Lecture 7 Chapter 25 Antibacterials: Penicillins & Cephalosporins

Lecture 7 Chapter 25 Antibacterials: Penicillins & Cephalosporins

Antibacterials Antibacterials/antimicrobial drugs - Substances that inhibit the growth of or kill bacteria or other microorganisms (microscopic organisms bacteria, viruses, fungi, protozoa) Bacteriostatic Inhibits growth of bacteria Bactericidal Kills bacteria Peaks & Troughs Serum antibacterial levels for drugs w/ a narrow therapeutic index - Too high drug toxicity (Peak - 1 hr. after drug infused) - Too low therapeutic range (Trough - before dose)

Antibacterials Mechanism of Action: 1. Inhibition of cell wall synthesis - Bactericidal 2. Alteration in membrane permeability - ‘Cidal’ or ‘Static’ 3. Inhibition protein synthesis - ‘Cidal’ or ‘Static’ 4. Inhibition of bacterial RNA & DNA - Inhibits synthesis of RNA & DNA 5. Interferes with metabolism in the cell - ‘Static’

Antibacterials Drugs 1. Penetrate bacterial cell wall in sufficient concentrations 2. Affinity to the binding sites on the bacterial cell: - Time drug remains at binding sites effect - Time controlled by pharmacokinetics

Antibacterials Pharmacodynamics - - Concentration at site or exposure time for drug plays an important role in bacteria eradication - Duration of time for use of antibacterial varies according to type of pathogen, site of infection & condition of host - With some severe infections - continuous infusion more effective than intermittent - Body defense & drugs work together to stop infectious process - Effect drug & host’s defense mechanisms

Effects of concentrated drug dosing

Antibacterials Bacterial Resistance - result naturally or may be acquired * Natural (inherent) w/o previous exposure to antibiotic ie. pseudomonas resistant to Penicillin G * Acquired prior exposure to antibacterial ie. staph aureus was sensitive to PCN G, now it’s not Nosocomial infections - infections acquired while clients are in the hosp. Many are mutant strains resistant to many antibacterials Prolonged hospital stay Antibacterial resistance occurs when antibiotics are used frequently

Antibacterials Culture & Sensitivity - Bld test done to determine effect drugs have on a specific organism Culture organisms responsible Sensitivity what antibiotic will work best Narrow & Broad Spectrum Narrow - primarily effective against 1 type of organism Broad - effective against both gram & gram - organisms * Used before isolating organism through C & S * Not as effective as narrow spectrum against those single organisms

Antibacterials Penicillins (PCN) From mold genus Penicillium - ‘miracle drug’ from WWII A beta-lactum structure (beta-lactum ring) interferes w/ bacterial cell wall synthesis by inhibiting the bacterial enzyme necessary for cell division & synthesis Bacteria die of cell lysis (breakdown) Both ‘static’ & ‘cidal’ in nature Mainly referred to as beta-lactum antibiotics (enzymes produced by bacteria that can inactivate PCN Penicillinases beta-lactamases which attack PCN

Antibacterials Penicillins Natural Penicillins Penicillin G, Penicillin V, Procaine, Bicillin - Good gram , fair gram - , good anaerobic - PCN G more effective IV or IM, but painful d/t aqueous solution - PCN V PO; peak 2 - 4 hrs

Antibacterials Penicillins Aminopenicillins (Broad Spectrum) Amoxicillin (Amoxil), Ampicillin (Omnipen), Bacampicillin HCL (Spectrobid) - Gram & Gram - Costlier - Inactivated by beta-lactamases ineffective against Staphylococcus aureus (staph. A) - Amoxicillin most prescribed PCN derivative for adults & children

Antibacterials Penicillins Penicillinase - Resistant Penicillins Methicillin (Staphcillin), Nafcillin (Unipen), Oxacillin (Bactocil) - Used to treat penicillinase-producing Staph A. - Gram , not effective against Gram - IV & PO

Antibacterials Penicillins Extended - Spectrum Penicillins Carbenicillin (PO), Mezlocillin, Piperacillin, Ticarcillin, Ticarcillin-clavulanate (Timentin) - IM & IV - Broad spectrum - good gram (-), fair gram ( ) - Good against Pseudomonas aeruginosa - Not penicillinase resistant

