PM716 Pharmacology I Chapter 46 Sulfonamides PDF

PM716 Pharmacology I Chapter 46 Sulfonamides RMRocco, PhD 1  Oral Antibiotic Use By Podiatrists On average a podiatrist writes 24 prescriptions/month for an oral antibiotic. There are ~13 000 practicing podiatrists in the US. 13 000 (24/month) =...

PM716 Pharmacology I Chapter 46 Sulfonamides RMRocco, PhD 1  Oral Antibiotic Use By Podiatrists On average a podiatrist writes 24 prescriptions/month for an oral antibiotic. There are ~13 000 practicing podiatrists in the US. 13 000 (24/month) = 312 000 prescriptions/month for oral antibiotics. W. S. Joseph, J. Lefrock Clinics in Podiatric Medicine and Surgery 13(4):683-699 (1996). 2 Christian Gram (1853-1938) Ueber die isolirte Färbung der Schizomyceten in Schnitt-und Trockenpräparaten. Fortschritte der Medicin 2:185-189 (1884) (The differential staining of Schizomycetes in tissue section and in dried preparations.) 3 Mixed Gram Pos and Gram Neg 4  Gram Stain Procedure 1. Stain dried fixed smear with crystal violet. 2. Add Lugol’s iodine as mordant 3. Wash with alcohol-acetone to decolorize out the blue stain (Gram Neg bacteria loose the blue dye, Gram Pos retain blue dye). 4. Counterstain the Gram Neg bacteria with safranin or basic fuchsin (red dye). 5  Bacterial Cell Walls Gram Pos Gram Neg Peptidoglycan Plasma Membrane Peptidoglycan Plasma Membrane Plasma Membrane 6  Gram Pos Gram Neg Porin Polysacch. Teichoic Lipoteichoic o-antigen Peptidg Plasma Membrane Gram Positive Gram Negative 7  Gram Stain Gram Pos Gram Neg Complex cell wall Simple cell wall 1 layer thick (PTDG) 40 layer thick Porins outer (PTDG) membrane allow Highly polar, hydrophilic drugs in LPS prevent many positive charged antbiotics from getting drugs easily in penetrate cell, Gram Neg streptomycin Pseudomonas aeruginosa resistant to most antibiotics because of the LPS 8  Terms 1 Bactericidal: Kills bacteria in absence of host defense mechanisms. Bacteriostatic: Does not kill, requires host defense to kill the bacteria. Nosocomial: noso komos, one who tends to the sick. 9 # viable Effects on Bacteria bacteria No Drug 106 Bacteriostatic 102 Bactericidal Time 10  Terms 2 Antibiotic: chemical produced by one organism to kill or inhibit another organism. For example, penicillin. Antimicrobial: a chemcial (usually) produced in a test tube used to kill or inhibit an organism. For example, sulfonamide drugs. 11  Terms 3 Nosocomial: hospital acquired. (Gr. nosokomos, one who tends to the sick) Spectrum: range of bacteria that a drug is effective against. Narrow, Broad, Extended. Extended Spectrum: A narrow spectrum drug changed to increase its range. 12  stationary phase log phase Log Number cell death Bacteria lag phase Time Hours 13 Examples of Gram Negative Bacteria Cocci Neisseria Pasteurella Acinetobacter Rods Pseudomonas Bacteroides Escherichia Salmonella Shigella Proteus 14 Examples of Gram Positive Bacteria Cocci Clusters Staphylococcus Pairs/Chains Enterococcus Streptococcus Rods Clostridium Actinomyces Bacilllus 15  Antibiotics: Seven Key Points 1. Drug Class and stem if there is one 2. Spectrum of Activity 3. Mechanism of Action 4. Mechanism(s) of Resistance 5. Combinations to Prevent Resistance 6. Pharmacokinetics 7. Major ADRs 16 Gerhard Domagk (1895- 1964) 17  Gerhard Domagk 1932 Injects Prontosil into mice with streptococcal (Gram positive) infections. All treated mice survive. Domagk treats his own daughter with drug for streptococcal infection. Deutsche Medizinische Wochenschrift 61:250-253 (1935) February 15th He worked for I. G. Farbenindustrie (Bayer Pharmaceutical). 18 Prontosil ™ 19 Gerhard Domagk Awarded Nobel Prize in 1939 Arrested by Nazis, held for 11 days then declines the Prize. Prize held until 1947 then awarded. 20  Prontosil™ Inactive in vitro, only active in vivo. Turns patient’s skin red (a red azo dye) 21  Prontosil™ Prontosil biotransformed in the liver to sulfonamide. Sulfonamide is active in vitro and in vivo. Prontosil is a prodrug converted in vivo to sulfonamide. 