Case Study – Antiviral Drugs

00:00 Let's move on to some questions.

00:03 A 63 year old hemophiliac had contracted hepatitis B from contaminated blood products in the 1980's.

00:11 He stopped his medications against medical advice three months ago.

00:15 And presents now with fulminant transaminitis and jaundice.

00:19 The following are true statements about Hepatitis B in medications.

00:25 A. Interferon alpha acts through tyrosine kinase receptors.

00:29 B. Interferon alpha is quickly absorbed at the injection site.

00:34 C. Interferon alpha inhibits ribonuclease that degrades viral messengerRNA.

00:40 And D. Interferon alpha promotes the formation of natural killer cells.

00:46 So find the true statement.

00:51 Fantastic, you picked D.

00:53 Interferon alpha promotes the formation of natural killer cells.

00:59 Let's move on to the next question.

01:01 A 45 year old male has contracted influenza B.

01:05 The following statements are true: A. Zamanivir is an intranasal spray that may be beneficial for this patient if taken within 24 hours of the onset of symptoms.

01:16 B. Amantadine may be used as a prophylaxis for this patient.

01:20 C. Rimantadine may be beneficial for this patient if taken within 24 hours of the onset of symptoms.

01:28 D. Amantadine is an inhibitor of neuraminidase.

01:32 or E. Zamanivir which acts through blockage of a proton port in the cell wall that prevents acidification of the interior of the virus.

01:45 The answer is A.

01:46 Zamanivir is an intranasal spray that may be beneficial for this patient if taken within 24 hours of the onset of symptoms.

01:53 D is incorrect because amantadine is a blocker of a proton pump in the vesicle wall, that would have allowed transcription with an acidic environment.

02:02 E is incorrect because zamanivir is a neuraminidase inhibitor.

02:07 It does not act on a proton port.

02:09 Therefore, the correct answer is A.

02:14 Let's go on to another question.

02:17 A 34 year old male represents with a painful left eye.

02:21 He has a loss of vision in the left visual field.

02:24 The funduscopic image is displayed on the following slide.

02:28 So there you have the funuscopic image.

02:31 Now let's take a look at our choices here.

02:35 The appropriate treatment for this patient would be A. Valganciclovir 900 mg orally twice a day for 21 days and then once a day.

02:47 B. An intravitreal injection of ganciclovir or foscarnet over 7 to 10 days, then valganciclovir 900 mg twice a day for 21 days or resolution.

03:00 C. Ganciclovir 5mg per kilogram intravenous every 12 hours for 21 days.

03:09 Or D. Oral valganciclovir 900 mg twice a daily for 7 days.

03:16 Which is the right choice? You chose B.

03:22 The intravitreal injection of ganciclovir or foscarnet over 7 to 10 days, then oral valganciclovir 900 mg twice daily for 21 days or until resolution.

03:35 So for some reason and I'm not sure why, examination boards love CMV retinitis.

03:43 When I was writing my exams, it was my undergraduate exam, it was on my board, it was on my internal medicine board exam and it was on recertification exams.

03:52 I'm not sure why it keep showing up but examiners love it.

03:55 It's a good disease to know.

03:57 This patient is having retinitis that is threatening the optic nerve.

04:02 This patient has a loss of vision.

04:03 Systemic therapy is not good enough in these situations.

04:08 So intravitreal injection of a strong antiviral like say valganciclovir would be advised.

04:15 Usually it's given every second day for 7 days followed by systemic therapy.

04:19 Sorry, that should be ganciciclovir or foscarnet and then oral valganciclovir for 21 days.

04:27 Or you can give ganciclovir IV for 21 days too.

04:32 Now treatment would obviously be under the care of an eye specialist who is experienced in this disease.

04:37 Ganciclovir intraocular implants are also sometimes used.

04:41 These are teeny-tiny little pluggets that are actually inserted inside the vitreal cavity.

04:47 And they slowly release ganciclovir overtime.

04:50 So those are also being used as well.

04:54 Now for some reason this type of question always shown up on boards.

05:00 I've seen it when I was doing my undergraduate exams, it showed up again for my licensing exams.

05:05 It showed up again for my internal medicine boards.

05:08 And it showed up once again for my recertification exams.

05:11 So we see it over and over and over again in multiple exam formats.

05:16 So exam boards love CMV retinitis.

05:19 It's a very good disease to know.

05:22 Now remember that this patient is having a retinitis that is threatening his optic nerve.

05:26 He has loss of vision.

05:28 So it's very important that to know that systemic therapy is just not enough in this situation.

05:33 So we want to give an intravitreal injection of a strong antiviral like ganiciclovir.

05:39 And we give it usually every second day for 7 to 10 days.

05:44 It's followed then by systemic therapy.

05:46 So that's where oral valganciclovir can be used for 21 days or alternatively we can use intravenous ganciclovir for 21 days too.

05:55 Now treatment is obviously under an eye specialist.

05:59 This is not something that we manage in a general practitioners clinic.

06:03 Now we also have something called ganciclovir intraocular implants.

06:08 These are teeny-tiny little pluggets that are very hard to see with the naked.

06:12 And they are inserted the vitreal cavity or beside the vitreal cavity.

06:16 And those are obviously put in by an eye surgeon as well.

06:20 Those are very, very effective too for CMV retinitis.

06:24 That's it for our questions.

06:28 I'm sure that you're going to do really well.

06:30 Show them what you know.