Many of us prescribe medication to be taken BID or TID often, without really thinking it through; it is a sort of a habit. However, for medications with shorter half-lives, this dosing pattern may not be effective or optimal.
An example: If you prescribe Bob some carvedilol 12.5 mg BID, he might choose to take it at 7 am and around 4 pm. While this dosing pattern isn’t terrible, it allows for a dip in blood level around 4-5 am. Carvedilol has a half life of 6-10 hours, so if Bob’s last dose is taken at 4 pm, by 4 am, over half the active medicine has been used, leaving decreased blood levels for the next couple of hours.
Why is this a problem? Because, for carvedilol, specifically, its use may be dysrhythmia control. However, as the body awakens in the morning, there is a strong stress placed on the heart to increase work and fund the body with adequate oxygenation. This demand from the body creates a bit of a stressor which COULD trigger dysrhythmias, especially if the available carvedilol is less than optimal.
This kind of effect can happen with a variety of medications, whether prescription or over the counter. So, it can be quite helpful to teach patients to spread meds out, around the clock.
I typically write BID meds for Q12 hours, instead…
Or TID meds, I write Q8 hours.
I also often take a moment to explain this concept to patients, helping them understand why they should take their medication around the clock, rather than at prescheduled meals. For meds that might need food intake, I just tell them to have a bite or two with the doses that need to be taken away from a meal.
So, take into account the half lifes and pharmacology of the medications you prescribe. UNDERSTAND these 2 concepts, and it will make you a better nurse practitioner!
Additonally, patients really appreciate learning these little tips, that are seemingly negligible, but they might mean the difference between symptom resolution or not.