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3 mehanisms that may lead to Peptic Ulcer disease
- Ethology- Infections (H. Pulori)
- Hyperproduction of HCL- function of the parietal calls of the stomach
- Inadequate mucosal defense against HCL
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Infectious
- Antimicrobial agents (based on efficiency cure (erradication rate)
- Current reginen of choice (90% erradication rate)
- -2 week combo course with:
- Bismuth
- Metronidazole
- Tetracycline
- Anti-secretory drug (usually added)
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Second line regiments (erradication rate 80-90%)
- Combo of 2 antimicrobial agents:
- Metronidazole
- Amoxicillin or Clarithromycin
- Antisecretory drug
If you use 1 antimicrobial agent - have a 20-40% erradication rate
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What is the reccurrance rate of patients treated only with antisecretory agents?
60-100%
For those receiving recommended regimen- rate is less then 15%
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HCL production
HCL secretion (parietal cells) is controlled by:
- Actylcholine (increase intracellular Ca++ ion)
- Histamine (activation of adenyl cyclase)
- Prostaglandine E2 and I2 (lower HCL production)
- Gastrin (increase intracellular Ca++ ion)
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The agents blocking the secondary messangers acting protein pump
- Dicylomine blocks the cholinergic receptor
- Cimetidine blocks the H2 histimine receptor
- Misoprostol stimulates the prostaglandin receptor
- Omeprazole blocks the proton pump
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H2 receptor antagonists Chief clinical use
Inhibitor of gastric acid secretion by reducing intracellular concentration of cyclic AMP.
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H2 receptor antagonists Actions
Fully reversible competitive antagonist of histamine receptors completely inhibiting gastric acid secretion, partial inhibition of gastric acid secretion induced by acetylcholine and bethanechol.
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H2 receptors antagonists Therapeutic use
All agents are equally effective to promote gastric and duodenal ulcer healing. There may be a recurrance rate of 60-100% per year if H pylori superinfection is present
- Zollinger-Ellison syndrome (gastrin producing tumor)
- Acute stress ulcers
- Gastroesophageal reflux
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H2 receptor antagonist agents
- Climetidine (tagamet)
- Ranitidine (zantac)
- Famotidine (pepcid)
- nizatine (axid)
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Cimetdine (tagamet)
- Metabolized in the kidney- good to use if cant use a drug that is metabolized in the liver
- 30% of dose is metabolized by microsomal enzymes thus 70% excreted unchanged in urine.
- Due to its anti-androgenic and Prolactin stimulation, effect may induce gynecomastia, galactorreha, and decreased sperm count.
- Is a P-450 enzyme inhibitor slowing metabolism of drugs that utlizes the system increasing their serum concentrations.
- -Warfarin, Diazepam, Phenytoin,Quinidine, Carbamazepine, Teophylline, and Imipramine
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Ranitidine (Zantac)
Longer acting and more potent than Cimetidine
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Famotidine (Pepcid)
Similar to Ranitidine but more potent
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Nizatidine (Axid)
Similar to Ranitidine but principally metabolized in the kidney and bioavailability is near 100%
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Prostaglandins
Inhibits HCL secretion and stimulates mucus and bicarbonate production
-Misoprostol (cytotec)
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Misoprostol (cytotec)
- Clinically effective at higher doese and its routine use may be only justified in those patients- Using NAIDS
- Since it produces uterine contraction it is contraindicated during pregnancy.
- Diarrhea and nausea are the most common adverse effects
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Inhibitors of proton pump
Supress secretion of H ion into gastric lumen
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Actions of inhibitors of proton pump
Inhibits basal and stimulated gastric acid secretion. More then 90% of supression begins 1-2 hours after dose.
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Therapeutic use of proton pump inhibitors
- Short term treatment of erosive esophagitis and duodenal ulcer.
- Long term treatment of Zollinger- Ellison Syndrome.
