Friday, January 14, 2011

Pregnant Humans And Drug Trials

Part 1: FDA Pregnancy Categories: Who Made These UP, Anyhow?
Part 2: What to do, what to do?

Drugs in pregnancy! One of my favorite topics again.

There are currently five categories: A, B, C, D, and X. There is no standardized labeling for lactation. Categories D and X are pretty good: Proven, serious harm in humans. Category X includes retinol, DES, and thalidomide. Category D includes chemo drugs.

Category A is also pretty good, though fairly useless: Proven not to cause harm. They include folic acid and levothyroxine. Great! Folic acid doesn't cause fetal damage! Who knew??

However. B and C are exceedingly useless. What they say is, well, we don't think it'll do anything terrible, maybe, or maybe it will. The FDA states that 2/3 of currently on-the-market drugs are Category C. Tylenol is Category B.

The biggest problem with the system right now- in my opinion- is that it only looks at double-blind studies. In theory, this is an admirable scientific principle. In practice it doesn't work. At high doses, most drugs will harm animals or animal fetuses, and one purpose of animal studies is to determine the dose that causes harm; therefore, most animal studies will show harm. Many, if not most, Category B and C drugs with proven-harm have used a dosage 5-10x the maximum human dose. Try to get that past an IRB for a double-blind study in pregnant humans! In addition, some drugs cannot be double-blinded: insulin, for example, which is a Category B drug.

For functional purposes, these categories tell you almost nothing about whether the drug si safe. Albuterol is Category B. Fluconazole is Category C. Practically all SSRIs are Category C. Blood-pressure medications which are routinely used, as standard-of-care, to treat pregnant women, are Category C.

For many of these drugs, there is a great deal of data in pregnant women, including Drug X vs. Drug Y efficacy studies. There are large pregnancy registries for many, many drugs, which track adverse events, adverse outcomes, and birth defects. However, if it is not double-blind, the FDA will not consider it while assigning categories. If you or your doctor are interested in a drug, well, read through PubMed and look at the registries. Or trust someone's review.

The FDA, by the way, thinks that these categories are confusing and ineffective and wants to change them.

Next: So That Wasn't Helpful, How Do I Know What's Safe Then???

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