Interesting scripts

[Jeff]

Originally Posted by admin

I once worked for a week where one of the local GP's prescribed amoxicillin QDS and ampicillin TDS.

The difference between ampicillin and amoxicillin is mainly one of licencing - as the patent on qds Penbritin (ampicillin) came too an end the new wonder antibiotic Amoxil was introduced with a tds dosage.

Amoxicillin half life 61.3 minutes
http://en.wikipedia.org/wiki/Amoxicillin

Ampicillin half life approx 1 hour
http://en.wikipedia.org/wiki/Ampicillin

Jeff

[Steve G]

Originally Posted by Jeff

The difference between ampicillin and amoxicillin is mainly one of licencing - as the patent on qds Penbritin (ampicillin) came too an end the new wonder antibiotic Amoxil was introduced with a tds dosage.

Amoxicillin half life 61.3 minutes
http://en.wikipedia.org/wiki/Amoxicillin

Ampicillin half life approx 1 hour
http://en.wikipedia.org/wiki/Ampicillin

Jeff

But half life is only part of the story, bioavailabilty is also important (95% for amoxicillin against 40% for ampicillin), as is volume of distribution and minimum inhibitory concentration.

Surely the licencing wouldn't be different unless there was a good reason for it, and given that amoxicillin is effective at a tds dose, why give it qds?

[Zoggite]

What about spectrum of activity? Salmonella is more sensitive to amoxicillin than to ampicillin, but it's the other way around for Schigella...

[Jeff]

Originally Posted by Steve G

Surely the licencing wouldn't be different unless there was a good reason for it,

The patent on Penbritin was soon to expire and its replacement Amoxil needed to offer an advantage in order to generate sales.

and given that amoxicillin is effective at a tds dose, why give it qds?

No reason at all, but neither expensive nor dangerous enough to worry about.

Jeff