Suppositories with observed

In The literature there are a number of publications on the rectal administration of Nitrofurantoine. But these are very old so they are not available electronically.
of an article I can find the abstract and I take this text.

Rectal Absorption of nitrofurantoin
Eugene L. Parrott *, Lloyd E. Matheson Jr.
College of Pharmacy, University of Iowa, Iowa City, IA 52242

The absorption in humans of nitrofurantoin from seven suppository bases was studied using Urinary excretion measurements. Rectal absorption was alley than GI absorption. The administration of 400 mg or nitrofurantoin in a polyethylene glycol-polysorbate 80 suppository base and in a polyethylene glycol-silica suppository base provided an adequate urinary concentration of nitrofurantoin. Persons who cannot tolerate orally administered nitrofurantoin due to gastric upset could receive nitrofurantoin therapy rectally.

apparently, the rectal absorption is less good as the oral, so a dose increase can be foreseen. So eg 30mg instead of 20mg.

as suppository Mass is pointed towards a PEG base with addition of BV Polysorbaate 80 (1%). You could also try Suppocire AS2X, which is a suppository mass, which contains Tween 80, and is prescribed for difficult absorption.

to conclude, it seems recommendable to determine the urinary concentrations of observed or to determine the efficacy of the administered suppositories via another possible bacteriological technique. If this Is insufficient then a further adjustment of the dose can happen.