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Agents of Proton pump inhibitors
- Omeprazole (prilosec)
- Lansoprazole (prevacid)
- esomeprazole (nexium)
- pantoprazole (protonix)
- Rabeprazole (Aciphex)
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Adverse effects of proton pump inhibitors
- Increased incidence of gastric Carcinoid tumor
- prolonged hypochlorhydria
- secondary hypergastrinemia
- increased concentration of viable bacteria
- Omeprazole interferes with oxidaton of Warfarine, Phenytoin, Diazepam, and Cyclosporine
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Antacids
- Weak bases which react with gastric acid and water to form a salt diminsihing gastric acidity,
- Many products varying in chemical composition, neutralizing capacity and sodium content.
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Agents of Antacids
Aluminum or magnesium salts
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Adverse effects of Antacids
- Constipation (aluminum) (maalox and mylanta)
- diarrhea (magnesium) (gaviscon, mylanta)
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Mucosal protective agents
- Sucralfate (carafate)
- Colloidal bismuth
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Sucralfate (carafate)
Complex of aluminum hydroxide and sulfated sucrose which forms a complex gel with mucus impairing diffusion of HCL.
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Colloidal bismuth
- Inhibits pepsin
- Increase mucus secretion
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Vomiting reflex center
- Chemoreceptor trigger zone (caudal end of 4th ventricle) Responds to chemical stimuli in blood of CSF
- Vomiting center (lateral reticular formation of medulla)- Coordinated the mechanical (motor) mechanism of vomit
Although nausea and vomits are not exclusive of chemotherapy, 70-80% of patients will experience this symptom. 10-40% experience the symptoms before therapy due to anticipation.
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Emetic actions
Agents or their metabolites may activate the center by the releasing and the actons of several neuroreceptors (Dopamine and Serotonine)
Idiosyncratic response (smell, color, etc)
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Emetric Potential of chemotherapeutic drugs
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Strong emetric potential
(some used for leukemia)
- Cisplastin
- Mechlorethamine
- Streptozocin
- Decarbazine
- Carmustine
- Dactinomycin
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Moderate Emetric Potential
- Cyclosphosphamide
- Doxorubucin
- Carboplastin
- Mitomycin
- Asparaginase
- Azacytidine
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Mild Emetric Potential
- Fluorouracil
- Methortrexate
- Etoposide
- Vincristine
- Bleomycin
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Drugs used to control chemotheraphy induced emesis
- Phenotyazines
- Substituted benzamines
- Butyrophenones
- Benzodiazepines
- Corticosteroids
- Canabinoids
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Phenotyazines (Prochlorperazine)
Block dopamine receptors. Effective against low or moderate ematogenic agents (fluorourcil, doxorubicin)
Side effects- Sedation, hypotension and extrapyramidal symptoms
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Substituted benzamines (Metoclopramide)
Effictive at high dose against highly ematogenic agents (eg Cisplastin)
Side effects- Sedation, diarrhea, and extrapyramidal symptoms limit high doses
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Butrophenones (haloperidol)
Moderatly effective antiemetic
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Benzodiazepines (lorazepam, alprazolam)
Requires a perscription- pt can get dependent
- Low potency antiemetic agents
- Beneficial properties include: Sedative anxiolitic and amnesic, useful in anticipatry vomits
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Corticosteroids (dexamethasone, methylprednisolone)
Useful against mild to moderate emetogenic drug. May be involved in prostaglandin blockage.
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Canabinoids (mary jane) (dronabinol, nabilone)
- Mariuana derivatives
- Seldom used due to side effects: Dysporia, hallucination, sedation, vertigo, and disorientation.
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Serotonine Antagonists
Ondansetron (Zorfan)
Granisteon (Kytril)
Block pripheral and central receptors. May be administered as a single does PO or IV and effective against all grades.
