1. PHL424 ANTIBACTERIALS Dr. Sarah I bukhari Pharmaceutics microbiology Department College of Pharmacy King Saud University PHL424 DNA inhibitors 1 12/12/2015

2. ANTIBIOTIC CLASSES  Inhibit cell wall synthesis  β -lactams  Glycopeptides  Bacitracin  Fosfomycin  cycloseine  Inhibit protein biosynthesis  Aminoglycosides  Macrolides & Lincosamides  Oxazolidinones & Streptogramins  Tetracyclines & Chloramphenicol  Act on cell membrane  Polymyxins  Lipopeptides (Daptomycin)  Inhibit DNA synthesis  Sulfonamides  Trimethoprim  Quinolones  Metronidazole and Nitrofurantoin  Rifamycins 12/12/2015 PHL424 DNA inhibitors 2

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4. A-Quinolones MECHANISM OF ACTION Quinolone Target: 2 essential bacterial enzymes 1. DNA gyrase (The main target in Gram negative bacteria) 2. Topoisomerases IV (The main target in Gram +ve bacteria) DNA gyrase is responsible for supercoiling of DNA Composed of 2 GyrA & GyrB subunits, encoded by gyrA & gyrB. Quinolones interfere with DNA gyrase and prevent conversion of relaxed DNA to super-coiled DNA. Topoisomerase IV decatenates or removes the interlinking of daughter chromosomes. Composed of 2 subunits, ParC & ParE encoded by parC & parE Quinolones interfere with topoisomerse II & prevent decatenation of DNA 12/12/2015 PHL424 DNA inhibitors 4

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6. MECHANISM OF RESISTANCE 1. Chromosomal mediated A. Alterations in the targets of quinolones Single step mutation in DNA gyrase & topoisomerase IV High level of resistance was resulted due to Mutation in QRDR of DNA gyrase and topoisomerase II B. Decreased accumulations of drug inside bacteria i. Impermeability of the membrane and/or ii. Decrease in level of expression of OmpF in E. coli iii. An over-expression of efflux systems. 12/12/2015 PHL424 DNA inhibitors 6

7. MECHANISM OF RESISTANCE 2. Plasmid mediated quinolone resistance (PMQR) responsible for low level of resistance. PMQR detected only in Enterobacteriacae Three known PMQR mechanisms to date: A. Qnr determinants (qnrA, qnrB, qnrS, qnrD, qnrC) Protect DNA gyrase & topoisomerase IV from quinolone inhibition.(inhibit DNA binding) B. Aminoglycoside acetyltransferase (AAC(6)-Ib-cr). AAC(6)-Ib-cr is a variant of AAC(6)-Ib and is responsible for reduced susceptibility to ciprofloxacin or norfloxacin by N-acetylation of a piperazinylamine C. QepA (quinolone efflux pump) 12/12/2015 PHL424 DNA inhibitors 7

8. Correlation between MIC and QRDR mutations Single mutation in gyrA results in high-level resistance to nalidixic acid & reduce susceptibility to Fluoroquinolones To obtain high levels of resistance to fluoroquinolones, the presence of additional mutation(s) in gyrA and/or in another target such as parC is required MIC of nalidixic acid could be used as a generic marker of resistance for the quinolone in Gram- negative bacteria The most frequent mutation observed in quinolone- resistant E. coli is at codon 83 followed by 87 of gyrA In the parC gene of E. coli the most common substitutions occur at codons 80 and 84 12/12/2015 PHL424 DNA inhibitors 8

9. 12/12/2015 PHL424 DNA inhibitors 9 Pipemidic acid

10. Classification of quinolones 1st generations (Narrow spectrum) Nalidixic acid, oxolinic acid and pipemidic acid Nalidixic acid was introduced in 1962. Active against aerobic G -ve (Enterobacteriaceae). Pipemidic acid has extra activity against Ps. aeruginosa Disadvantages No activity against G +ve or anaerobic bacteria. Limited spectrum and poor tissue penetration Their use is restricted to treatment of UTI Toxicity especially to CNS and GIT Rapid emergence of resistance 12/12/2015 PHL424 10

11. CLASSIFICATION 2. 2 nd generation (Broad spectrum) Quinolones were a little-used drug class until the early 1980s when introduced 2 nd generation fluorination at 6-position  Fluoroquinolones (FQ) ring substituent (piperazine, methylpiperazine) at C7 FQ modification of other side chains led to: Improved activity against Gram negative (Enterobacteriaceae, Peudomonas, Acinetobacter, Haemophilis, Moraxella & Neisseria) Enhanced anti-Gram-positive activity Improved potency against pneumococcus Improved PK & longer serum half-lives Lack activity against anaerobic bacteria 12/12/2015 PHL424 DNA inhibitors 11

