What's the difference between the many erythromycin forms?

[crossurfingers]

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It comes as erythromycin base, erythromycin stearate, and erythromycin ethylsuccinate. If a doctor writes a prescription for erythromycin, is there one that you generally default to or do you have to call to clarify? I only remember my password to Lexicomp and it didn't give me too much detail as to the differences between forms except that it takes 400mg of erythromycin ethylsuccinate to equal the same blood levels that 250mg of erythromycin stearate or base produces.

Also, does anyone know the general differences between the different forms of doxycycline as well?

Thanks in advance!

 

[Glycerin]

The estolate salt form should be avoided in pregnant women due to an increased risk of hepatitis. I think all of these are off the market now, though.

 

[RxWildcat]

There are several salt forms of ery that have been formulated to try and overcome the poor bioavailability of ery. The different salts all have different bioavailabilities. Stearate preps are susceptible to gastric acid, and estolate preps are more acid stable. Ethylsuccinate preps are absorbed first and then hydrolyzed in the blood to free erythromycin.