Pathways

Mercaptopurine is a purine antimetabolite prodrug that exerts cytotoxic effects via three mechanisms: via incorporation of thiodeoxyguanosine triphosphate into DNA and thioguanosine triphosphate into RNA, inhibition of de novo synthesis of purine nucleotides, and inhibition of Ras-related C3 botulinum toxin substrate 1, which induces apoptosis of activated T cells. Mercaptopurine travels through the bloodstream and is transported into cells via nucleoside transporters. Mercaptopurine is then converted to thioguanosince diphosphate through a series of metabolic reactions that produces the metabolic intermediates, thioinosine 5’-monophosphate, thioxanthine monophosphate, and thioguanosine monophosphate. Thioguanosine diphosphate is then converted via a thiodeoxyguanosine diphosphate intermediate to thiodeoxyguanosine triphosphate, which is incorporated into DNA. Thioguanosine diphosphate is also converted to thioguanosine triphosphate which is incorporated into RNA. The thioguanosine triphosphate metabolite also inhibits Ras-related C3 botulinum toxin substrate 1, a plasma membrane-associated small GTPase that regulates cellular processes, inducing apoptosis in activated T cells. Finally, de novo synthesis of purine nucleotides is inhibited by the methyl-thioinosine 5’-monophosphate metabolite, which inhibits amidophosphoribosyl-transferase, the enzyme that catalyzes one of the first steps in this pathway.

Meropenem is a carbapenem antibiotic used to treat a wide variety of infections in the body. Meropenem is a broad-spectrum carbapenem antibiotic. It is active against Gram-positive and Gram-negative bacteria. Meropenem exerts its action by penetrating bacterial cells readily and interfering with the synthesis of vital cell wall components, which leads to cell death. For use as single agent therapy for the treatment of the following infections when caused by susceptible isolates of the designated microorganisms: complicated skin and skin structure infections due to Staphylococcus aureus (b-lactamase and non-b-lactamase producing, methicillin-susceptible isolates only), Streptococcus pyogenes, Streptococcus agalactiae, viridans group streptococci, Enterococcus faecalis (excluding vancomycin-resistant isolates), Pseudomonas aeruginosa, Escherichia coli, Proteus mirabilis, Bacteroides fragilis and Peptostreptococcus species; complicated appendicitis and peritonitis caused by viridans group streptococci, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Bacteroides fragilis, B. thetaiotaomicron, and Peptostreptococcus species.Also for use in the treatment of bacterial meningitis caused by Streptococcus pneumoniae, Haemophilus influenzae (b-lactamase and non-b-lactamase-producing isolates), and Neisseria meningitidis. Its strongest affinities are toward PBPs 2, 3 and 4 of Escherichia coli and Pseudomonas aeruginosa; and PBPs 1, 2 and 4 of Staphylococcus aureus. Penicillin binding proteins are responsible for glycosyltransferase and transpeptidase reactions that lead to cross-linking of D-alanine and D-aspartic acid in bacterial cell walls.Inhibition of this protein leads to upregulation of autolytic enzymes and inhibition of cell wall synthesis. Meropenem is bactericidal and kills off the bacteria that it affects.

Metabolites of Meropenem are predicted with biotransformer.

Mesalazine is a non-steroidal anti-inflammatory drug (NSAID) structurally related to the salicylates. This molecule is used to treat mild to moderately active ulcerative colitis. Mesalazine's mechanism of action is still not understood, but it is believed that the molecule has a topical anti-inflammatory effect on colonic epithelial cells. It targets the prostaglandin G/H synthase-1 (COX-1) and prostaglandin G/H synthase-2 (COX-2) in the cyclooxygenase pathway. The cyclooxygenase pathway begins in the cytosol with phospholipids being converted into arachidonic acid by the action of phospholipase A2. The rest of the pathway occurs on the endoplasmic reticulum membrane, where prostaglandin G/H synthase 1 & 2 convert arachidonic acid into prostaglandin H2. Prostaglandin H2 can either be converted into thromboxane A2 via thromboxane A synthase, prostacyclin/prostaglandin I2 via prostacyclin synthase, or prostaglandin E2 via prostaglandin E synthase. COX-2 is an inducible enzyme, and during inflammation, it is responsible for prostaglandin synthesis. It leads to the formation of prostaglandin E2 which is responsible for contributing to the inflammatory response by activating immune cells and for increasing pain sensation by acting on pain fibers. Mesalazine inhibits the action of COX-1 and COX-2 on the endoplasmic reticulum membrane. This reduces the formation of prostaglandin H2 and therefore, prostaglandin E2 (PGE2). The low concentration of prostaglandin E2 attenuates the effect it has on stimulating immune cells and pain fibers, consequently reducing inflammation and pain. Furthermore, mesalazine also inhibits arachidonate 5-lipoxygenase, diminishing the inflammatory processes (leukotriene biosynthesis) and the peroxisome proliferator-activated receptor gamma (inhibiting transcription factors; NF-kappa-B-mediated proinflammatory responses). Mesalazine is administered as an oral tablet or as a rectal suppository.

Mesoridazine, the besylate salt of a metabolite of thioridazine, is a phenothiazine tranquilizer and a first generation typical antipsychotic. Based upon animal studies, mesoridazine, as with other phenothiazines, acts indirectly on reticular formation, whereby neuronal activity into reticular formation is reduced without affecting its intrinsic ability to activate the cerebral cortex.

Mesoridazine, the besylate salt of a metabolite of thioridazine, is a phenothiazine tranquilizer and a first generation typical antipsychotic. Based upon animal studies, mesoridazine, as with other phenothiazines, acts indirectly on reticular formation, whereby neuronal activity into reticular formation is reduced without affecting its intrinsic ability to activate the cerebral cortex.