USMLE Step 2 Review 18 03 Drugs of Choice Zidovudine

USMLE Step 2 Review 18 03 Drugs of Choice Zidovudine

 

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Begin 18 03 Drugs of Choice Zidovudine Transcription

While it is generally accepted now that single-drug therapy of HIV has little long-term benefit, current recommendations still center on 1 drug as the drug of choice for the first step in treatment.

What is the abbreviation it is commonly known by?

  • AZT.

What is the generic name, and correct abbreviation for the drug formerly referred to as AZT?

  • Zidovudine (ZDV).

Trade name for Zidovudine?

  • Retrovir.

What class of drug is ZDV/Retrovir?

  • Nucleoside Reverse Transcriptase Inhibitor.

Again—class of drug for ZDV/Retrovir?

  • Nucleoside Reverse Transcriptase Inhibitor.

What are the 2 major adverse side effects of ZDV/Retrovir? Hint: they are both hematological.

  • Anemia and granulocytopenia.

While many physicians treating HIV choose to start ZDV therapy early, what are the 3 currently recommended indications for beginning ZDV therapy?

  • First, patient is symptomatic, patient CD4 count is below 500, or patient has greater than 100,000 copies of HIV RNA per mL of serum.

Now, HIV treated with ZDV alone quickly develops resistance via mutation, the virus achieving a turnover even during asymptomatic periods of up to a billion new viruses per day. Other nucleoside analogs—reverse transcriptase inhibitors—are often used in combination with ZDV as AIDS progresses, with only modest benefit regarding ultimate outcome. However, what other class of drugs has been tried in combination with ZDV.

Which has had recent reports of outstanding success in reducing viral load by 98% and raising CD4 count by over 100 within 24 weeks?

  • Protease Inhibitors.

And what are 3 Protease Inhibitors?

  • Saquinavir, Ritonavir, Indinavir.

Again, what are 3 Protease Inhibitors currently being tested in combination with ZDV and other Nucleoside Analogs?

  • Saquinavir, Ritonavir, Indinavir.

What’s the trade name for Saquinavir?

  • Invirase.

And the trade name for Ritonavir?

  • Norvir.

And the trade name for Indinavir?

  • Crixavan.

What mineral is deficient in the serum in hypokalemia?

  • Potassium.

What form of potassium is usually used?

  • Potassium Chloride.

When a patient’s clinical course deviates from what you expect during treatment, and you feel sure of your diagnosis, what should you immediately be suspicious of?

  • An adverse reaction to the drug or drug combination.

Now, while there are a number of newer antibiotics which are highly effective and have few reported side effects, what is the argument for continuing to use older antibiotics, such as the penicillins, even though adverse effects occur more frequently?

The argument is that while it may seem that the newer antibiotics have fewer adverse effects, it may just be that we don’t know yet what all of them are. Anytime a physician compares a new drug to an old, the physician must weigh the risk of yet unreported and unexpected adverse effects of the new against the known and expected risks of the old.

Along these lines, what is the most feared reaction to penicillin?

  • Anaphylactic shock.

And what are the 2 drugs of choice to be administered immediately for anaphylactic shock?

  • Oxygen and epinephrine.

What’s the trade name for epinephrine?

  • Adrenaline.

If a penicillin is definitely indicated for a condition, but the patient may be allergic, what strategy may be employed to overcome penicillin allergy?

  • A desensitization schedule of escalating doses.

What 2 drugs may be used to suppress minor reactions as the desensitization progresses?

  • Epinephrine or antihistamine.

What is the most commonly used antihistamine (IV or PO) to suppress minor allergic reactions?

  • Diphenhydramine.

And what’s the trade name for Diphenhydramine?

  • Benadryl.

What class of Penicillins frequently causes a blotchy rash?

  • The aminopenicillins.

Is this blotchy rash, often caused by the aminopenicillins, a true Penicillin anaphylactic allergy, and cause for contraindicating future use of any Penicillins?

  • No, it isn’t even a contraindication for the aminopenicillins, although the difficulty in explaining that to the patient will probably dissuade the physician from attempting to use a Penicillin unless absolutely necessary.

What is the commonly used aminopenicillin?

  • Ampicillin.

Three trade names for Ampicillin?

  • Omnipen, Principen, Unipen.

What particular GI problem has been associated with many antibiotics, and is associated in terms of the Penicillins, most frequently with Ampicillin (which is Omnipen, Principen, or Unipen)?

  • Pseudomembranous colitis.

What organism, able to take over because the normal flora has been eliminated, causes pseudomembranous colitis?

  • Clostridium difficile.

And what class of organisms is Clostridium difficile?

  • It’s an anaerobe; an anaerobic, gram-positive rod.

What is the drug of choice for treating pseudomembranous colitis due to overgrowth of Clostridium difficile?

  • Metronidazole.

What’s the trade name for Metronidazole?

  • Flagyl.

What class of drug is Metronidazole/Flagyl?

  • It’s a Nitroimidazole.

What is the second-line drug of choice for pseudomembranous colitis, but which may cause emergence of resistant enterococci in the gut?

  • Vancomycin.

And what’s the trade name for Vancomycin?

  • Vancocin.

What central nervous system adverse effect can occur after administration of high doses of Penicillins?

  • Seizures.

And what adverse reaction, called Hoigne’s syndrome, can occur immediately, and last up to half an hour after injections of procaine Penicillin G, or benzathine Penicillin G?

  • A neurologic reaction, including bizarre behavior.

Trade name for the injectable mixture of procaine Penicillin G and benzathine Penicillin G?

  • Bicillin.

And the trade name for the injectable form of procaine Penicillin G by itself?

  • Wicillin.

What is the other potentially severe adverse reaction of the Penicillins, in addition to anaphylaxis and neurological reactions?

  • Nephrotoxicity.

Which Penicillin is least likely to cause nephrotoxicity?

  • Nafcillin.

And what class of Penicillin is Nafcillin?

  • It’s a PRSP—it’s one of the Penicillinase-Resistant Synthetic Penicillins.

And what’s the trade name for Nafcillin?

  • Unipen.

Which PRSP (no longer available commercially) was the most likely to cause nephrotoxicity about 5% of the time?

  • Methicillin.

****END OF TRANSCRIPTION****

 

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