Real Life Pharmacology - Pharmacology Education For Health Care Professionals

Conjugated estrogens (Premarin) are most often used in the management of menopausal symptoms. Estrogen therapy can increase the risk for breast cancer and the risk should be assessed before beginning therapy. Blood clots are a potential consequence from the use of Premarin. Premarin can oppose the benefit of anticoagulation. Conjugated estrogens are broken down by CYP3A4. Inhibitors may increase concentrations while inducers may reduce concentrations.

Paroxetine (Paxil) is an SSRI that can be used in the management of depression. I discuss more on paroxetine pharmacology in this episode. Because paroxetine has some modest anticholinergic effects, it does show up on the Beers list as a potentially inappropriate medication. By inhibiting CYP2D6, paroxetine can have numerous drug interactions. Drugs like atomoxetine, aripiprazole, and metoclopramide can all have their concentrations increased. Tamoxifen is activated by CYP2D6 and paroxetine can ultimately reduce the effectiveness of the medication.

Olanzapine is a 2nd generation antipsychotic that blocks dopamine-2 receptors. Olanzapine Relprevv (long acting injectable) needs to be closely monitored after the injection is given due to risks of sedation and delirium. Sedation is a common occurance with the use of olanzapine. It is one of the more sedating second generation antipsychotics. Weight gain, hyperlipidemia, and hyperglycemia are all potential adverse effects with olanzapine.

Tizanidine is primarily broken down by CYP1A2. Ciprofloxacin can inhibit CYP1A2 and cause higher tizanidine concentrations. Tizanidine has a similar classification as clonidine. Pay attention to adverse effects like hypotension and bradycardia. When patients taking routine tizanidine stop taking it, there is potential for a discontinuation syndrome that may lead to rebound hypertension. Dry mouth and CNS depression are common adverse effects of tizanidine.

Valacyclovir can be used for various viral infections such as herpes virus and varicella. The primary clinical advantage of valacyclovir compared to acyclovir is that it is dosed less frequently. Valacyclovir may have some mild CYP1A2 inhibitory effect. I discuss the clinical relevance of this on this episode. GI upset can occur so I usually recommend to give it with food even though it may be given with or without food.

Abacavir is a nucleoside reverse transcriptase inhibitor used in the management of HIV. In patients who have the HLA-B*5701 allele, they are at much greater risk for hypersensitivity reactions. Lactic acidosis and hepatomegaly are potential complications with the use of abacavir. While abacavir is not known for a large number of drug interactions, I discuss a few that you have a chance to run into.

Sertraline is an SSRI. It has the highest potential to cause diarrhea of any SSRI. Sertraline is often called "Squirtraline" because of its potential to cause diarrhea. Sertraline has a much shorter half-life than fluoxetine. I discuss why that may be important in this podcast episode. I discuss the role of serotonin in platelet aggregation and how sertraline may affect this.

Fosfomycin is an antibacterial agents that can be utilized in the management of uncomplicated UTIs. Uniquely, fosfomycin comes as a packet that needs to be mixed with COOL water. I discuss this further on the podcast. Typhoid and Cholera vaccine effectiveness may be reduced when used with fosfomycin. When there is kidney or systemic infection involvement, it is recommended to avoid the use of fosfomycin.

Simvastatin use has declined over time due to more potent statins being available and due to numerous drug interactions. Grapefruit juice can inhibit CYP3A4 which will increase the concentrations of simvastatin. Genetic variations in SLCO1B1 can lead to patients being more susceptible to simvastatin toxicity. Simvastatin is a lipophilic statin. I discuss why this is important and how it might impact clinical decisions.

Citalopram is an SSRI used in the management of depression, anxiety, OCD, and PTSD. How do you manage the risk of citalopram causing QTc prolongation? I discuss it further in the podcast. Omeprazole can inhibit CYP2C19 which affects the metabolism of citalopram. I discuss the clinical impacts of this interaction in the podcast. Geriatric dosing with citalopram is recommended to be lower than traditional adult dosing. I discuss this further in the podcast.

