(From Lippencott’s, by Brian Buschman)
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Sulfa drugs are PAGA alanogues. Since cells cannot uptake folic acid it must be synthesized from PABA. Sulfa drugs block that process.
Spectra covers enterobacteria, PCP, Chlamydia and Nocardia. They are used for these and for recurrent UTI (since most are colonic bacteria). Sulfas are DOC for AIDS patients with PCP infections.
Resistance follows one of three patterns:
1) Altered enzymes are less interested in sulfa and want real PABA.
2) Decreased uptake.
3) Increased PABA synthesis in the cells.
Sulfonamides are usually given PO and are absorbed well except for sulfasalazine which is not absorbed at all. This makes sulfasalazine a DOC for inflammatory bowl disease.
They distribute well everywhere. They are metabolized in the liver and are excreted by the kidneys. Sulfasalazine is not absorbed so it cannot be metabolized by the liver. It is metabolized by colonic bacteria. The metabolizes cause anti-inflammatory effects and are then deficated.
Adverse effects include:
1) Crystalluria develops and leads to nephrotoxicity. Crystalluria is less at higher pH.
Do NOT give sulfa drugs to a patient on methenamine for UTIs.
Dihydrofolate reductase makes purines and pyramidines. Trimethoprim is a broad spectrum antibiotic that is preferentially bound to dihydrofolate reductase which blocks it.
It has a similar spectrum to sulfomamides treating recurrent UTS, Chlamydia, E coli and such. It is stronger than sulfas but can be used in combination.
They go everywhere like the sulfas. They do cause signs of floate deficiency like megaloblastic anemia, granulocytopenia, etc. You must give your patient folinic acid which goes into human cells but not bacterial ones.
The combo of trimethaprim and sulfamethoxazole has less resistance and stronger antimicrobial effects because it inhibits folate in two ways.
Adverse effects include effects of both drugs but shows prolonged PATIENT in warfarin patients and Pneumocystis in HIV patients.
Flouroquinolones, like ciprofloxacin, exnxacin, lomeflozacin and other “xacins.”
Fluoroquinolones inhibit DNA gyrase therefore messing up DNA replication. Resistance is common in gram + because they alter the target site and decrease accumulation of the drug.
The main stectrum is against gram 0 and is also used in AIDS patients. They have a poor activity against gram + and anaerobes.
They distribute poorly to the CSF, vagina and prostate. One good fact is that they concentrate in macrophages so they are effective against lefionella and other intracellular organisms.
They are excreted. Some are metabolized first and some are not.
Adverse effects of flouroquinolens are similar to those of nalidixic acid and includes:
1) Phototoxicity
2) CNS disturbances
3) Drug interactions with antacids (decreased absorption) and increased theophylline levels.
Nalidixic acid is similar to fluoroquinolones just older. It is used for some UTIs. It has hepatotoxicity if used for more than two weeks.
Metronidazole is an electron acceptor that makes radicles that mess up DNA synthesis. It works on parasites and bacteria.
It is unsed in bacteria for C. difficile, B. fragilis and as part of the BMT for H. pylori.
It is also used as DOC for parasites like T. vaginalis, Giardia and amebiases.
There is no real resistance. It is well absorbed and goes everywhere.
It is ultimately metabolized by mixed-function oxidases, glucuronated and excreted. Drugs like phenobarbital enhance metabolism and drugs like cimetidine inhibit it. Adverse effects are few but usually are related to GI disturbances.
H. pylori is the main cause of GUD and DUD and is not killed by single drugs. The most common treatment includes:
1) BMT – Bismuth subsalicylate, metronidazole & tetracycline.
2) BMT-O – Bismuth subsalicylate, metronidazole, tetracycline and omeprazole (a H+ pump inhibitor).
3) CT – Clarithromycin and tritec. Remember clarithromycin inhibits protein synthesis.
4) COA – Clarithromycin, omeprazole and amoxacillin. Remember amoxacillin is an extended spectrum penicillin.
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