12. CLASSIFICATION 2. 2 nd generation (Broad spectrum) Nor-, Cipro-, Ofloxacin, Pefloxacin, Lomefloxacin NOR is the first 2 nd generation confined for treatment of UTI and STD because of low serum levels and poor tissue penetration CIPRO is the most common 2 nd generation CIPRO is the most potent quinolones against Gram- ve. CIPRO is alternative to parenterally antibiotics for the treatment of osteomyelitis caused by susceptible organisms due to its good penetration into bone Of the 2 nd generation, Ofloxacin has the greatest activity against Chlamydia trachomatis treatment of complicated UTI, pyelonephritis, STD, selected pneumonias and skin infections 12/12/2015 PHL424 DNA inhibitors 12

13. CLASSIFICATION 3. 3 rd generation (Expanded spectrum) Levo-, Gatifloxacin, Sparfloxacin, Grepafloxacin. In 1990s, 3 rd generation was introduced. expanded activity against gram-positive organisms, particularly S. pneumoniae has activity against mycoplasma, Chlamydia, legionella has good activity against anaerobic bacteria. less active than ciprofloxacin against Pseudomonas 4 th generation (Extended spectrum) Trovafloxacin, Moxifloxacin, Gemifloxacin. In 2000s, 4 th generation was introduced. Has potent activity against anaerobes and increased activity against pneumococci 12/12/2015 PHL424 DNA inhibitors 13

14. PHARMACOKINETIC S taken orally: well absorbed from GIT-bioavailability of≥ 50% Some FQ’s are available parenterally/ophthalmic Newer FQ’s have longer serum half-lives than ciprofloxacin allowing for once daily dosing CIPRO: 500 – 750 mg q 8-12h LEVO:500-750 mg q24h MOXI: 400mg q24h achieve high intracellular concentrations (e.g. PMNs) widely distributed in body tissues (except CNS). Elimination: most are eliminated by the kidneys (unchanged & as metabolites), although some are eliminated by the liver 12/12/2015 PHL424 DNA inhibitors 14

15. Approved clinical uses for selected fluoroquinolones. Vincent T. Andriole Clin Infect Dis. 2005;41:S113-S119

16. CLINICAL USE Empiric therapy of CAP (community-acquired pneumonia) Oral therapy of un-/complicated UTI or RTI Oral therapy of serious infections such as osteomyelitis, pneumonia or soft tissue infections Treatment of STD: gonorrhea, chancroid, chlamydial urethritis Empiric therapy of travelers diarrhea Treatment of typhoid Therapy for multidrug-resistant tuberculosis 12/12/2015 PHL424 DNA inhibitors 16

17. SIDE EFFECTS Generally very safe antibiotics which do not cause serious or life-threatening adverse reactions The most frequent side-effects are: GIT(nausea, dyspepsia, vomiting) CNS reactions such as dizziness, insomnia, headache Should not be used in children and in pregnancy Drug interactions: ↓ absorption: Al 3+, Mg 2+ and Ca 2+ antacids CYP450 inhibition potential drug interactions for ciprofloxacin (Ex) can increase warfarin exposure (real changes in INR are rare, but monitor) 12/12/2015 PHL424 DNA inhibitors 17

18. B. Nitroimidazoles and nitrofurans METRONidazole (Prodrug): 5-nitroimidazole derivative Specifically active against anaerobic organisms. Effective against protozoa: E. histolytica, Giardia lamblia. Mechanism of Action Antimicrobial action is due to unstable metabolites produced by reduction inside anerobic bacteria after uptake Nitro gp converted to nitrite radical by low redox potential. Metabolites covalently bind to DNA, disturb its helical structure, fragmentation of microbial chromosome Finally inhibit nucleic acid biosynthesis  bacterial death Resistance to metronidazole does not occur. 12/12/2015 PHL424 DNA inhibitors 18

19. MECHANISM OF ACTION 12/12/2015 PHL424 DNA inhibitors 19

20. PHARMACOKINETICS Well absorbed orally T max is 1- 2 h, and C max is 25 mg/mL. Oral bioavailability is not affected by food, but peak serum levels will be delayed to 2 h. Metronidazole appears in CSF, saliva, and breast milk in concentrations similar to those found in plasma. Less than 20% is protein bound. Elimination is via urine (60% to 80%) & feces (6%-5%) half-life is 8 h and the hydroxy-metabolite half-life is 15 h Decreased renal function does not alter single-dose pharmacokinetics of metronidazole Hepatic Function Impairment: PO/IV Use lower doses cautiously and close monitoring of plasma metronidazole levels and toxicity is recommended 12/12/2015 PHL424 DNA inhibitors 20