22  Sulfonamide The para-NH2 is essential for antibiotic activity. Most sulfa drugs made from substitutions in the sulfur portion of the molecule. Active against Streptococcus, Haemophilus, Actinomyces, Chlamydia, Escherichia 23 Sulfa Drugs in WWII Used to treat all forms of infections. Powder added to open wounds. Drug was also available for im, iv and po administration. 24  Mechanism of Action Bacteria have unique synthetic pathway used to produce folic acid required for DNA synthesis. Synthesis starts with p-amino benzoic acid (PABA). 25  Mechanism of Action In bacteria (not mammals) folic acid is synthesized from PABA Sulfa substitutes for PABA and blocks folic acid synthesis. Folic acid loss results in impaired DNA synthesis. Bacteriostatic. 26  Bacterial Synthesis of Folic Acid Pteridine + Sulfa Competes Dihydropteroic Acid Dihydrofolic Acid Tetrahydrofolic Acid 27  Sulfonamide PABA SULFA PABA SULFA 28 Chapter 46 Sulfonamides, Trimethoprim, & Quinolones 29 © The McGraw-Hill Companies, Inc, Chapter 46 Sulfonamides, Trimethoprim, & Quinolones 30 © The McGraw-Hill Companies, Inc,  Pharmacokinetics F = 70 -100 % following po dose Peak Cp levels in 2 - 6 h post po dose Drug distributes into most tissues including brain and CSF. Major biotransformation is through acetylation. Most metabolites are inactive. 31 Minimum Inhibitory Concentration (MIC) Measurement of the concentration of antibiotic necessary to inhibit growth of a standardized inoculum. Test for resistance. Adjust dose up or down. Find less toxic/costly antibiotic, use drug with lowest MIC and largest ring. 32 Disc Diffusion MIC Assay Bacterial growth XXXXXXXXXXX MIC 1.0 ug/mL 33 Disc Diffusion MIC Assay Bacterial growth XXXXXXXXXXXXXXXXXXXXXXXX MIC Resistant 34 Disc Diffusion MIC Assay Bacterial growth XXX MIC 0.01 ug/mL 35 MIC 36  Minimum Bactericidal Concentration (MBC) MIC = 4 ug/mL 8 7 6 5 4 3 2 1 ug/mL MBC = 6 ug/mL 37 38 39  Cp Max Area Under the Curve (AUC) Cp MIC Time 40  Drug Dosing Drug A t1/2 = 1 h Drug B t1/2 = 8 h Dose q 3 hrs Dose q 24 hrs Cp Cp MIC MIC time h 24h time h 24 h 41  Sulfa Drugs Required sulfadiazine sulfisoxazole silver sulfadiazine trimethoprim + sulfamethoxazole pyrimethamine + sulfadoxine 42  Trimethoprim Specific inhibitor of bacterial dihydrofolate reductase Combined with sulfamethoxazole TMP:SMZ ratio 1:20 in blood to provide improved efficacy. TMP is 20x more active against most bacteria compared to SMZ. Target for TMP is second enzyme in folic acid pathway. 43  Bacterial Synthesis of Folic Acid Pteridine + Sulfa dihydropteroate Competes synthetase Dihydropteroic Acid Trimethoprim Dihydrofolic Acid dihyrofolate reductase Tetrahydrofolic Acid 44  TMP:SMZ Combination (1) Bacteria synthesize Folic acid, it’s vitamin in humans. Humans do not have enzyme target of SMZ. (2) Bacteria can not absorb Folic acid from patient tissue fluids (EXCEPT Enterococci). (3) TMP target, dihydrofolate reductase is found in humans but TMP has 10 000 greater affinity for bacterial enzyme compared to human enzyme. 45  Trimethoprim/Sulfamethoxazole (Bactrim©, Septra©) Also called cotrimoxazole. Mostly used for urinary tract infections but high distribution into tissues after po dosing makes it useful for lower extremity infections. Bacteriostatic against all organisms tested. Good for staph and MRSA Used to treat Pneumocystis pneumonia in AIDS patients. 46  Trimethoprim/ Sulfamethoxazole Allergic reactions possible from mild rash to Stevens-Johnson Syndrome (systemic skin disease) Hemolytic anemia in patients with G6PD deficiency Crystalluria less common than with other sulfa drugs. 47  Trimethoprim/ Sulfamethoxazole DOSE: one tablet per day (160 mg trimethoprim + 800 mg sulfamethaxazole) up to twice per day. 48 Classification of Sulfa Drugs 1. Rapid absorption and excretion: sulfisoxazole, sulfadiazine (Oral absorbable) 2. Poorly absorbed, good for bowel treatment. sulfasalazine. (Oral non-absorbable) 3. Topical use. sulfacetamide, sulfadiazine. 