Epoetin alfa is essential exogenous erythropoetin which can stimulate the production of red blood cells. It is critical to ensure adequate iron stores when using EPO. Risks for blood clots, strokes and heart attacks are critical to recognize with the use of epoetin. Dosage adjustments with epoetin are typically made with respect to the amount of change in hemoglobin. I discuss this further in the podcast.

Dexamethasone has numerous possible indications such as asthma, chemotherapy-induced nausea and vomiting, and pain associated with inflammation. Dexamethasone is more potent than prednisone. Approximately 0.75 mg of dexamethasone is equivalent to 5 mg of prednisone. When using dexamethasone, recall that it can raise blood sugars. Monitor this closely in patients with diabetes. A dexamethasone suppression test helps detect excessive endogenous production of cortisol.

On this episode, I discuss sildenafil pharmacology, adverse effects, and important drug interactions. Sildenafil's most common and concerning adverse effect is in relation to its ability to lower blood pressure. I discuss this further in the podcast. Sildenafil can cause rare visual changes that patients should be aware of and report immediately to their pharmacist or physician. The sildenafil nitrate interaction is essential to know. I discuss it in this podcast episode.

On this episode, I discuss codeine pharmacology and practical clinical practice pearls. Codeine is metabolized by CYP2D6 to the active metabolite morphine. I discuss how this can be affected by genetics as well as other medications. Constipation is a problem with codeine and all opioids in general. Education and making a plan with patients to combat this side effect is important. Codeine is less potent than other opioids such as fentanyl, hydromorphone, and hydrocodone.

Dexmedetomidine is a selective alpha-2-adrenergic agonist with sedative characteristics. Dexmedetomidine is commonly used in ICU and procedural sedation, as well as postoperative pain. A few of the more serious adverse effects of dexmedetomidine to keep an eye on including bradyarrhythmias/bradycardia and hypotension. Dexmedetomidine undergoes hepatic metabolism, meaning a dose reduction may be required in patients with impaired hepatic function. Major drug interactions to monitoring for with dexmedetomidine include co-administration with anesthetics, sedatives, hypnotics, and opioids, as it may lead to an enhancement of effects. It is also important to note that dexmedetomidine may produce withdrawal symptoms if used for longer than 24 hours.

On this episode, I discuss the pharmacology of calcitonin. Calcitonin has an indication for osteoporosis as well as hypercalcemia. When considering drug interactions with calcitonin, recall that it can lower calcium levels which could have a cumulative effect when combined with loop diuretics. Calcitonin nasal spray should be stored upright and primed prior to use.

Rivastigmine is an acetylcholinesterase inhibitor used in the management of certain dementias. I discuss rivastigmine pharmacology on this episode. Weight loss is a potential adverse effect of rivastigmine. It is important to monitor weights. Anticholinergic medications such as diphenhydramine can blunt the effects of rivastigmine. Rarely, acetylcholinesterase inhibitors like rivastigmine can cause bradycardia.

Caffeine is a commonly used supplement and is found in many food and beverages. I discuss caffeine pharmacology, adverse effects, and drug interactions. Caffeine can inhibit CYP1A2 and also be affected by CYP1A2 inhibitors. I discuss some examples in the podcast. It is critical to inquire about caffeine intake when patients are reporting insomnia. Caffeine has been associated with increases in pulse and blood pressure. Be sure to ask about caffeine intake when assessing these vital signs.

Colestipol is a bile acid sequestrant that can be used in the management of hyperlipidemia. By binding bile acid in the gut, colestipol can lower LDL that is bound to bile acid by eliminating it through the feces. Numerous drug interactions existed as colestipol can bind many drugs. This is a downside to its use and why it isn't a preferred hyperlipidemia agent. In patients with elevated triglycerides, colestipol should be avoided.

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.