Copyright, Purdue Research Foundation, 1996

| BMS 445 Intro | | Drug Groups | | E-mail | | Slides / Graphics |


Classes of Penicillins

Natural penicillins


Beta-lactamase resistant penicillins (Antistaphylococcal penicillins)

Extended spectrum penicillins (Antipseudomonal penicillins)

Beta-lactamase inhibitors





Adverse Effects

Study Questions

  1. What is the potential importance of clavulanic acid in penicillin therapy?
  2. Is it proper to use penicillin G topically? Why not?
  3. What is the difference in indications and routes for the various salt forms (e.g., sodium, potassium, procaine, benzathine, trihydrate as appropriate for each drug) of penicillin G and ampicillin? Think about maximum achievable plasma concentrations and reasons for needing to vary absorption rates.
  4. You should know the major family groups of the penicillins? What is the relative importance of each? How do the new derivatives, e.g. those in the antipseudomonas group, compare to the classical penicillin G with respect to activity on sensitive gram positive organisms?
  5. What is the importance of noting whether a derivative of a drug is acid resistant? Name two acid resistant penicillins, one each from the natural penicillins and one from the aminopenicillins.
  6. You should know that methicillin is the classical anti-staphylococcal pencillin derivative. Yet staphylococci can become resistant to it. What is the basis of this resistance and what does it predict for the potential effectiveness of other beta-lactam antimicrobials against the resistant organism?
  7. Do penicillins distribute widely throughout the body, i.e. achieve therapeutic concentrations? Into cells?
  8. What is the basis of the use of probenecid to increase the concentration of penicillin (and, presumably certain other beta-lactams) in the CSF? Would you expect probenecid to have the same effect on cephalosporins if biotransformation were not a factor?
  9. What is the major route of excretion of the penicillins? Why was probenecid used in conjunction with penicillin in earlier days? This is an example of the kind of mechanism pharmacologists love to talk about.
  10. What is the only significant adverse reaction to penicillin per se? Why is the specificity (selectivity) of the penicillins so high? Note that penicillins applied directly to the brain can cause seizures, but this is not a typical use.
  11. What effect might the rapid iv injection of massive doses of potassium penicillin have on cardiac function. Note that 200,000 units of penicillin G potassium (1.6 units/ug, MW = 372), a modest dose for a 10 kg dog or child, contains 0.34 mEq of potassium. Verify this with your own calculation. At this dose, the potassium is not important unless there is renal failure, but consider a 10 to 20 fold increase in dose as may be used in some cases. Also, consider the effect of a rapid iv injection when a very high concentration of potassium may reach the heart. After im or slow iv administration the cardiac effect of the potassium would probably be insignificant if renal function is adequate.

| BMS 445 Intro | | Drug Groups | | E-mail | | Slides / Graphics |

Gordon L. Coppoc, DVM, PhD
Professor of Veterinary Pharmacology
Head, Department of Basic Medical Sciences
School of Veterinary Medicine
Purdue University
West Lafayette, IN 47907-1246
Tel: 317-494-8633Fax: 317-494-0781

Last modified 3:48 PM on 4/3/96 GLC