Torsemide Pharmacology

On this episode, I discuss torsemide pharmacology, adverse effects, drug interactions and pharmacokinetics.

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Sacubitril Valsartan Pharmacology

On this episode, I breakdown the sacubitril valsartan pharmacology.

The drug for this week is the combination drug sacubitril/valsartan, also known as Entresto. Entresto has a novel dual mechanism of action to treat HFrEF. Sacubitril, currently, is the only FDA-approved medication that is a neprilysin inhibitor. For background, neprilysin is an enzyme that breaks down natriuretic peptides. The inhibition of neprilysin results in an increase in natriuretic peptides, which causes vasodilation, fluid loss, and a decrease in blood pressure. Valsartan is an angiotensin II receptor blocker; it prevents angiotensin II from binding to AT1 to reduce blood pressure by reducing vasoconstriction, synthesis, and release of aldosterone and ADH, cardiac remodeling, and renal reabsorption of sodium. The unique pharmacology of Entresto makes it advantageous to use in HFrEF and is even now one of the preferred agents.

Common adverse reactions that occur when taking Entresto are related to its dual mechanism pharmacology. The most common adverse reactions of Entresto are hyperkalemia, angioedema, hypotension, and renal impairment. Entresto is contraindicated in pregnancy due to fetotoxicity; it requires a 36 hour washout period when transitioning from an ACE inhibitor due to the increased risk of angioedema. 

Entresto is initially dosed at 24/26 mg twice a day if the patient is on a low dose ACE inhibitor/ARB, or if the patient has not taken anything. If a patient is taking over 10 mg of enalapril equivalents a day or 160 mg of valsartan equivalents a day, then the preferred initial dose is 49/51 mg twice a day. Regardless of initial dosing, the target dose is 97/103 mg twice a day. In cases of severe renal impairment, or moderate hepatic impairment, the initial dosing should start at 24/26 twice a day; titration remains the same. 

The pharmacology of Entresto leaves room for many potential drug-drug interactions. There’s a risk of duplicate therapy with other ACE inhibitors or ARBs. An exacerbation of adverse drug reactions can also occur when taking medications that can lower blood pressure, like Sinemet, or medications that can increase the risk for hyperkalemia, like trimethoprim, and spironolactone, or medications that can increase the risk of renal impairment, like NSAIDs. Entresto has also been shown to increase the risk of lithium toxicity.

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Show notes provided by Chong Yol G Kim, PharmD Student.

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Furosemide Pharmacology

Furosemide is a loop diuretic most commonly recognized by its brand name, Lasix. Pharmacologically, it acts by inhibiting the reabsorption of Na/Cl in the thick ascending limb of the loop of Henle. The inhibition of electrolyte reabsorption results in a loss of fluids causing diuresis. Since it has a diuretic effect, it is commonly used to treat congestive heart failure, general edema, ascites due to cirrhosis, and to aid in fluid elimination. 

If a patient has a new prescription of furosemide, it’s important to look for drug-induced causes of edema. Common causes of drug-induced edema are the calcium-channel blockers (amlodipine, nifedipine, diltiazem, verapamil), some anticonvulsants (pregabalin, gabapentin), pioglitazone, and NSAIDs. In times when oral furosemide is not readily available, 40 mg of furosemide is equivalent to roughly 20 mg torsemide, or 1 mg bumetanide. If IV furosemide is desired and the patient is already on an oral formulation, generally, the approximate equivalent IV dose is 50% of the oral dose. Dosing is approximate and based on urine output. Serum creatinine, electrolytes, weight, blood pressure, should generally be monitored due to the pharmacology of furosemide.

Common adverse drug reactions of furosemide associated with its pharmacology are hypokalemia, and its symptoms such as cramping and uncommonly cardiac problems, hypotension, hyponatremia, dehydration, decrease in renal perfusion, uric acid elevation, transient increases in glucose, angioedema and hypersensitivity reactions, ototoxicity, and nephrotoxicity. Drugs that can exacerbate furosemide’s adverse drug reaction profile are ARBs, ACEis, NSAIDs, aminoglycoside, SGLT2 inhibitors, PDE5 inhibitors, a1a blockers. Electrolyte supplementation may be provided to patients on furosemide to counteract any imbalances that may precipitate. 