Antibacterials Penicillins SE & adverse reactions of Penicillins 1. Hypersensitivity - mild or severe Mild rash, pruritus, & hives - Rx w/ antihistamines Severe anaphylactic shock - occurs w/ in 20 min. - Rx w/ epinephrine 2. Superinfection - secondary infection when normal microbial flora of the body disturbed during antibiotic Rx Mouth, resp. tract, GI, GU or skin - usually fungus 3. Organ toxicity - esp. liver & kidneys where drugs metabolized & excreted (aminoglycosides)

Antibacterials Cephalosporins From a fungus Cephalosperium acremonium - Gram ( ) & gram (-) - Resistant to beta - lactamase - Bactericidal - action similar to PCN’s - 4 groups (generations) - each effective against a broader spectrum of bacteria - about 10% of people allergic to PCN also to allergic to cephalosporins - Action - inhibits bacterial cell wall synthesis - IM & IV - onset almost immediate

Antibacterials Cephalosporins 1st Generation Cephalosporins - cefadroxil (Duricef) & cephalexin (Keflex) - PO; Cefazolin (Ancef) & cephalothin (Keflin) - IM - Gram ( ), & gram (-) - Esp. used for skin/skin structure infections - Keflin used for resp, GI, GU, bone, & joint infections

Antibacterials Cephalosporins 2nd Generation Cephalosporins - cefaclor (ceclor) PO, cefoxitin (Mefoxin), cefuroxime (Zinacef), cefotetan (Cefotan) - IM & IV - Gram ( ), slightly boarder gram (-) effect than 1st generation - for harder to treat infections

Antibacterials Cephalosporins 3rd Generation Cephalosporins - cefotaxime (Claforan), ceftazidime (Fortaz), ceftriaxone (Rocephin), cefixime (Suprax) - IM or IV - More effective against gram (-), less effective against gram ( ) - for harder yet to treat infections 4th Generation Cephalosporins - cefepime (Maxipime) - IV or IM - Resistant to most beta-lactamase bacteria - greater gram ( ) coverage than 3rd generation

Ch. 26 - Antibacterials Macrolides, Lincosamides, Vancomycin All differ in structure, but similar spectrums of antibiotic effectiveness to PCN Used as PCN substitutes, esp. w/ people allergic to PCN Erythromycin frequently prescribed if hypersensitive to PCN Macrolides - Erythromycin, Azithromycin (Zithromaz), Clarithromycin (Biaxin) - PO/IV, Dirithromycin (Dynabac) PO - Broad spectrum of activity - Low to mod dose bacteriostatic - high doses bactericidal SE GI disturbances, Allergic rxns Hepatotoxicity

Antibacterials Lincosamides Clindamycin (Cleosin), Lincomycin (Lincorex) - PO, IM, IV - Inhibit bacterial protein synthesis - ‘Static’ & ‘cidal’ actions depending on drug dosage - effective against most gram ( ), no gram (-) - Clindamycin more effective than lincomycin

Antibacterials Vancomycin Glycopeptide bactericidal antibiotic - IV - Use: Drug resistant Staph A., cardiac surgery prophylaxis for clients w/ PCN allergies - SE Ototoxicity - damage to auditory branch of 8th cranial nerve permanent hearing loss or loss of balance & Nephrotoxicity - Serum Vanco levels drawn to minimize toxic effects

Antibacterials Tetracyclines Tetracycline, Doxycycline (Vivbamycin), Minocycline (Minocin) - Broad spectrum - Gram ( ) & gram (-) bacteria - Bacteriostatic - Wide safety margin, but many side effects - Primarily used for skin/skin structure infections - Also used to treat Helicobacter pylori (H. pylori) bacterium in stomach that can cause peptic ulcers - Tetracycline mostly

Antibacterials Tetracyclines Considerations - SE Photosensitivity - sunburn rxn - Should not be given to children 8 yrs or to women in last trimester of pregnancy Irreversibly discolors permanent teeth - Tetracycline during 1st trimester of pregnancy can cause birth defects - Take on an empty stomach - antacids & dairy products prevent absorption of the drug

Antibacterials Aminoglycosides Amikacin (Amikin), Gentamicin (Garamycin), Tobramycin (Nebcin), Netilmicin (Netromycin) - Inhibits bacterial protein synthesis, ‘cidal’ - Gram (-) & some gram ( ) - Used to treat serious infections - Cannot be absorbed from GI tract, cannot cross into CSF - To ensure a desired bld level - IV use - Narrow therapeutic range - Peak & Trough levels drawn - SE Ototoxicity, Nephrotoxicity

