Penicillins

Some basic info…

• Penicillins are bacteriocidal meaning they kill the microorganisms (as opposed to bacteriostatic which only inhibit growth). Therefore, you could use this in an immuno-compromised patient.
• If you’re allergic to one, you’re allergic to all penicillins.
• Narrow to Broad Spectrum: They could go anywhere from narrow to broad spectrum. As we get broader, we run into a greater chance of killing the natural flora and getting a super infection.
• They can also cross the Blood Brain Barrier.

Penicillinase Resistant Penicillins

Penicillinase is an enzyme that breaks down penicillin. Penicillinase is produced by a bacteria that cleaves the bond of the penicillin backbone and renders it useless so the penicillin can’t kill anything. The organism that makes penicillinase is S. aureus. Penicillinase resistant penicillin can’t be broken down by S. aureus (except for MRSA). These feisty MRSA organisms started producing other chemicals that destroy the penicillin.  If we are lucky enough to be able to use this antibiotic, it’s a narrow spectrum so we have a very low chance of a super infection.

Penicillinase Resistant Antibiotics

• Dicloxacillin (Dynapen) – p.o.
• Methicillin (Staphcillin) – inj
• Nafcillin (Unipen) – p.o., inj
• Oxacillin (Bactocil, Prostaphlin) – p.o., inj

Recap

• Resistant to penicillinase enzyme produced by Staph Aureus
• MRSA strains can still destroy this antimicrobial agent
• Narrow Spectrum
  • Staph Aureus
    • Staph causes skin, otitis (infection of hearing canal) and respiratory infections.

Penicillin G’s

They are still fairly narrow but broader than the previous group with a low risk of super infection.

Spectrum:

• Streptococcus pneumonia
  • Respiratory, skin, otitis
• Anaerobic Streptococcus
  • Respiratory
• Neisseria (we can’t use it on this organism anymore as it’s acquired resistance)
  • STD
• Trepenema pallidum (syphilis)
  • STD

Examples of Penicillin G’s

• Penicillin G Potassium (Pentids) – p.o.
• Procaine Penicillin G (Wycillin) – inj
• Penicillin V Potassium (Pen VK) – p.o.

Wider Spectrum Penicillins

Spectrum

The spectrum is the same as the penicillin G’s, except slightly broader in spectrum, so we’re risking super infection a little bit more. These antibiotics can work on all the things the Penicillin G’s do, but also include E. coli, Hemophilus influenza and enterococcus.

• Same as penicillin G’s in addition to…
• E. coli
  • GI, UTI
• Hemophilus influenza
  • Respiratory, otitis infections
• Enterococcus (these are now not only becoming resistant to penicillin but the backup drug Vancomyin, called VRE)
  • GI, UTI

Examples of Wider Spectrum Penicillins:

• Ampicillin (Omnipen) – p.o., inj
• Amoxicillin (Amoxil) – p.o.

Extended Spectrum Penicillins

These are synergistic with aminoglycosides and we get a super powerful effect useful for immuno-compromised patients. The spectrum is the same as the previous penicillins but also includes pseudomonas aeruginosa, a terrible infection. So now we’re adding even more to the spectrum and definitely risking super infection.

• Synergistic with aminoglycosides
• Spectrum
  • Same as previous but includes…
  • Pseudomonas aeruginosa
    • UTI, Respiratory

Examples:

• Ticarcillin (Ticar) – inj.
• Piperacillin (Pipracil) – inj.
• Mezlocillin (Mezlin)

Potentiated Penicillin

Examples:

• Ticarcillin/Clavulanate (Timentin) – inj.
• Amoxicillin/Clavulanate (Augmentin) – p.o.
• Ampicillin/Sulbactam (Unasyn) – inj.
• Piperacillin/Tazobactam (Zosyn) – inj.

For these antibiotics, there’s two chemical agents in each one. One of them ends in -cillin so you know there’s penicillin in it.  The other chemical is a potentiator, a drug that doesn’t have the desired effect but makes the first agent stronger. So by themselves, clavulanate, sulbactam and tazobactam won’t do a thing. However they bind up the enzyme that these resistant organisms produce that destroy penicillin. This allows the penicillin to destroy the organism.  These are utilized when resistance is involved.

So why don’t we use these all the time? Because then they’ll become resistant to these!  The hospital protocol usually says you can’t use these unless there’s documented proof of resistance.  There is one exception where you could use it right away: If you know the infection was acquired in the hospital, a nosocomial infection, then we can immediately start them on this infection because you can assume this is a resistant organism.

Recap

• Examples of potentiators: clavulanate, tazobactam, sulbactam
• Overcomes resistant organisms
• Overcomes enzymes that would destroy the penicillin antimicrobial agent