Nitrofurantoin

ST. LOUIS--A 7-day course of nitrofurantoin is hard to beat for cystitis in women, according to Dr. Sebastian Faro, professor of ob.gyn. at the University of Texas, Houston.

"I'll be honest with you. This drug is my favorite. At 100 mg q.i.d., it's well tolerated. Tissue levels are nonexistent, blood 1evels are low. You get very high levels in the urine. And nitrofurantoin doesn't affect the vaginal flora," he said at the 12th International Pelvic Reconstructive and Vaginal Surgery Conference.

A particularly attractive feature of nitrofurantoin in postoperative patients is that the drug won't mask soft-tissue infection, bacteremia, or respiratory tract infection.

This is a drug, however, that has to be given for a full 7 days. There is no persuasive evidence that shorter courses are adequate for cystitis, Dr. Faro said at the meeting, which was sponsored by the Society of Pelvic Reconstructive Surgeons.

Nitrofurantoin is active against Escherichia coli, the cause of most cases of cystitis. That's crucial, since roughly 40% of all isolates of E. coli are now ampicillin resistant and 20% show resistance to trimethoprim-sulfamethoxazole.

Nitrofurantoin also has good activity against Enterobacter, Streptococcus, Staphylococcus, Enterococcus, and Klebsiella. It is definitely not active against Proteus or Pseudomonas. However, Pseudomonas cystitis is unlikely, except in a chronically catheterized patient who has been in an ICU.

One of nitrofurantoin's best qualities is that it is urine specific. It doesn't exert selective pressure on bacteria located in other bodily ecosystems; hence it doesn't promote bacterial resistance.

This is a good drug for use in pregnancy, since it doesn't reach the fetus. Nearly 100% of isolates of group B strep are sensitive to nitrofurantoin.

Dr. Faro urged his colleagues to stay away from empiric use of antibiotics that can select for resistant bacterial strains.

"Basically, I'm talking here about staying away from [beta]-lactam antibiotics. You shouldn't automatically go the first time around to the cephalosporins or penicillins without a specific indication. And please, please try not to use the quinolones. I know everybody likes ciprofloxacin, but if you look at what's happened to Cipro, it's become a lesser and lesser drug because resistance is developing," the infectious disease specialist said.

Macrodantin, a macrocrystal formulation, is the most widely prescribed and best tolerated form of nitrofurantoin. The most common adverse effects are GI upset and headache.

Fosfomycin (Monurol) is an effective single-dose drug for acute cystitis due to E. coli or Enterococcus faecalis. It is given as a sachet containing the equivalent of 3 g of fosfomycin. Multiple dosing is not recommended.

A seldom-used drug with good efficacy as chronic suppressive therapy in patients with an indwelling catheter is methenamine. This urinary antiseptic is active against all gram-positive and gram-negative bacteria causing bacteriuria. It has virtually no resistance potential. But methenamine is not aggressively promoted, and when Dr. Faro requested a show of hands as to who in the audience of hundreds of physicians had ever used it, only a single hand went up.

In the presence of urine acidified by administration of ascorbic acid at 1 g q.i.d., methenamine is hydrolyzed to form formaldehyde, which kills the bacteria without selecting for resistance.

Dr. Faro said that he has no financial ties to the makers of any of these anticystitis drugs.

COPYRIGHT 2002 International Medical News Group
COPYRIGHT 2002 Gale Group