question about precription dosing

[CalliopeDVM]

I'm a veterinarian but have a question about how doctors write prescriptions for their patients, because I've realized it's different than the current thought in veterinary medicine in a specific way. I'm afraid if I asked my doctor, I'd get an "this is how I do it" answer, without really thinking about why. So, if you were taught a certain way or have any information to add, I'd be interested:

Generally, we have been taught to stop prescribing medication based on how many times a day to give it, and instead prescribe it based on how many hours apart to give it. That's based on the metabolism of the drug and the benefit of not allowing the blood concentration to fall too low. So, I would prescribe a 3-times-a-day drug to be given "every 8 hours", not "three times a day", though I might verbally tell them to get as close to q8h as they can without getting up in the middle of the night. If I prescribe a once-a-day drug, I tell them to give it "once every 24 hours (once a day)".

I've noticed human doctors don't do that.

Is it because they think that type of instruction will decrease compliance because it's somehow too complicated? Or do they think that taking the medication every 8 hours is no more efficacious than taking it at any 3 times in 16 hours? Maybe it is, maybe it isn't -- I don't know and that's why I'm asking. Maybe vets are too anal about being precise on these things.

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[mvenus929]

I try to avoid writing prescriptions for more often than BID (twice daily) because it decreases compliance.

There are also some medications where the peak is far more important than the trough, so how far apart the dosing is isn't really a concern.

 

[DBV]

Seems like more of a question for a pharmacist

 

[CalliopeDVM]

Seems like more of a question for a pharmacist

No, because it's the doctors who actually write the prescriptions - why do they choose to prescribe something twice a day instead of every 12 hours?

 

[Stagg737]

No, because it's the doctors who actually write the prescriptions - why do they choose to prescribe something twice a day instead of every 12 hours?

Imo it's semantics because patients will assume Q12h just means twice a day and take it whenever they want anyway. In reality, physicians can only give recommendations and instructions. Compliance is completely up to the patients, many of whom will work taking medicine into their schedules, not adjust their schedules based on when they're supposed to be taking their meds.

 

[The Physician Philosopher]

Imo it's semantics because patients will assume Q12h just means twice a day and take it whenever they want anyway. In reality, physicians can only give recommendations and instructions. Compliance is completely up to the patients, many of whom will work taking medicine into their schedules, not adjust their schedules based on when they're supposed to be taking their meds.

I disagree. In my realm (acute pain) the difference between TID and q8 can be deadly. If someone receieves three doses of a long acting opioid in the 14 hours they are awake versus taking the med Q8, the dose can stack and lead to badness.

I agree with the above the more than BID dosing reduces compliance. That said, with certain drugs it really does matter. Patient education is requisite (not that it always computes)

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[CalliopeDVM]

I try to avoid writing prescriptions for more often than BID (twice daily) because it decreases compliance.

There are also some medications where the peak is far more important than the trough, so how far apart the dosing is isn't really a concern.

Thanks for that information - makes sense to me. I agree that more frequently than BID decreases compliance; I usually only do that for eye meds. I'm on a TID dose of clindamycin, and I'm finding taking it with food q8h along with inhaled meds that are q12h is not easy. Good thing I'm so sick that I have not much else to do but manage my meds for a week.

 

[Stagg737]

I disagree. In my realm (acute pain) the difference between TID and q8 can be deadly. If someone receieves three doses of a long acting opioid in the 14 hours they are awake versus taking the med Q8, the dose can stack and lead to badness.

I agree with the above the more than BID dosing reduces compliance. That said, with certain drugs it really does matter. Patient education is requisite (not that it always computes)

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I agree with all of that, but my point was regarding the bolded. You can tell a patient to take Q8h, but from my experience many aren't going to take it on that schedule religiously. They'll do what you initially said and take it 3 times during the 12-14 hours they're awake/when it's convenient for their schedule.

 

[CherryRedDracul]

I agree with all of that, but my point was regarding the bolded. You can tell a patient to take Q8h, but from my experience many aren't going to take it on that schedule religiously. They'll do what you initially said and take it 3 times during the 12-14 hours they're awake/when it's convenient for their schedule.

This is what they tend to do. If a medication doesn't have a narrow enough therapeutic index, then I might tell a patient to just take it TID rather Q8 unless I know they're religiously compliant.