Manufacturing Process

A mixture containing 1.33 g of 5,8-dihydro-8-ethyl-2-methylthio-5oxopyridol[2,3-d]pyrimidine-6-carboxylic acid, 1.94 g of piperazine hexahydrate and 20 ml of dimethyl sulfoxide was heated at 110°C for 1 hour with stirring. The separated solid was collected by filtration, washed with ethanol, and then dried at such a temperature that did not rise above 50°C to give 1.57 g of the trihydrate of the product as nearly colorless needles, MP 253° to 255°C.The starting material may be produced by reacting 6-amino-2methylthiopyrimidine with ethoxymethylene malonic acid diethyl ester. The intermediate thus produced is converted by boiling in diphenyl ether to 6ethoxycarbonyl-2-methylthio-5-oxo-5,8-dihydropyrido[2,3-d]pyrimidine. That is hydrolyzed by sodium hydroxide to cleave the ethoxy group and then ethylated with diethyl sulfate to give the starting material.

Therapeutic Function

Antibacterial (urinary)

Pharmaceutical Applications

An orally administered pyridopyrimidine derivative with a 7-piperazinyl moiety. The piperazinyl moiety at C-7 increases in-vitro activity against Ps. aeruginosa. Pipemidic acid is inactive against Gram-positive bacteria or anaerobes It is well absorbed orally. The drug is rapidly metabolized, primarily to acetyl, formyl and oxo derivatives, which exhibit much reduced antibacterial activity. It is eliminated in the urine, 50–85% of a dose appearing over the first 24 h, less than 2% as inactive metabolites. Non-renal clearance accounts for 10–40% of a dose in the young, rising to 40–70% in elderly subjects, thereby compensating for possible renal insufficiency. No dosage adjustment is necessary in patients with mild renal insufficiency. Some of the drug is eliminated in the bile and a significant portion appears in the feces. Nausea and vomiting are common; dizziness, weakness and grand mal seizures have been observed, principally in the elderly. A number of reactions have been sufficiently severe to require discontinuation of therapy. Clinical use is restricted to urinary tract infections.

Biochem/physiol Actions

Pipemidic acid modulates (inhibits) bacterial DNA gyrase-dependent processes such as DNA polymerization, (ATP-dependent) DNA supercoiling, and chromosome fragmentation. Pipemidic acid has been shown to induce inhibition of lymphocyte DNA synthesis.

Definition

ChEBI: A pyridopyrimidine that is 5-oxo-5,8-dihydropyrido[2,3-d]pyrimidine-6-carboxylic acid substituted at position 2 by a piperazin-1-yl group and at position 8 by an ethyl group. Used for treatment of gastrointestinal, biliary, and urinary infecti ns.