4. Long acting, absorbed rapidly and excreted slowly. sulfadoxine 49  Sulfonamides A 24-year-old sexually active female presents with burning pain during urination, increased urinary frequency and urgency. She reports blood appearance in her urine. Possible diagnosis: urinary tract infection (UTI); uncomplicated cystitis Most common cause E. coli or Staph 50  Sulfonamides Urinalysis revealed bacteriuria: pyuria (pus and WBC in the urine) of 10+ WBC/high-power field in unspun midstream urine. Leukocyte esterase dipstick was positive (when 10+ WBC/high-power field. Urine culture of midstream sample grew E. coli. Typical counts in urine in infection are 102 - 105 bacteria/mL (100 to 100000/mL) 51  Sulfonamides Treatment may include a beta lactam or a sulfa drug. Sulfa drug of choice for UTI is trimethoprim-sulfamethoxazole (TMP/SMX) (Bactrim® or Septra®) po for 3 or more days Trimethoprim is combined with sulfamethoxazole because both have same half-life. 52  Toxic Reactions Crystal formation (precipitation) in urinary tract. Drink large amounts of water, keep urine alkaline. sulfisoxazole. Hemolytic anemia found in G6PD deficiency. Sulfadiazine incidence is 0.05%. Agranulocytosis following sulfadiazine, 0.1%. Aplastic anemia (suppression of bone marrow) rare. 53  Toxic Reactions Hypersensitivity dermatitis (rashes), fever, pruritus. sulfisoxazole incidence 2%. Also, rare incidence of Stevens- Johnson Syndrome. 54  Drugs of Choice for A. Urinary tract infections, sulfisoxazole B. Nocardiosis (Norcardia, soil bacterium) pneumonia, 6 months po sulfasoxazole. C. Toxoplasmosis, pyrimethamine + sulfadiazine combination. Broad Spectrum: Both Gram Pos/Neg including E. coli, Klebsiella, Salmonella, Enterobacter. 55  General Mechanisms of Resistance Methods vary by organism Gene mutation at the chromosome level Plasmid gene mutation(extra chromosomal genes) [source of multi-drug resistance] 56  Mechanisms of Drug Resistance Through Random Mutations 1. Lower the binding affinity of the dihydropteroate synthase for sulfa drug 2. Develop an active transport in the cell wall to remove sulfa drug 3. Develop an alternate pathway for synthesis of folic acid 4. Increase the synthesis of PABA to overcome block by Sulfa. Resistant Staph produce 70x more PABA compared to non-resistant Staph 57  Sulfonamides Sulfa Drugs, 1935, world’s first synthetic antimicrobial. Derived from industrial red dye Prontosil™ Common mechanism of action: inhibit folic acid synthesis. Led to discovery of furosemide (Lasix®), early diuretic Led to discovery of tolbutamide (Orinase®), first antidiabetic 58 59 60 Quinolone Drugs Discovered by George Y. Lesher in 1962 and first introduced into clinical practice in 1969. Drug actions mediated through inhibition of microbial enzymes required for replication. 61  Fluoroquinolones Drugs Targets are two essential bacterial enzymes required for DNA replication. Inhibition of these enzymes causes chromosome to remain unwound and too large to be inserted into progeny cells. Mammalian enzymes not susceptible to inhibition at concentrations used in clinical practice. Topoisomerase II (DNA gyrase) in Gram Negatives Topoisomerase IV in Gram Positives 62 Chapter 46 Sulfonamides, Trimethoprim, & Quinolones 63 © The McGraw-Hill Companies, Inc,  Topoisomerase Enzymes Main function of these enzymes is to uncoil DNA supercoils. Supercoils required in order to pack long DNA strands into limited space within the human nucleus (20-50 micron cells) and the limited space of the cytoplasm of bacteria (1-2 microns). 64  Topoisomerase Enzymes Topoisomerase II (DNA gyrase) causes the relaxation of positively charged supercoiled DNA Toposiomerase IV separates the replicated chromosomal DNA into their respective daughter cells. 65  Topoisomerase Enzymes Bacteria Topoisomerase II (DNA gyrase) Topoisomerase IV Human Topoisomerase II Topoisomerase I 66  Toposiomerase Enzymes In bacteria the fluoroquinoline drugs inhibit the topoisomerase enzymes and prevent DNA replication. Drug examples: ciprofloxacin (Cipro®) levofloxacin (Levaquin®) moxifloxacin (Avelox® ) The Product Insert for ciprofloxacin is on Canvas and is required. 