Urinary tract infections in women of child bearing age and in the elderly are one of the most common problems

Common pathogens Escherichia coli Staphylococcus saprophyticus Klebsiella pneumoniae Proteus mirabilis

These infections may be treated with any one of a group of agents called UTA.

These drugs do not achieve antibacterial levels in the circulation, but because they are conc.in the urine, microorganisms at that site can be effectively eradicted.

It must decompose at an acidic pH of 5.5 or less in the urine

Thus producing formaldehyde, which is toxic to most bacteria

The reaction is slow, requiring 3 hours to reach 90% decomposition

Bacteria do not develop resistance to formaldehyde

Methenamine is frequently formulated with weak acid such as mandelic acid or hippuric acid, which lowers the pH of urine, thus aiding decomposition of the drug

Administered orally It is distributed throughout the body

fluids But no decomposition of the drug

occurs at pH 7.4, thus systemic toxicity does not occurs.

The drug is eliminated in the urine

Gastrointestinal distress In higher doses Albuminuria Hematuria Rashes

In patients with renal insufficiency[mandelic acid accumulates in blood-acidosis]

In patients with hepatic insufficiency[the released ammonia is not detoxified—CNS toxicity]

Sulfonamide[antagonism]

It is nitrofuran derivative It is less commonly employed for

treating UTIs because of its narrow antimicrobial spectrum and its toxicity

It blocks bacterial carbohydrate metabolism by inhibiting its acetyl CoA synthesis.

Sensitive bacteria reduce the drug to an active agent,nitroanion superoxide and other toxic reactive intermediates which damage bacterial DNA

It is primarily bacteriosatic but acts as bactericidal in higher conc. and in acidic urine

It loses its antimicrobial action at pH 8. Acidifying agents such as vit C and

cranberry juice increases its effectiveness.

Primarily active against gram negative bacteria[E.coli and proteus mirabilis].

Some extant gram positive organisms such as staphylo.aureus and enterococcus faecalis

Gastrointestinal disturbances—nausea, vomiting, epigastric pain, diarrhoea

An acute reaction with chills, fever and leucopenia[occasionally]

Peripheral neuritis [long term use] Haemolytic anaemia[G-6-PD]] Liver damage[hepatitis], pulmonary

reaction with fibrosis[chronic use] Urine becomes dark brown on exposure

to air

Cotrimoxazole Beta lactam antibiotics Aminoglycosides Tetracyclines Chloramphenicol

Better in acidic urinary pH

Nitrofurantoin Tetracyclines Methicillin Cloxacillin

Better in alkaline urinary pH

Cotrimoxazole Gentamicin Cephalosporins FQs

Urinary pH is immaterial—nalidixic acid, chloramphenicol, ampicillin

It is an orange dye which exerts analgesic effects in UTIs and provides symptomatic relief from burning sensation, dysuria and urgency due to cystitis.

It is devoid of antibacterial activityADR:-Nausea, epigastric distress, urine

colour turns orange red due to its metabolite.

USES:-urinary tract analgesic[200mg TDS]