医学PPT课件抗生素.pptVIP

Problem 3 - Range of Activity R= hydrophobic results in high activity vs. Gram + bacteria and poor activity vs. Gram - bacteria Increasing hydrophobicity has little effect on Gram + activity but lowers Gram - activity Increasing hydrophilic character has little effect on Gram + activity but increases Gram - activity Hydrophilic groups at the a-position (e.g. NH2, OH, CO2H) increase activity vs Gram - bacteria Results of varying R in Pen G Problem 3 - Range of Activity Examples of Aminopenicillins include: Class 1 - NH2 at the a-position Ampicillin and Amoxicillin (Beecham, 1964) Ampicillin (Penbritin) 2nd most used penicillin Amoxicillin (Amoxil) Problem 3 - Range of Activity Active vs Gram + bacteria and Gram - bacteria which do not produce b-lactamases Acid resistant and orally active Non toxic Sensitive to b-lactamases Increased polarity due to extra amino group Poor absorption through the gut wall Disruption of gut flora leading to diarrhea Inactive vs. Pseudomonas aeruginosa Examples of Aminopenicillins Include: Properties Amoxicillin is sometimes used together with clarithromycin (Biaxin) to treat stomach ulcers caused by Helicobacter pylori, a Gram - bacteria Also, a stomach acid reducer (lansoprazole, or Prevacid) is sometimes added. Helicobacter pylori Helicobacter pylori is linked to stomach inflammation, which may also result in gastric ulcers and stomach cancer In the early 20th century, ulcers were believed caused by stress In 1982, Robin Warren and Barry Marshall, two Australian physicians, suggested link between H. pylori and ulcers Medical community was slow to accept (first abstract describing such results was rejected for a poster) In 2005, the two researchers, Barry Marshall and J. Robin Warren, received the Nobel Prize in medicine for their discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease Problem 3 - Range of Activity Prodrugs of Ampicillin (Leo Pharmaceuticals - 1969) Properties Inc