Real Life Pharmacology - Pharmacology Education for Health Care Professionals

On this episode, I discuss the pharmacology surrounding QTc prolongation and drug interactions. I discuss which medications are more likely to cause QTc prolongation and which patient populations we should be more concerned about. Antiarrhythmics are a common class of medication that can exacerbate QTc prolongation when used with other interacting medications. 500 ms is a common value utilized to help identify patients at risk for QTc prolongation and ultimately torsades de pointes.

On this podcast episode, I cover risedronate pharmacology, adverse effects, drug interactions, and much more. There is a strict administration procedure with risedronate which is designed to reduce adverse effects and enhance absorption. I discuss this in the podcast. Many medications may cause osteoporosis and may precipitate treatment with risedronate. Corticosteroids and excessive thyroid hormone replacement are two examples. Patients should remain upright (sitting or standing) for at least 30 minutes following administration to reduce the risk of esophagitis and ulceration.

On this podcast episode, I discuss some of the most common antihypertensive drug interactions you need to know. One major interaction I discuss is the trifecta of a diuretic, an ACE or ARB, and an NSAID. This combination significantly increases the risk for acute renal failure. Nitrates aren't classically referred to as an antihypertensive but they can definitely cause some problems when combined with PDE5 Inhibitors. Lithium can interact with 3 blood pressure medication classes. ACEIs, ARBs, and diuretics can all increase the risk for lithium toxicity.

Teplizumab is a relatively new agent that helps delay the progression of type 1 diabetes. It slows the rate of beta-cell destruction in the pancreas. Teplizumab is associated with cytokine release syndrome which can result in flu-like symptoms of fever, aches, and headache. Cytokine release syndrome due to teplizumab can be reduced by using appropriate pretreatment medications. Those medications can include analgesics, antihistamines, and/or antiemetics. Teplizumab is associated with suppressing the immune system so it is ideal to get vaccinations completed before using this medication. I go over the specific recommendations in the podcast episode.

On this podcast episode, I discuss captopril pharmacology, kinetics, interactions, and much more! Captopril is an ACE Inhibitor. It can cause hyperkalemia, cough, and renal impairment. One of the notable issues with captopril is its relatively short half-life which requires it to be dose frequently throughout the day. Lithium is an important drug interaction and the use of captopril with this medication may increase concentrations and the chance for toxicity.

On this episode of the Real Life Pharmacology podcast, I take a dive into the most common mechanisms of drug interactions. Below I list some of the common drug interactions seen in practice and how they work! Opposing Effects Many drugs will work on various receptors throughout the body. To use as an educational point, there is no better example to point to than the beta receptor. Beta-blockers are frequently used in clinical practice for their ability to lower blood pressure and slow the heart rate. Both of these beneficial actions are primarily achieved by blocking the effects of beta-1 receptors. Some beta-blockers have action on alternative beta receptors. Propranolol is one such beta-blocker that is classified as a non-selective beta-blockers. This means that in addition to the positive effects on beta-1 receptors, it can also have blocking effects on beta-2 receptors. The blockade of the beta-2 receptor by propranolol can also be life-changing. It can directly oppose beta-2 agonists like albuterol from having their beneficial effects of opening up the airway. Enzyme Inhibition Medication metabolism is arguably the largest and most clinically significant source for drug interactions. Medications that are primarily metabolized by enzymes in the liver can be greatly affected if we affect how those enzymes work. CYP3A4 is one of the most well studied and well-known enzymes that can impact hundreds to maybe even thousands of drugs. Apixaban is an oral anticoagulant that is broken down at least in part by CYP3A4. By using a CYP3A4 inhibitor like erythromycin, there is the potential to raise concentrations of apixaban. This could lead to a higher risk of bleeding. Enzyme Induction Carbamazepine is a drug that you must know. This drug is a potent enzyme inducer. This differs significantly from an enzyme inhibitor and will have the exact opposite clinical effect. Drugs that are inactivated by liver enzymes will be inactivated more quickly in a patient taking an enzyme inducer. Going back to our prior apixaban example above, carbamazepine can induce CYP3A4 and facilitate a more efficient and swifter breakdown of the drug. Bleeding will be less likely. The risk for treatment failure, usually in the form of a blot clot, will be more likely.  Here’s more information from the past on carbamazepine. Alteration in Absorption Binding interactions can be consequential and are one of the most common types of drug interactions. Many medications have the potential to bind one another in the gut. This can lead to lower concentrations of a specific medication. Calcium and iron are two of the most common examples of medications that can bind other drugs. Alteration in Protein Binding By remembering that unbound drug is an active drug, you should appreciate the risk for protein binding alterations. A significant number of medications can bind proteins in the bloodstream. As this occurs, that drug is not freely available to create physiologic effects. When another medication is added that can also bind these proteins, this can displace other medications and increase the quantity of free drug in the bloodstream. This essentially allows for enhanced physiologic effects. Warfarin is a medication that is highly protein-bound. When another drug is added that can kick warfarin off of those protein binding sites, it can free up warfarin which will increase the likelihood of elevating the patient’s INR and increase their bleed risk. Alteration in Renal Elimination Some drugs can alter the way other medications are eliminated through the kidney.

