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Acceptable lag between doses?

Mar 29, 2004

I have a simple yet important question. Because I work in retail, my work schedule constantly changes. I have chosen to take my once-a-day meds at a time of night when I am certain to be home, whether I work late or not. However, if there should ever be a time when I am unable to take my meds at exactly the time I have chosen, what would be considered an "acceptable lag" time between doses? For example, I take my meds at 11pm. If I miss the 11pm dose, how much time can pass before I take that missed dose without completely messing up my med schedule? Thank you for your help!

Response from Dr. Lee

This is a good question, but one that is difficult to answer in general. It depends on many factors, the most significant of which is what specific medications you are on. Generally there is not a truly "acceptable lag" time between doses. These medicines have been tested to see how long they remain in the blood or cells at levels that have been shown to be effective for most people. The testing is all based on averages. As you probably know an average is hard to apply to an individual because each individual may metabolize or clear the medicines at a different rate than others. Also, the medications may be metabolized differently by any one person depending on the time of day, what they may have eaten or had to drink that day, where they are in their hormonal cycle, if they have gained or lost weight recently, etc. The averages are approved by the FDA when they determine if a medication should be dosed every four,six, eight, twelve, or twenty-four hours.

So, your medicines have apparently been determined to be safe when dosed every twenty-four hours. Does that mean that dosing at twenty-six hours is unsafe? Not necessarily. However, in general it is best to hit as close as possible to the twenty-four. I usually advise folks to take the medicines within an hour window. If they must be early or late for some reason, it is better to overdose rather than underdose. In other words, it is better to take an extra dose than to skip a dose. With once a day dosing, that may mean moving the dose up and then gradually (over a few days) moving the dose back to the previous schedule. (Ex: If normal dosing is at 10:00PM, but one night it is important to dose a 7:00PM so as not to miss a dose. The following night it would be best to dose no later than 8:00PM, and at 9:00PM the night after, followed by a return to the 10:00PM dosing routine.)

I don't know if this is helpful for your specific situation. There are some medicines that stay in the system long enough to make it unnecessary to take the precautions I outline here. However, check with your doc on your particular meds.

Be well.

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