Why Isn’t There Time-Released Propecia?
Hi Dr.,
You often mention how the half-life of finasteride is not so long. Why can’t you make it longer so that the dose is distributed over a week, rather than a day, and you could just take one pill per week? Many drugs are “extended release,” no?
I think taking a pill once a day is not too difficult for most people, but I don’t know if they’ve attempted making an extended-release pill.
For those who may not know how half life works, if you take a drug at 8am and the half life is 4 hours, at 12pm you will have 50% of the drug left in your blood stream, at 4pm you will have 25% left, at 8pm you will have 12.5% left, at 12 am you will have 6.25% left, at 4am you will have 3.125% left, at 8am (NEXT DAY 24 hours later) you will have about 1.5% left. Time to take another pill!
That’s too simplistic, Dr. Rassman – can you not suggest something else? How about taking 1.5 mg on Mondays, skip on Tuesdays, .85 mg on Wednesdays, 1.75 mg on Thursday’s, skip on Fridays, .25 mg on Saturdays, and then take .20 mg every three hours on Sundays? Lots of your readers are junior bio-chemists who love inventing new dosage schedules – 1 mg a day just doesn’t cut it for those folks…
Ok so taking 2.5mg doubles the amount in bloodstream all day long? Thus this is better than 1.25mg in morning and one at night?
Doubling a drug dose does not necessarily double the amount of drug in the bloodstream (depends upon absorption, elimination, distribution, etc). In addition, how long the biologic half-life of a drug is (as Dr R has nicely explained in his answer) is not the same as duration of action (Cialis has a 17.5 hr half-life but can work for a duration up to 36 hr). As S so humorously writes, why is everyone a closet biochemist! I would be inclined to take a drug in the dose and amount it is prescribed for the best effect (assuming I did not have a side effect)!