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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Metoprolol Pharmacology

Metoprolol is a beta-blocker commonly used in the management of hypertension, heart failure, and atrial fibrillation.

There is an extended release dosage form and immediate release dosage form with metoprolol. The advantage of the extended release product is that it doesn’t require as frequent dosing.

Metoprolol is selective for beta-1 receptors. It is less likely to interact with asthma medications.

CYP2D6 plays an important role in breaking down metoprolol. Alterations in this enzyme’s activity can alter concentrations of the drug.

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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.

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Prasugrel Pharmacology

Prasugrel is a P2Y12 inhibitor that is used in the setting of ACS.

Be aware of patients who may be taking over the counter medications that can increase their bleed risk while taking prasugrel.

Prasugrel is on the Beers list and in general, should be avoided in most situations for patients who are 75 years of age or older.

Morphine has the potential to impact antiplatelet agents like prasugrel and make them less effective. Be sure this is clinically considered prior to using morphine with prasugrel.

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Clopidogrel Pharmacology

Clopidogrel is an antiplatelet agent that is often used in combination with aspirin to help reduce the risk of an MI.

The risk of bleed is a high priority with the use of clopidogrel. Patients must be monitored for signs and symptoms of bleeding and bruising.

Clopidogrel is a prodrug that is converted to its active metabolite by CYP2C19.

Fluconazole can inhibit CYP2C19 which may reduce the effectiveness of clopidogrel.

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Cholestyramine Pharmacology

On this episode, I discuss the pharmacology of cholestyramine.

Cholestyramine was originally developed as an agent to manage cholesterol, but has fallen out of favor for some of the more effective agents like statins.

Cholestyramine is notorious for binding drug interactions. It can reduce concentrations of drugs like amiodarone, digoxin, oral contraceptives, immunosuppressive and many more!

In patients with chronic diarrhea, cholestyramine is occasionally used off label to help manage symptoms because it tends to have constipating effects.

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Heparin Pharmacology

Heparin Pharmacology

Heparin is an interesting drug with a lot of unique clinical quirks. This drug ultimately inhibits the formation of fibrin. Fibrin is an essential component of a blood clot.

Because heparin has blood thinning effects, it is critical to assess a patient’s bleed risk. Look out for other agents that may increase the risk of bleeding. Examples include; NSAIDs, antiplatelet agents, and other anticoagulants.

One classic test question about heparin that often comes up is the reversal agent. Protamine can be used to help reverse the effects of heparin.

Heparin-induced thrombocytopenia is a critical adverse effect to understand. I discuss both subtypes on the podcast and let you know what to look out for.

Rarer side effects of heparin include hyperkalemia and osteoporosis (only with long term use).

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Ezetimibe Pharmacology

Ezetimibe Pharmacology

On this episode, I discuss ezetimibe pharmacology. Ezetimibe works by inhibiting Niemann-Pick C1-Like1 (NPC1L1) transporter. This transporter aids in cholesterol absorption so by blocking it, we can reduce cholesterol levels (and LDL) in the bloodstream.

Ezetimibe is usually very well tolerated. Diarrhea, myopathy, and elevations in LFT’s are adverse effects that have been reported but do not occur at high rates.

Ezetimibe is dosed at 10 mg once daily. This is a nice advantage because this is a starting dose and the usual treatment dose.

With the most recent cholesterol guideline updates, I do expect ezetimibe to be utilized a little more than it used to be. They place more emphasis on a target LDL and getting patients to goal.

Statins are going to be used first line for cholesterol and ezetimibe will be an add on therapy to consider. They don’t, unfortunately, lower cholesterol as much as high-intensity statins do.

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Rivaroxaban Pharmacology

Rivaroxaban is a factor 10a inhibitor that inhibits clot formation and thins the blood.

Rivaroxaban needs to be monitored for bleed risk. Checking periodic CBC can help us assess if hemoglobin and hematocrit are remaining stable.

Enzyme inducers like rifampin, St. John’s Wort, and carbamazepine can reduce concentrations and increase the risk of treatment failure.

NSAIDs and antiplatelet medications can significantly increase the risk of bleed with rivaroxaban.

Rivaroxaban should not be used with dual P-glycoprotein and CYP3A4 inhibitors. Examples include ketoconazole, itraconazole, and ritonavir.

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Hydralazine Pharmacology

Hydralazine Pharmacology

Hydralazine Pharmacology

Hydralazine works as a direct vasodilator. It primarily works on the arterioles versus the venous system.

Hydralazine can cause a unique adverse reaction. It can cause a Lupus type syndrome that can result in fever, myopathy and symptoms that mimic arthritis.

I discuss drug interactions with hydralazine and how you need to be aware of certain medications that can have additive effects and also those that can oppose the effects of the drug.

One of the downsides to using hydralazine is that patients don’t like to take it as often as it requires. It is typically dosed three to four times per day.

Orthostasis is a risk with any drug that reduces blood pressure and hydralazine is no different.

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