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Memorizing Pharmacology Video 4 of 7

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What's the best way to study for Antibiotics?

Antibiotics are one of the mainstays of patient care. Its very important that nurses understand what antibiotics do in relation to the bacteria they are being prescribed for and many sound very similar....so here is a resource.

Memorizing Pharmacology Video 4 of 7

Chapter 4 Immune kicks it up a notch with over 40 drugs to memorize. But like the other chapters, by categorizing them into related groups, we find them easier to remember. I'll continue to stress the importance of knowing the established prefix and suffix by underlining them when appropriate.

OTC antimicrobials

Brand names help us learn OTC medications. For example, Neosporin combines letters from three topical antibiotics: neomycin, polymyxin B, and bacitracin. Abreva, the brand name for docosanol, ab breviates a cold sore.

To further classify the medications in this section, it's easier to use mechanism of action and / or disease state to create only 5 divisions.

Five Divisions

1) Antibiotics affecting the cell wall

A penicillin class antibiotic, amoxicillin, works by affecting bacterial cell walls. However, some bacteria secrete an enzyme - beta-lactamase - that can break down and render amoxicillin ineffective by destroying the beta-lactam ring. In this case, we add clavulanate which augments amoxicillin as combination Augmentin.

Cephalosporins work similarly and have related chemistry. If someone is allergic to penicillins, there's a small chance they will be allergic to cephalosporins. Within the cephalosporin class, it's easiest to use the 5 different generations to outline specific trends in properties. In general, later generations have more gram-negative coverage, are less susceptible to beta-lactamase attack, and more readily cross the blood brain barrier.

Providers often reserve vancomycin as a last line of treatment to avoid resistance. It works to destroy bacterial cell walls by a different mechanism of action making it effective against Methicillin Resistant Staphylococcus aureus (MRSA).

2) Protein synthesis inhibitors - bacteriostatic

Keep in mind bacteriostatic antibiotics don't kill the bacteria, but provide useful coverage. Tetracyclines have the distinct stem -cycline and many, but not all macrolides like azithromycin end with -thromycin.

Be careful; many medications use the stem -mycin, which isn't useful for specific classification. For example, clindamycin is a lincosamide, unrelated to vancomycin, a glycopeptide and azithromycin, a macrolide. The final medication class in this section is oxazolidinone linezolid. We reserve linezolid for the most resistant bacteria, like MRSA and vancomycin resistant enterococci, VRE.

3) Protein synthesis inhibitors - bactericidal

The aminoglycosides amikacin and gentamicin can kill bacteria rather than just impede their reproduction.

4) Antibiotics for urinary tract infections (UTIs) and peptic ulcer disease (PUD)

Sometimes it's easier to go backwards from disease to drug that works against it. Sulfamethoxazole with trimethoprim prevents bacteria from synthesizing folic acid, something humans can ingest.

Fluoroquinolones like ciprofloxacin and levofloxacin end with -floxacin, making them easy to identify. A recent FDA warning reserves fluoroquinolones for more serious infections. Metronidazole, technically an anti-protozoal, finds use in peptic ulcer disease, PUD.

5) Anti-tuberculosis agents

Remember the four medications: rifampin, isoniazid, pyrazinamide, and ethambutol with the "RIPE" acronym. Active TB requires multiple medication therapy with long treatment courses.

Antifungals

We'll use three representative medications to learn antifungals: amphotericin-B, fluconazole, and nystatin. Only fluconazole has a stem, -conazole. Don't confuse this stem with the stem for proton pump inhibitors (PPIs) that we learned in chapter 1, -prazole. Many online resources say "-azole" is the stem, but that word is an organic chemistry moiety. In the next chapter, we learn about cholesterol lowering drugs that have the stem -statin. While nystatin shares those same 6 letters, it is not for cholesterol.