- Ondansetron is also effective as post operative nausea and vomits
- Headache is most common side effect
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Antiemetric Activity- High drugs
- Serotonin antagonists
- Substituted benzamide
- Phenothiazine
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Antiemetric activity- Moderate
- Butyrophenone
- Corticosteriod
- Cannabinoid
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Antimetic activity- Low
- Antihistimine
- Anticholinergic
- Benzodiazepine
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Percent response fron drug combos
- Dexamethasone, Ondansetron = 91%
- Dexamethasone, Diphenhydramine, Metoclopramide, Droperidol = 76%
- Lorazepam, Dexamethasone, Metoclopramide = 63%
- Diphenhydramine, Dexamethasone, Metoclopramide = 58%
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Antidiarrheals
- Diphenoxylate
- Loperamide
- Kaolin
- Pectin
- Methylcellulose
- Activated attapuigite
- Aspirin
- Indomethacin
- Bismuth subsaticylate
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Antidiarrheals
Decreased motility (diphenoxylate, loperamide) (meperidine analogs) with Opiod like action= inhibits acetylcholine release, and decreases peristalsis
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Side effects of Antidiarrheals
- Drowsiness, dizziness, and abdominal pain
- May cause Toxic megacolon contraindicated in children and patients with colitis.
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Adsorbents (kaolin, pectin, methycellulose, and activated attapulgite
Action
- adsorption of toxins, or coating mucosa (protective)
- -May interfere with absorption of other drugs
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Agents that modify fluid or electrolyte transport
- NSAIDS (indometacine, asperine) by inhibiting prostaglandin synthesis.
- Pepto Bismol (bismith subsalicilate (choice for traveler's diarrhea)
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Laxatives
Castor oil, Senna, Aloe, Phenolphthalein, Bisacodyl, Hydrophilic colloids, Methylcellulose, Psyllium seeds, Bran, Magnesium hydroxide, Polyethylene glycol, Lactulose, Docusate sodium, Mineral oil, Glycerine suppositories
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Laxatives
- Increase movement of food along GI
- Irritants- Castor oil brake down to rinolinoleic acid which is very irritant and increases peristalsis.
- Bulking agents (most effective)- Methylcellulose, psyllum seeds
Stool softeners- Mineral oil and Glycerine suppositories
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Antimicrobial agents
Drugs that are effective against microorganisms through "selective" toxicity without affecting the host cells.
Appropriate agent
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FDA Catagory Antimicrobial fetal risk
- A- No risk
- B- only studies on animals, suggest potential toxicity
- C- Animal fetal toxicity demonstrated; human risk undefined
- D- Human fetal risk present, but benefits outweigh risks
- X- Fetal risk present, does not outweigh benefits; contraindicated in pregnancy.
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B category drugs
- B- Lactams
- B- Lactams with inhibitors
- Cephalosporines
- Aztreonam
- Clindomyclin
- Erythromycin
- Azithromycin
- Metronidazole
- Nitrofurantoin
- Sulfonamides
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C Catagory drugs
- Chloramphenicol
- Fluoroquinolones
- Clarithromycin
- Trimethoprim
- Vancomycon
- Gentamicin
- Trimethoprim-sulfamethoxozole
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D Category drugs
- Tetracyclines
- Aminoglycosides (except gentamicin)
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Detecting the microbial agents
- Direct microscopic visualation
- Cultivation and Identification
- Detection of microbial antigens
- Detection of microbial RNA or DNA
- Detection of host immune response
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Ideally
Begin therapy after identification and sensitivity
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In reality
Therapy is begun before ID and sensitivity determined
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Why would you begin therapy before the identification and sensitivity is determined
May be detrimental to life
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Emperic therapy
- Broad cover against bacterial infection
- Effective against gram + and - anaerobes.
- Combo of antibiotics or single broad spectrum
You will get culure results and sensitivity depending on if it is gram + or -, or mixed flora
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Agent selection is by:
- Patient history
- Immune Status
- Community vs Hospital acquired (nosocomial)
- Site of infection
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Site of infection
- Antibiotic has to reach the area
- Difficult sites to reach sanctuaries
- -Abcess
- -BBB
- -Prostate gland
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Host status
- Immune status
- Renal function (aminoglucosides)
- Hepatic function (erythromycin)
- Pregnancy (all agents cross the placenta)
- Lactation
- Age (all functions diminish with age)
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Bacterial factors
Identity, Susceptibility
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Host Factors
- Site of Infection
- Allergies
- Renal function
- Hepatic function
- Neutropenia- lack of adequate number of neutrophils
- GI function
- Underlying diseases
- Concomitant drugs
- Pregnancy
- Desired route of administration
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Drug Factors
- Activity against pathogen
- Ability to arrive in site of infection
- Potential drug interactions
- Dosing frequency
- Taste
- Stability at different temperatures
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Cost of therapy
- Often, several drugs have similar effectiveness but different costs.