21. DOSAGE AND ADMINISTRATION  Anaerobic Bacterial Infections Give IV initially when treating most serious anaerobic infections. IV infusion: 15 mg/kg over 1 h (1 g for 70 kg adult); then a maintenance dose of 7.5 mg/kg over 1 h every 6 h (500 mg for 70 kg adult). Do not exceed 4 g in 24 h. For prophylaxis, loading dose is to be completed 1 h before surgery, followed by maintenance dose 6 & 12 h later. Flagyl 750 ER, 500, 375, 250 mg tablets; Injection, solution 5 mg/mL 7.5 mg/kg (500 mg for 70 kg adult) every 6 h (max, 4 g/24 h) for 7-10 days. Children dose: PO 5 mg/kg/dose 3 times daily for 7 days 12/12/2015 PHL424 DNA inhibitors 21

22. SIDE EFFECTS Nausea, Vomiting, epigastric distress, abdominal cramps oral thrush Metallic taste 12/12/2015 PHL424 DNA inhibitors 22

23. B. Nitroimidazoles and nitrofurans NITROFURANTOIN is used in the treatment of UTI. Antibacterial levels are not reached in the blood and the drug is concentrated in the urine. NITROFURAZONE is used mainly as a topical agent in the treatment of burns and wounds and also in certain types of ear infections. 12/12/2015 PHL424 DNA inhibitors 23

24. RIFAMYCINS Natural and semi-derived from filamentous soil bacteria Complex macrocyclic antibiotics Members of the class Rifabutin Rifapentine Rifampin = rifampicin (The most common used) 12/12/2015 PHL424 DNA inhibitors 24

25. C. RIFAMPIN (RIFAMYCIN) Bactericidal broad spectrum antibiotic. Bactericidal (aerobic & anaerobic Gram+ve cocci) Bacteriostatic (enterococci) Very effective in treatment of tuberculosis. Penetrates well into CSF Treatment of tuberculous meningitis Active against N. gonnorhea, N. meningitis, H. Influenzae. It is frequently used in prophylaxis of meningitis Active against Enterobacteriaceae. Inhibits Brucella sp. and Coxeilla burnetti intracellularly. 12/12/2015 PHL424 DNA inhibitors 25

26. MECHANISM OF ACTION  Inhibits DNA-dependant RNA polymerase.  Forms a stable complex with DNA dependant RNA polymerase.  Binds to  -subunit of the core enzyme of RNA polymerase & blocks the action of the enzyme at initiation stage of transcription.  Prevents the initiation stage of transcription.  Doesn’t inhibit transcription once it has been initiated.  Does not affect mammalian RNA synthesis. 12/12/2015 PHL424 DNA inhibitors 26

27. MECHANISM OF RESISTANCE  Resistance to rifampicin develops quickly.  Rifampin-Resistant isolates posses an altered DNA-dependant RNA polymerase, which arises easily by single step mutations during therapy.  missense mutations in the rpoB gene 12/12/2015 PHL424 DNA inhibitors 27

28. PHARMACOKINETIC Rapid & complete absorption after oral administration. Absorption is improved when taken on an empty stomach Wide distributed into most body tissues & fluids including CSF It concentrates intracellularly up to five times that of extracellular concentrations, primarily in PMN. The protein binding of rifampin is approximately 80 %. Rifampin undergoes extensive hepatic metabolism to less active metabolites, with a half-life of 3 hours. Renal elimination of unchanged drug is minimal (<30 %); thus, no dose adjustments are required in renal insufficiency. Caution should be used when rifampin is administered to patients with significant hepatic disease, especially when used in combination with other hepatotoxins, such as isoniazid. 12/12/2015 PHL424 DNA inhibitors 28

29. DOSING AND ADMINISTRATION For treatment of TB is 10 mg/kg (maximum 600 mg daily) given daily or either twice or three times weekly by DOT. IV doses are similar to those administered orally. Oral doses should be administered 1 h before or 2h after meals. The therapeutic range for rifampin against M. tuberculosis is a two-hour post-dose concentration of 8 to 24 microgram/mL No dose adjustments are needed for renal dysfunction or dialysis 12/12/2015 PHL424 DNA inhibitors 29

30. ADVERSE EFFECTS Gastrointestinal effects (nausea, vomiting, diarrhea), CNS effects (headache, fever) Dermatologic effects (rash, itching, flushing) Hematologic effects (thrombocytopenia, neutropenia, and acute hemolytic anemia) Hepatitis is infrequently associated with rifampin Patients should be advised that rifampin typically causes an orange or red-orange discoloration of body fluids (including urine, sweat, saliva, and tears) 12/12/2015 PHL424 DNA inhibitors 30

31. DRUG INTERACTIONS Decreases half life of many drugs by inducing CYPs cytochrome P450 isoenzyme CYP3A4 Potentially decreasing serum concentrations of co- administered drugs. oralcontraceptives,corticosteroids, cyclosporine, war farin, phenytoin, theophylline, azole antifungals, oral hypoglycemics, verapamil, beta-blockers & HIV protease inhibitors as well as the nonnucleoside reverse-transcriptase inhibitors is not recommended. 12/12/2015 PHL424 DNA inhibitors 31