Antibacterials Fluoroquinolones (Quinolones) Ciproflaxacin (Cipro), Levofloxacin (Levaquin), Ofloxacin (Floxin), Norfloxacin (Noroxin) - IV or PO - Interferes w/ synthesis of bacterial DNA - Bactericidal - Broad spectrum - gram (-) & gram ( ) - Rx - UTI’s, lower resp. infections, bone & joint infections, GI, skin - Wide safety margin - CI - Children 14 yrs

Chapter 27 Sulfonamides One of the oldest - broad spectrum - gram - & gram First group of drugs used against bacteria Bacteriostatic - inhibits bacterial synthesis of folic acid, essential for bacterial growth Alt. for people allergic to PCN Use - UTI’s, ear infections, newborn eye prophylaxis - Not effective against viruses or fungi PO, sol’n & ointment for ophthalmic use & cream - Silver sulfadiazine (Silvadene) - for burns

Antibacterials Sulfonamides Special consideration - Drink fluids to prevent crystalluria (d/t poor water solubility) & hematuria SE - allergic response - skin rash & itching - Anaphylaxis not common - Bld disorders w/ prolonged use & high doses - GI disturbances - Photosensitivity

Chapter 28 Antitubercular, Antifungal Peptides, & Metronidazole Inhibit or kill organisms that case diseases Tuberculosis (TB) - Caused by the acid-fast Bacillus Mycobacterium tuberculosis - frequently referred to as the tubercle bacillus - One of the major health problems in the world & kills more people than any other infectious disease - About 11/2 billion people have TB & don’t know it - TB in US until 1980’s & AIDS d/t compromised immune system

Antiinfective Agents Tuberculosis Transmitted by droplets dispersed in the air through coughing & sneezing inhaled into alveoli (air sacs) of lungs spread to other organs via blood & lymphatic system - Strong system phagocytes stop multiplication of tubercle bacilli - Compromised system tubercle bacilli spread

Antiinfective Agents Tuberculosis Drugs: Isoniazid (INH) - 1952, Rifampin - Prophylactic therapy for persons close to TB, HIV , a TB skin test, young children in contact w/ active TB, - Family members on Isoniazid 6 months to 1 yr - Spectrum Myobacterium tuberculosis, ‘cidal’ - Combo of Isoniazid & Rifampin No bacterial resistance & less Rx time more effective - SE ‘flu-like’ symptoms, neurotoxicity, hepatotoxicity, Monitor drug therapy carefully

Antiinfective Agents Antifungals (Antimycotics) Topical - skin/mucus membranes (athletes foot) Systemic - lung, CNS (pulmonary conditions, meningitis) Fungi - Candida (yeast) - normal flora of mouth, skin, intestine, vagina Candidiasis opportunistic infection - body’s defense mechanism impaired allowing overgrowth of fungus Drugs - antibiotics, contraceptives & immunosuppressives may alter body’s defense mechanisms - mild vaginal yeast infection, severe systemic infect.

Antiinfective Agents Polyenes Amphotericin B (Fungizone), Mystatin (Mycostatin) Broad spectrum antifungal activity Fungizone IV administration SE Flushing, chills, N & V, dec. BP Considered highly toxic - nephrotoxicity & electrolyte imbalance poss Nystatin orally or topically for candidal infections Swish & swallow to allow contact w/ mucus membranes

Antiinfective Antifungal Metronidazole (Flagyl) - treatment of various disorders associated w/ organisms of GI tract - PO and IV SE GI discomfort, Headache, depression (not common) Also used to treat H. pylori associated w/ peptic ulcers

Math Problems A dose of 200 mcg is ordered. The strength available is 0.3 mg. in 1.5 mL. Convert mg to mcg. 1 mg 1000 mcg 0.3 mg 300mcg 200 mcg X 1.5 ml. X ml 300 mcg 2 X 1.5 3 X 3 To give 200 mcg you must administer 1 ml. 1 ml 3

A dosage of 0.7 g. has been ordered. Available is a strength of 1000 mg. in 1.5 mL. Convert g. to mg. 0.7 g 700 mg 700 mg. X 1000 mg. 7 10 X 1.5 mL X mL 1.5 mL 10.5 10 10.5 divided by 10 1.05 Round up to 1.1. So administer 1.1 mL. X