- ex Clarithromycin costs $120, and Tetracycline is $5
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Drug function- 2 ways
- Bacteriostatic
- Bactericidal
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Bacteriostatic
- Drugs that arrest growth and replication of bacteria limiting spread of infection while immune system works.
- These agents DONT kill the microorganism
- ex- Chloramphenicol
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Bactericidal
- Agents that eliminates (KILL) microorganism
- ex- Penicillin
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ID sensitivity of organism
- Take a culture in the media
- MIC- Minimum inhibitory conc= lowest conc of an antibiotic that inhibits bacterial growth.
- MBC- Minimum bactericidal concentration= The lowest conc of antiboitic that kills 99.9% of bacteria.
LOOK AND UNDERSTAND GRAPHS ON SLIDES 15,16,17
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Spectrum of therapy
- Particular actibity of the drug
- Narrow
- Extended
- Broad
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Narrow
Single or limited group of organism (Isoniacid)
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Extended
- Effective against gram + and gram - organism
- Ampicillin
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Broad
- Wide variety of microbial species
- Teyracycline, Chloramphenicol
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Drug combination
It is wise to use only one agent with higher specificity for the organism decreasing superinfection and emergence of resistant organism
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Drug combo advantages
Synergism (combo is more efficient than either used separately (B- lactams and Aminoglycosides)
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Disadvantages to drug combos
Some agents work only while organism is growing. If combined with bacteriostatic agent it becomes ineffective.
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Drug resistance
- Bacterias are resistant when the agent fails to halt its growth by the maximal level of antibiotic tolerated by the host
- Genetic alteration- Spontaneous mutation, Transfer of drug resisance by R factors (plasmids)
- Modification of target site (eg Staph aureus)
- Decrease accumulation (Decreased permeability for agent)
- Enzymic inactivation (B- lactamase resistant organism)
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Complications of therapy
- Hypersensitivity
- Direct toxicity
- Superinfections
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Hypersensitivity
Reaction to drig or metabolites is frequent (eg Penicillin)
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Direct toxicity
High levels in serum may be toxic to the host (Aminoglycoside produce ototoxicity)
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Superinfections
Therapy may alter the normal flora allowing overgrowth of opportunistic organisms
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Prophylactic antibiotics
- Situations in which antibiotics are used for prevention.
- Restricted to situations where its use outweighs its potential risk.
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examples on when to use prophylactic antibiotics
- 1- Prevention of strep infections in pts with a history of rheumatic heart disease. Pts may require years of treatment.
- 2- Pretreatment of patients undegoing dental extractions who have implanted prosthetic devides, such as artificial heart valves, to prevent seeding of the prosthesis.
- 3- Prevention of tuberculosis or menigitis among individuals who are in close contact with infection pts.
- 4- Treatment prior to certain procedures to prevent infection.
- 5 Treatment of the mother with zidovudine to protect the fetus in the cause of HIV infected, pregnant women.
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Classifications of antimicrobial agents
- Inhibitors of metabolism (Sulfonamides, Trimethoprim)
- Inhibitors of cell wall synthesis (B-Lactams, Vancomycin)
- Inhibitors of protein sysnthesis ( Tetracyclines, Aminoglycosides, Macrolides, Clindamycin, Chloramphenicol)
- Inhibitors of nucleic acid function or synthesis (Fluroroquinolones, Rifampin)
- Inhibitors of cell membrane function (Isoniazid, Amphotericin B)
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Cell wall inhibitors
- These agents are active against proliferating microorganisms
- The most important members are the B-lactam antibiotics since the ring is esential for antimicrobial activity.