67  Fluoroquinolone Drugs Required norfloxacin moxifloxacin gemifloxacin lomefloxacin ciprofloxacin ofloxacin levofloxacin 68 Quinolone Antimicrobials Nalidixic Acid (NegGram®), 1963, first of the quinolone antimicribials. DNA Gyrase Inhibitor Used for urinary tract infections Excreted too rapidly for systemic use. The drug never builds up in the tissues and plasma to levels required for efficacy against bacteria. Resistance limits drugs use. MIC 4-16 ug/mL (considered very high MIC impossible to achieve in serum). 69  Rationale Drug Design Moxifloxacin (Vigamox®) Controls gyrase inhibition Adds Gram Pos Activity Required for Controls spectrum of gyrase inhibition potency Controls Pharmacokinetics Adds anaerobe activity Drug used as topical ophthalmic for Gram Pos bacteria. 70 Fluoroquinolones Ciprofloxacin (Cipro®) Fluorinated 4- quinolone analogue of nalidixic acid. Bacteriocidal to many gram neg urinary tract infections. 71  Mechanism of Actions Inhibit bacterial DNA Gyrase enzyme in Gram Neg bacteria (E. coli) Supercoiled DNA is relaxed by gyrase. DNA Gyrase prevents over coiling. 72  Mechanisms of Action Topoisomerase IV inhibited in Gram Pos bacteria (S. aureus). Enzyme separates daughter DNA molecules. 73  Pharmacokinetics Well absorbed after po dosing (F = 80 - 90%) Long half life (up to 10 h t1/2) makes once daily dosing possible. Primary route of excretion is renal. Dose adjustment required for CC at 50 mL/min or below. 74  Flouroquinolones Broad spectrum against Gram Neg including chlamydia and mycobacteria Wonder drugs of the 1990’s intended for one stop shopping against all types Gram Neg bacteria. Many of them withdrawn due to liver, renal and cardiac toxicity. Resistance soon reported against S. aureus and P. aeruginosa because of severe over use. 75  Ciprofloxacin (Cipro ) © The most prescribed quinolone. Covers almost all Gram Neg pathogens But staphylococcal infections with up to 90% MSA show resistance. Generally well tolerated. Some nausea and headaches. Drug increases theophylline levels and Cp levels of theophylline should be checked when on Ciprofloxacin (a type of adverse drug-drug interaction, much more on this latter). 76  Ciprofloxacin Tendon pain complaints from patients should be heeded because of rare reports of tendon (Achille’s) reputure. Mechanism unknown. DOSE; 500 - 750 mg po twice a day. Adjust for renal insufficiency. 77  Adverse Effects Well tolerated, with low incidence of nausea, vomiting, diarrhea. Not recommended for patients under age 18 y due to effects on growing cartilage (arthropathy). Convulsions can occur because drug inhibits GABA binding to GABA receptors (another adverse drug- drug interaction). 78  Ciprofloxacin The most prescribed quinolone antimicrobial. Excellent coverage against all Gram Neg bacteria. Poor coverage of the staphylococcal infections. Major ADR include tendon ruptures (Achilles) may be related to connective tissue toxicity which is widely reported. Tendon pain complaints from patients on ciprofloxacin must be followed up. 79  Sulfonamide Drugs General-Purpose Sulfonamides (1) sulfadiazine (2) sulfisoxazole Special Application Sulfonamides (3) mafenide (topical for burns) (4) silver sulfadiazine (topical for burns) (5) sulfacetamide (ophthalmic) (6) trimethoprim-sulfamethoxazole (7) pyrimethamine-sulfadoxine 80  Fluroquinolone Drugs (1) ciprofloxacin anthrax (2) gemifloxacin respiratory (3) levofloxacin respiratory (4) lomefloxacin (5) moxifloxacin (6) norfloxacin (7) ofloxacin 81  Case Study 59-year old female patient, febrile (38.5oC, 101.3oF) with history of frequent painful urination. Urine is positive for leukocyte esterase. She has had three similar episodes in the past year and is taking daily calcium for osteoporosis. She has been treated multiple times in the past year with trimethoprim- sulfamethoxazole (Septra®) 82  Case Study Try a fluoroquinolone (ciprofloxacin etc). Resistance may have developed to the sulfa combo. Pick one that achieves good urinary levels. Take 2 h before or 4 h after calcium supplement (avoid an adverse drug- drug interaction). Calcium blocks absorption of fluoroquinolone antibiotics. 83  Antimicrobials (1) Antifolate Drugs Sulfonamides (“sulf” in their name). Trimethoprim/sulfamethoxazole combination Pyrimethamine/sulfadoxine (2) Quinolones (DNA Gyrase Inhibitors) 7 drugs all end in “oxacin” ciprofloxacin etc. 84