Can AZT be taken by pregnant women with AIDS?

Picture courtesy of UNAIDS

Emily Nix (11 AM Micro) found our discussion on selective toxicity and antibiotics very interesting, and wanted to know more about the prophylactic use of antivirals such as AZT when given by HIV+ women to prevent vertical transmission of the virus to their unborn babies. Here is Emily’s summary of what she found out about this critical topic:

After posting a question on our discussion board about pregnant women and AZT treatments, I noticed that there were a lot of “google posts” online about pregnant AIDS patients taking AZT’s.  Because of our discussions in class about AZT affecting DNA synthesis, I began to wonder how a pregnant woman could take AZT without it negatively affecting her baby.  Adults can take AZT because most of our cells are not synthesizing DNA, unlike those of bacteria.  But, a baby would have a much higher DNA synthesis rate than an adult, so couldn’t a fetus therefore be adversely affected?  Since a mother’s blood doesn’t mix with her fetus’s during pregnancy does that mean her baby is safe from negative side effects?   Because I am very interested in doing humanitarian work, especially in Africa where the AIDS rate is high, I decided to do some research on AIDS patients and AZT’s.

The first website I discovered was a drug site that offered information about Zidovudine, a drug which contains AZT.  Zidovudine is given to mothers with HIV so they do not give the virus to their child during the birthing process (Zidovudine, Retrovir, 2010).  I also noticed that the drug information for Zidovudine included dosage amounts for infants and young children too.  I thought this was really interesting, especially since a fetus and a small child would certainly have more developing DNA than an adult, and would therefore be assumed to have more negative side affects from the drug.  Even if a fetus is protected by the fact that his or her mother’s blood does not mix while in utero, a young child would certainly be receiving the “full effects” of drug when taking it “out of utero.”

Next, I decided to pursue a study done on the effects of Zidovudine in pregnancy published by the New England Journal of Medicine.  In this study, it was concluded that while Zidovudine resulted in very adverse effects in mice embryos, overall it did not harm human fetuses (Sperling, et. al, 1992).  Despite this result, it was also taken into consideration that many of the mothers and children treated with Zidovudine during pregnancy were HIV positive, and as a result had many other factors which could affect their baby-both before and after birth.  Additionally, since Zidovudine has not been in use very long, many of its later effects may not be known (Sperling, et. al., 1992).

After learning that in most cases Zidovudine did not negatively affect a fetus, I decided to investigate the logistics of why.  Unfortunately, I could not find any “exact answer” to my question, but I did find some answers as to how exactly Zidovudine works which helped me to form a hypothesis myself about why it does not seem to harm fetuses.

Similar to the AZT facts we discussed in class concerning bacteria, Zidovudine works to limit the ability DNA synthesis to occur (Monson and Schoenstadt, 2010).  Just like bacteria, and any other living thing, viruses need DNA to survive.  However, the HIV virus is different in the fact that it must first change its RNA to DNA to replicate.  This process is done by using the protein reverse transcriptase enzyme.  Zidovudine works in the body to “trick” reverse transcriptase into thinking it is a building block used to make DNA.  When the reverse transcriptase attempts to use the Zidovudine to make DNA, it does not work (Monson and Schoenstadt, 2010).  Based off of this information, I hypothesize that because the Zidovudine is “selectively toxic” to the HIV virus it does not (or has not been proven to) disrupt a human’s DNA synthesis enough to cause drastic side affects-in mother or child.

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About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on March 6, 2012, in Guest Post, Lecture. Bookmark the permalink. 2 Comments.

  1. AZT was first used in Phase I/II/III trials in Africa in pregnant HIV+ women and yes it did prevent transmission to the newborn. I was always skeptical of this approach as it was proven the ‘cocktail’ was needed to keep blood levels down in HIV+patients but the build up of AZT in the blood flow to the placenta etc. seemed to help a great deal and at this stage of development it was all about the T cell /macrophage/monocyte levels in blood and not lymphatic systems etc. etc.

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