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Cell wall inhibitors
- B lactam antibiotics:
- Penicillins
- Cephalosporines
- Carbapenems
- Monobactams
- Other antibiotics:
- Vancomycin
- Bacitracin
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Penicillins
Interfere with transpeptidation or cross-linkage, last stage of cell wall synthesis.
- Rationale: Makes bacterial wall less stable and osmotically fragile, therefore bactericidal in nature
- Ineffective against organisms that don't synthesize peptidoglycans as: mycobacteria, protozoa, fungi, viruses.
- Penicillins bound to preiplasmic "receptors" where bacterial enzymes work to produce and modify its wall.
- Many bacteria produce autolysins for remodeling the wall.
- In presence of Penicillins they "synergistically" destroy its wall.
Obtained from the mold. Penicillum chrysogenum
- Differ from the substrate R group:
- Natural Penicillins: Antistaphylococcal
- Semi-synthetic: Extended spectrum, Antipseudomonal.
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Standard Penicillins
- Crystalline penicillin G (IV)
- Penicillin V (po)
- Aqueus procaine penicillin G (IM)
- Benzathine penicillin G (IM)
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Antistaphylococcal Penicillins (COMND)
- Methicillin (IV)
- Nafcillin (IV)
- Isoxazloyl penicillins (IV)
- Oxacillin (IV)
- Cloxacillin (PO)
- Dicloxacillin (PO)
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Aminopenicillins
- Ampicillin (IV or PO)
- Amoxicillin (IV or PO)
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Antipseudomonal penicillins
- Carboxygenicillins
- Carbenicillin (IV)
- Ticarcillin (IV)
- Ureidopenicillins
- Piperacillin (IV)
- Azlocillin (IV)
- Mexlocillin (IV)
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Natural Penicillins
Pen G. (benzylpenicillin)
- used IV or IM- effective against Gram + and - organisms but is susceptible to inactibation by B-lactamase penicillinases.
- Not resistant to acid (not used orally)
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Therapeutic applications for Penicillin G
- Streptococcus sp. (pneumoniae, pyogens, viridans)
- Neisseria sp (gonorrhea, meningitides)
- Clostridium perfringes
- Bacilus antracis
- Corynebacterium diphteriae
- Treponema pallidum
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Pen V.
Similar spectrum to Pen G. but more acid stable (used in oral indections by anaerobes)
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Antistaphylococcal
Penicillinase resistant agents use restricted for resistant organisms (COMND)
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Semi-Synthetic penicillins
- extended spectrum
- ampicillin
- amoxicillin
- Spectrum similar to Pen G.- but more effective against Gram (-)
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Resistance
Can be natural or acquired
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Natural Resistance
Organism lacking peptidoglycan cell wall
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Acquired Resistance
- Plasmid transfer (significant problem)
- B-lactamase activity (constitutive vs. acquired)
- decreased permeability to drug
- altered penicilin binding proteins
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Pharmacokinetics
- Route determned by stability to gastric acid and severity of infection
- PO- oral
- Depot (IM) Procaine, Pen G, and Benzyl Pen G)
- IV (antipseudomonal)
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Absorption
Most are incompletly absorbed after oral intake (except amoxicillin)
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Distribution of Penicillin
Free drug is distributed well including the placenta but the hemato-encephalic barrier is limited to acute stages of disease
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Matabolism of Penicillin
Usually insignificant
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Excretion of Penicillin
Primary route is renal tubular secretion and glomerular filtration
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Adverse reactions of Penicillin
- Hypersensitivity (most important) 5% of patients (penicilloic acis reacts with proteins (hapten))
- Diarrhea
- Nephritis (eg. Methicillin)
- Neurotoxicity (may produce seizures if injected intrathecally)
- Platelet dysfunction (antipseudomonal)
- Caution toxicity- usually administered as Na+ or K+ salts (avoided by ising the most potent which allow for lower doses)
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