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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Sulfasalazine Pharmacology

Sulfasalazine is a medication that can be used for diseases like rheumatoid arthritis, Crohn’s disease, and Ulcerative Colitis.

Because sulfasalazine can cause GI upset, this is a major reason why we try to break up the dose and give it multiple (at least two) times per day.

LFT and CBC monitoring are recommended with sulfasalazine due to its low potential to cause liver dysfunction, aplastic anemia, and agranulocytosis.

Sulfasalazine can impair folic acid absorption and lead to potential deficiency. A patient deficient in folic acid is at higher risk for developing anemia.

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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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Rifampin Pharmacology

Rifampin is classified as an antibiotic and an antituberculosis agent. It primarily works by inhibiting bacterial RNA polymerase.

While not extremely common, rifampin is well known to cause hepatic dysfunction.

You should remind patients who are taking rifampin that it can alter the color of tears, sweat, saliva and urine. It can change these fluids to a reddish/brown color.

Rifampin is very well known for causing drug interactions. It is an enzyme inducer that can reduce the concentrations of numerous medications such as warfarin, apixaban, cyclosporin, levothyroxine, and oral contraceptives to name a few.

Rifampin can be used to help prevent meningococcal infection. Learn more on rifampin by listening to this podcast!

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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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Montelukast Pharmacology

Montelukast Pharmacology

On this episode, I discuss montelukast pharmacology

Montelukast is a leukotriene receptor antagonist. Leukotrienes play an important role in causing inflammation and smooth muscle contraction in asthma and allergic rhinitis.

Because montelukast blocks the effects of leukotrienes, it can be advantageous to use this medication for allergies and asthma.

It is important to remind patients that montelukast is NOT a substitute for an acute relief medication like albuterol in the management of asthma symptoms.

Montelukast has been reported to cause mood and behavioral changes and it is important to monitor our patients for these rare concerns.

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Clozapine Pharmacology

Clozapine Pharmacology

On this episode, I discuss clozapine pharmacology. This drug has multiple mechanisms of action: Dopamine blockade, anticholinergic activity, and alpha blocking activity all contribute to the complexity of this drug.

Smoking cessation can significantly increase the concentrations of clozapine. This is because smoking can induce CYP1A2. Listen to the podcast for more details on how this can impact our patients clinically.

Clozapine has 5 boxed warnings. I discuss them all in this podcast. The most well-known boxed warning is for agranulocytosis.

Because clozapine has alpha blocking activity, it can cause orthostasis. We need to monitor for this.

Clozapine can cause QTc prolongation. Keep an eye out for other medications that the patient may be taking that can also cause this. Examples include: amiodarone, ondansetron, quinolones, and macrolides

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Carbamazepine Pharmacology

Carbamazapine Pharmacology

On this episode, I discuss carbamazepine pharmacology. This drug is most commonly used for seizures, bipolar disorder, or trigeminal neuralgia.

Carbamazepine is an autoinducer and can reduce the concentrations of numerous drugs. Some examples include apixaban, warfarin, rivaroxaban, diltiazem, verapamil, and many more!

Carbamazepine has the potential to cause Steven Johnson’s Syndrome. This has a much greater chance of happening in patients with certain genetics.

Carbamazepine can contribute to SIADH and cause significant hyponatremia.

Carbamazepine has boxed warning for numerous potential events like aplastic anemia, agranulocytosis, and the above-mentioned SJS.

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Stimulant Laxatives Pharmacology

Stimulant Laxative

On this episode, I discuss the pharmacology of commonly used stimulant laxatives like sennosides and bisacodyl.

Stimulant laxatives “stimulate” the GI tract smooth muscle which helps propel fecal material out of the body and thus helping to relieve constipation.

Patients who are having diarrhea and are unsure of what medications they are taking should have their regimen assessed for these medications.

Chronic opioid therapy is a situation where chronic stimulant laxative therapy may be used.

Stimulant laxatives have very few drug interactions. However, bisacodyl effectiveness can be reduced by the use of antacids like calcium carbonate.

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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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