Antivirals - non-HIV

Most antivirals will have "vir" within their generic names. It's a great tool to identify antivirals, but "vir" doesn't tell you what virus the drug is for. In general, viral infections are naturally resistant to medication. Most viruses replicate within our own cells, making them tough to kill without serious side effects. Because of this, antivirals attempt to do 1 of 2 things: prevent us from getting infected in the first place or keep the virus dormant.

Antivirals for influenza A and B share the stem -amivir, making them easy to spot. Antivirals for herpes simplex virus (HSV) and varicella-zoster virus (VSV) include acyclovir and valacyclovir. Notice they both share the -cyclovir stem. We dose valacyclovir less frequently, increasing patient adherence. Respiratory syncytial virus (RSV), a serious risk to neonates especially, responds to the monoclonal antibody palivizumab.

Antivirals - HIV

To best understand HIV antiviral pharmacology, you should visualize from your pathophysiology class how HIV attacks, enters, and reproduces within a human cell. A full explanation of this mechanism is beyond the scope of this article, but let's pick up a few clues as we learn about our available medications.

The first step is to fuse with a human cell. If it can't do this, it can't replicate. One medication, enfuvirtide, is a fusion inhibitor and literally inhibits viral fusion or connection with our cell. Try to remember that the letter "f" in enfuvirtide stands for "fusion." Another antiviral, maraviroc, blocks a specific receptor CCR5. Use the "c" and "r" to help remember this mechanism for CCR5.

We treat HIV with multiple drugs to prevent resistance. Efavirenz / emtricitabine / tenofovir helps patients stay compliant with their meds. The brand name, Atripla, has part of "triple" in it, reminding us there are 3 drugs in a single pill.

After the HIV gets into the cell, it needs to integrate itself into our DNA with the enzyme integrase. You can see the similarity between raltegravir and integrase to remember this connection. Darunavir is another antiviral inhibiting actions of protease. While the -navir stem bears no resemblance to protease, its brand name Prezista does as "resisting protease." Here are the antimicrobials to make the classifications globally clearer.

OTC antimicrobials

  • Neomycin/ polymyxin B / bacitracin
  • Butenafine
  • Influenza vaccine
  • Docosanol

Antibiotics affecting cell walls

  • Penicillins
    • Amoxicillin
    • Amoxicillin with clavulanate
    • Clavulanate is a beta lactamase inhibitor, augmenting the antibiotic
  • Cephalosporins
    • Cephalexin - 1st generation
    • Ceftriaxone - 3rd generation
    • Cefepime - 4th generation
  • Glycopeptide
    • Vancomycin

Protein synthesis inhibitors- bacteriostatic

  • Tetracyclines
    • Doxycycline
    • Minocycline
  • Macrolides
    • Azithromycin
    • Clarithromycin
    • Erythromycin
  • Lincosamide
    • Clindamycin
    • Watch out for diarrhea / CDAD
  • Oxazolidinone
    • Linezolid

Protein synthesis inhibitors - bactericidal

  • Aminoglycosides
    • Amikacin
    • Gentamicin

Antibiotics for UTIs and PUD

  • Dihydrofolate reductase inhibitors
    • Sulfamethoxazole / trimethoprim
  • Fluoroquinolones
    • Ciprofloxacin
    • Levofloxacin
  • Antiprotozoal
    • Metronidazole

Anti-tuberculosis agents

  • Rifampin
  • Isoniazid
  • Pyrazinamide
  • Ethambutol

Antifungals

  • Amphotericin-B
  • Fluconazole
  • Nystatin

Antivirals - non-HIV

  • Influenza A and B
    • Oseltamivir
    • Zanamivir
  • HSV/VSV
    • Acyclovir
    • Valacyclovir
  • RSV
    • Palivizumab

Antivirals - HIV

  • Fusion inhibitor
    • Enfuvirtide
  • CCR5 antagonist
    • Maraviroc
  • NNRTI w/two NRTIs
    • Efavirenz / emtricitabine / tenofovir
  • Integrase inhibitor
    • Raltegravir
  • Protease inhibitor
    • Darunavir

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Pharmacology Professor

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