Dutasteride (Avodart) is a 5-alpha-reductase inhibitor. I discuss the pharmacology, adverse effects, and drug interactions on this podcast.
Dutasteride reduces the size of the prostate over time. It takes a significant amount of time to provide symptom relief (usually at least 3-6 months).
Dutasteride is broken down by CYP3A4 to a minor extent which means that strong CYP3A4 inhibitors may increase drug concentrations.
When using dutasteride for BPH, remember to review the medication list for drugs that can cause urinary retention such as anticholintiercs and alpha-agonists.
On this episode, I discuss tolterodine pharmacology, adverse effects, and drug interactions.
Tolterodine (Detrol) is an anticholinergic medication used to manage the symptoms of overactive bladder.
Tolterodine’s anticholinergic activity can lead to a significant number of adverse effects like dry mouth, dry eyes, constipation, and urinary retention.
Elderly patients may be at greater risk for anticholinergic adverse effects from tolterodine compared to younger patients.
Tolterodine can have additive effects from other anticholinergics like diphenhydramine or TCAs which enhance its potential for side effects.
On this episode, I discuss trospium pharmacology, adverse effects, and important drug interactions you should know.
Trospium chloride (Sanctura) is a bladder antimuscarinic or anticholinergic. It blocks the action of acetylcholine in bladder smooth muscle. It is used for urinary frequency and overactive bladder. The immediate-release formulation is taken twice a day. There is an extended-release version that is more expensive.
As its classification suggests it is going to have anticholinergic effects that include dry eyes, dry mouth, constipation, urinary retention, GI tract slowing down, CNS sedation, and increased risk of falls. Compared to older bladder anticholinergics such as oxybutynin or tolterodine there is less CNS penetration. Hopefully, this will cause the patient to experience fewer CNS side effects. A downside to this being a newer medication is that it costs more.
Trospium is on the BEERS list. Look for medications started after the trospium that indicate anticholinergic side effects such as saliva substitutes, an increase in BPH medications, artificial tears, or constipation medications.
It should be administered on an empty stomach as food can block absorption. If the patient is currently taking it with food and seeing results there is no need to change how they are taking it.
Trospium is not metabolized by CYP enzymes minimizing drug interactions. Most interactions occur because of additive effects. Avoid using it with other medications on the BEERS list, especially other anticholinergic medications. Be cautious using other medications with sedative effects and CNS depression (benzodiazepines, sleep medications, opioids, alcohol) as they may have additive effects.
Calcium Acetate (PhosLo) is used in the management of hyperphosphatemia associated with CKD.
Important monitoring parameters for calcium acetate include phosphorus, calcium, PTH, and renal function.
There are numerous binding interactions with calcium acetate. It can reduce concentrations of some HIV drugs, antibiotics, and thyroid supplements. I discuss more examples in the podcast.
Thiazide diuretic in combination with calcium acetate may increase the risk for hypercalcemia.
Mirabegron is a beta-3 agonist that can help relax bladder smooth muscle and manage symptoms of overactive bladder.
Mirabegron inhibits CYP2D6 which can negatively impact the effectiveness of tamoxifen. I discuss this in greater detail in the podcast.
Tramadol and codeine effectiveness can be impacted by mirabegron. Be aware of this when using this medication.
By inhibiting CYP2D6, mirabegron can increase the concentrations of many psychotropic medications such as fluoxetine, aripiprazole, clozapine, and paroxetine. I discuss this further in this episode of the podcast.
