, how does arginine vasopressin/Anti-diruetic hormone work?
Activates V2 receptors which increases cAMP. This results in aquaporin channels being inserted in the lumen of the collecting duct. This causes reabsorption of *water*. NOT Na+.
Increasing the QT can have what electro-physiological outcome?
Torsades des Pointes can develop when the QT interval is prolonged.
A patient with a ventricular arrhythmia who cannot tolerate amioderone should be treated with what?
Ibutilide and sotalol, works similary but is Class 3 and beta blocker.
An additional action potential that manifests before completing the present action potential is described as what kind of secondary depolarization?
What is the name of a drug that is used to treat hyponatremia but can cause hypernatremia? How does it work?
Tolvaptan. Blocks the binding of AVP/ADH which ill decrease cAMP, decrease PKA, and lead to AQP2 receptors in the collecting duct. There will be less water reabsorption as it will stay in the lumen and be excreted in the urine.
Lidocaine's effects will predominate in which chambers of the heart?
The ventricles
Why should cardiogenic shock and heart block patients avoid amiodarone?
Because their heart function is already impaired as it is. Amiodarone will have Class 2 and Class 4 action as well which will decrease conduction through the AV node and decrease the heart rate. You don't want to further decrease cardiac output in an individual who is already impaired.
How do the resting membrane potentials vary between ventricular myocytes and atrial pacemaker cells?
Ventricular -90mV. Atrial -70mV