Case Studies – Antimycobacterial Agents

by Pravin Shukle, MD

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    00:00 Let's move on to a question.

    00:03 A woman from a first nations reserve in western Alaska presents with cough with flecks of blood in her green sputum.

    00:10 She has a three month history of fatigue, weight loss and poor appetite.

    00:15 Her sputum is identified with microbaterium tuberculosis.

    00:18 There has been one historical case from her reserve without resistance patterns.

    00:24 The appropriate course of action would be A. Initiate isoniazid, rifampin, pyrazinamide and streptomycin.

    00:33 B. Initiate rifampin to treat for 9 months.

    00:37 C. Initiate isoniazid for 18 months.

    00:41 D. Initiate isoniazid, rifampin and pyrazinamide.

    00:46 If the organisms are fully susceptible, pyrazinamide can be stopped in two months.

    00:51 Or E. Initiate pyrazinamide for 18 months.

    00:57 Okay you chose D and that's correct.

    01:01 Now this is a hard question but let's just go through it so that you understand the concept.

    01:07 And when you to the exam you'll feel much more confident answering these kinds of questions.

    01:12 So in areas with less than 4% resistance isoniazid, a three drug combination is actually reasonable.

    01:21 Now the questions on TV will not focus on your intimate knowledge of each of it's drugs, but on the uses and indications.

    01:29 If the patient had come from say an area of high endemic resistance, like South Asia or South East Asia, Somalia or China, a 4 drug regimen is appropriate.

    01:39 Now some people are advocating the 2 drug approach with just isoniazid and rifampin for 9 or 18 months.

    01:47 This is not unreasonable and could be correct.

    01:50 But the reality is that we use the 3 drug combination in almost all cases.

    01:55 So if you are caught with a question that gives you this choice and no other, then the 2 drug approach would be the answer.

    02:02 But in most cases you're going to be given an option for 3 drug approach.

    02:06 And that would probably be the right answer unless they specifically mention resistance.

    02:11 Single drug treatment of active TB is never a reasonable choice on exams or in the TB clinic.

    02:20 Now let's go on to the next question.

    02:24 The woman from question one received the appropriate treatment as part of the regimen, the CDC consultant also added pyridoxine or vitamin B6 to her regimen.

    02:35 What was the purpose of pyridoxine? Now if you're not sure what the first question was, it's just dealing with a woman from a reserve in Alaska who is found to have TB in the sputum.

    02:49 Let's take a look at our choices.

    02:51 A. Pyridoxine will reduce the risk of pulmonary scarring during treatment.

    02:55 B. Pyridoxine will reduce the risk of hepatotoxicity during treatment.

    03:01 C. Pyridoxine will reduce the risk of dental erosions during treatment.

    03:07 D. Pyridoxine will reduce the risk of arrhythmia during treatment.

    03:11 or E. Pyridoxine will reduce the risk of neurotoxicity during treatment.

    03:17 And the answer of course is E.

    03:22 This is a third question in the a string of two.

    03:28 The woman from question 1 was on oral contraceptives.

    03:30 If you've lost two questions, just be aware that she was started on 3 drug regiment for TB and she lives on a reserve with no worrisome resistance patterns.

    03:40 She does not wish to get pregnant.

    03:43 Which drug is most likely to interfere with the oral contraceptive agent? Is it A. Ethambutol, B. Isoniazid, C. Rifampin, D. Pyridoxine or E. Pyrazinamide.

    03:59 Good for you, you chose rifampin.

    04:02 Now rifampin is an important thing to think about.

    04:06 Because rifampin is the prototypical cytochrome inducer.

    04:10 And it is the drug that we talk about, when we're talking about multidrug interactions.

    04:15 So rifampin is going to be the answer in that case.

    04:22 Let's go on to the next question.

    04:24 A 36 year old HIV positive male is tachypneic and hypoxic.

    04:30 His chest X-ray shows right middle lobe infection.

    04:33 He was diagnosed with microbaterium avium complex or MAC.

    04:38 The appropriate treatment is one of the following.

    04:41 Is it A) Clarithromycin with rifabutin.

    04:44 Is it B) Azithromycin with rifabutin.

    04:47 Is it C) Isoniazid with rifabutin.

    04:51 Is it D) Azithromycin or Clarithromycin with ethambutol and rifabutin.

    04:57 Or is it E) Ethambutol, streptomycin, rifampin, isoniazid and penicillin.

    05:04 Good, you chose D.

    05:07 You can choose either azithromycin or clarithromycin with ethambutol and rifabutin as the second and third agents in the treatment.

    05:18 Microbaterium avium complex or MAC was actually first described as Lady Windermere syndrome.

    05:26 Now who is Lady Windermere.

    05:28 She was a character in Oscar Wilde's play.

    05:30 She was one of these very proper people who wouldn't cough or wouldn't expectorate.

    05:35 And actually it was surprisingly common in these women to see right middle lobe pneumonia because it is cough of the junk that was in their lungs.

    05:43 MAC made a come back in the post-AIDS era.

    05:46 It is treated with a 3 drug regimen that includes a macrolide, ethambutol and rifabutin.

    05:52 Infections from other bacteria like microbacterium ulcerans or microbacterium marinum are treated with similar drugs or other antibiotics that are usually not a horribly symptomatic disease.

    06:05 That's it.

    06:07 You completed a very tough section.

    06:09 I'm really proud of you.

    06:11 Now go up to that exam and show them what you know.

    About the Lecture

    The lecture Case Studies – Antimycobacterial Agents by Pravin Shukle, MD is from the course Antimicrobial Pharmacology.

    Author of lecture Case Studies – Antimycobacterial Agents

     Pravin Shukle, MD

    Pravin Shukle, MD

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