In cases of overdose, the common symptoms are exacerbations of the adverse drug reactions and mechanism, dehydration, electrolyte imbalances, hypochloremic alkalosis, reduction in blood volume, and hypotension. Supportive treatment of symptoms is necessary to treat furosemide overdoses, fluid and electrolyte replacement is a rational method of treatment. Serum electrolytes, CO2 level, and blood pressure should be monitored in overdose situations. Hemodialysis does not accelerate furosemide elimination.

Show notes provided by Chong Yol G Kim, PharmD Student

Be sure to check out our free Top 200 study guide – a 31 page PDF that is yours for FREE!

Study Materials For Pharmacists and Students

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Resources

  1. Information taken directly from the podcast episode
  2. Dosing goals diuresis end of paragraph 2: 2013 ACCF/AHA guideline for the management of HF https://doi.org/10.1161/CIR.0b013e31829e8776
  3. Last paragraph on overdose, furosemide FDA label

Metolazone Pharmacology

Metolazone (Zaroxolyn) is a thiazide-like diuretic. It promotes the loss of water and sodium through the kidney.

The most common indication I see metolazone used for is for additional fluid loss in heart failure.

Potassium must be monitored as it can cause significant hypokalemia which is exacerbated when metolazone is used in combination with loop diuretics.

Hyperuricemia is a potential adverse effect with metolazone; this is critical to monitor for in patients at risk for gout attacks.

I discuss important drug interactions on the podcast, be sure to check out my latest project which is a 200+ page book on managing drug interactions in primary care.

Be sure to check out our free Top 200 study guide – a 31 page PDF that is yours for FREE!

Diltiazem Pharmacology

Diltiazem is a non-dihydropyridine calcium channel blocker that can be used in atrial fibrillation as well as hypertension.

One big downside to diltiazem is that it does have a few drug interactions via CYP3A4.

Aripiprazole, apixaban, and certain statins are all examples of medication that can have concentrations increased by adding diltiazem to a patient’s regimen.

Diltiazem works a little differently from dihydropyridine calcium channel blockers (like amlodipine) as it works on the heart AND the vessels.

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Cilostazol Pharmacology

Cilostazol has antiplatelet and vasodilatory effects. Because of this, it can manage symptoms of intermittent claudication.

GI upset, headache, and edema are common adverse effects associated with the use of cilostazol.

Cilostazol is recommended to be given on an empty stomach.

In patients with heart failure, cilostazol use is contraindicated.

CYP3A4 interactions are prevalent with cilostazol. Inhibitors of CYP3A4 can increase the concentrations of cilostazol.

Be sure to check out our free Top 200 study guide – a 31 page PDF that is yours for FREE!

Amiodarone RLP Episode 014

On today’s episode I discuss all the unique clinical pearls associated with amiodarone (Cordarone).  Hope you enjoy the episode!

All subscribers to the website/podcast will get access to a FREE Top 200 Drug Study Guide where I highlight the 3 most highly testable pearls from each medication (this is a 31 page PDF!)  In addition, you’ll get a free 100 question pharmacology test.  Both resources are free, simply for following the podcast!  What are you waiting for? Click Here to Subscribe

Digoxin Pharmacology – RLP Episode 011

On this episode I explain digoxin pharmacology and also run through some scenarios where I’ve seen digoxin toxicity actually happen.

I also discuss the relationship of low potassium and how digoxin can have an exacerbated effect in this setting.  Hope you enjoy the episode and please feel free to reach out and give me some feedback!

All subscribers to the website/podcast will get access to a FREE Top 200 Drug Study Guide where I highlight the 3 most highly testable pearls from each medication (this is a 31 page PDF!)  In addition, you’ll get a free 100 question pharmacology test.  Both resources are free, simply for following the podcast!  What are you waiting for? Click Here to Subscribe

Eric Christianson, PharmD, BCGP, BCPS