On this podcast episode, I discuss insulin aspart pharmacology, adverse effects, drug interactions, and much more. Insulin apart is a rapid acting insulin product meant to bring down blood sugars quickly (most often after meals). It is important to remember a couple of medications that may counteract the effects of insulin and apart and raise blood sugar. I talk about corticosteroids and thiazide diuretics in the drug interaction section. Fiasp is a slightly modified insulin aspart molecule that allows for quicker absorption. This quicker absorption will allow for blood sugars to come down sooner than the Novolog formulation.

On this podcast episode, I discuss gentamicin pharmacology, adverse effects, monitoring, drug interactions and much more! Drug monitoring is critical with gentamicin. Trough and peak concentrations can guide therapy and identify someone at risk of toxicity. Nephrotoxicity is a major concern with gentamicin. There are numerous nephrotoxic agents that can increase this risk. I discuss them on the podcast. Ototoxicity is another risk associated with gentamicin. Loop diuretics like furosemide can increase this risk. Learn more on this podcast episode.

On this podcast episode, I discuss fenofibrate pharmacology, adverse effects, kinetics, drug interactions, and much more! Fenofibrate is typically only used for hypertriglyceridemia. The primary risk of hypertriglyceridemia is pancreatitis so we treat these levels because of this risk. LFTs elevation has been associated with fenofibrate use as well as myopathy. In the presence of myopathy, checking CPK may be considered. Fenofibrate is a weak CYP2C9 inhibitor. Warfarin and phenytoin are two important medications that may be affected by the use of fenofibrate.

On this podcast episode, I discuss levofloxacin pharmacology, adverse effects, boxed warnings, interactions, and much more. Levofloxacin is well known to cause QTc prolongation and many drugs can increase this risk such as antiarrhythmics, citalopram, antipsychotics, and many more. Binding interactions are important when discussing levofloxacin pharmacology. Calcium, iron, magnesium, and many other cations can block the absorption of this medication. I discuss tendon rupture in relation to levofloxacin use and what factors may increase the risk of this rare adverse effect.

On this podcast episode, I discuss darifenacin pharmacology, adverse effects, drug interactions and much more. CYP3A4 and CYP2D6 are important enzymes in relation to darifenacin. I breakdown the importance of these enzymes and how they can impact drug therapy. Darifenacin has anticholinergic activity but affects the central nervous system less than other agents in its class such as oxybutynin and tolterodine. Darifenacin's pharmacology is selective for the Muscarinic-3 (M3) receptor in bladder tissue which helps reduce the risk for CNS adverse effects.

In this podcast episode, I discuss naltrexone pharmacology, adverse effects, drug interactions, and much more. Naltrexone is an opioid antagonist and can blunt the effects of opioid agonists. Because of this, the medication can be used to manage opioid use disorder. Hepatotoxicity is a concern of naltrexone and because of this, it is recommended to monitor LFTs. There is an injectable, long-acting formulation of naltrexone that can be used for opioid and alcohol use disorder treatment.

On this podcast episode, I discuss acamprosate pharmacology, adverse effects, drug interactions, and much more! Acamprosate's most common adverse effect is diarrhea. It is a primary reason why patients will ask to stop taking this medication. It is critical to assess renal function prior to using acamprosate. Dose adjustments are recommended when patients have a CrCl of less than 50 ml/min. Unlike naltrexone, acamprosate avoids liver metabolism making it an alternative option in alcohol use disorder for patients who have liver impairment.

On this podcast episode, I discuss alfuzosin pharmacology, adverse effects, drug interactions, and much more! Alfuzosin is an alpha blocker used to help relieve the symptoms of BPH. Low blood pressure is a possible adverse effect of alfuzosin and is more likely when combined with PDE-5 inhibitors like sildenafil. CYP3A4 is an important enzyme in the metabolism of alfuzosin. Inhibitors of CYP3A4 can raise concentrations and increase the chance of alfuzosin toxicity.

In this podcast episode, I discuss methadone pharmacology, adverse effects, drug interactions, and pharmacokinetics. Methadone is a full opioid agonist that may be used for pain management and opioid use disorder. Transitioning from methadone to another opioid is complicated. I discuss conversion in this podcast episode. Methadone can increase the risk of QTc prolongation and also has a lot of drug interactions. I discuss them in detail in this podcast episode.