Oral Contraceptives and Hepatic Metabolism

[Macaroon_Berry]

I know that oral contraceptives are metabolized by P450 enzymes, so P450 inducers decrease the efficacy of the contraceptives, but I just read that "combined oral contraceptives (presumably the estrogen component) can impair the hepatic metabolism of several drugs, prednisone and glucocorticoids among them." Therefore, taking oral contraceptives with prednisone leads to increased prednisone side effects.

I never heard of contraceptives also being P450 inhibitors.. can someone please clarify?

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[Macaroon_Berry]

Actually, I just found this article that explained that the affinity for plasma proteins was higher for contraceptives than it was for glucocorticoids resulting in a known increased glucocorticoid efficacy by estrogen.

http://link.springer.com/article/10.1007/BF00542149#page-1

 

[worldbeater]

I know that oral contraceptives are metabolized by P450 enzymes, so P450 inducers decrease the efficacy of the contraceptives, but I just read that "combined oral contraceptives (presumably the estrogen component) can impair the hepatic metabolism of several drugs, prednisone and glucocorticoids among them." Therefore, taking oral contraceptives with prednisone leads to increased prednisone side effects.

I never heard of contraceptives also being P450 inhibitors.. can someone please clarify?

When they are using the word "impair", I don't think that implies it's a P450 inhibitor. Also if you are saying OCPs lead to an increase in prednisone side effects, you are saying more of the prednisone has been metabolized by the liver, not less. So, not sure what direction your going here.

I've only seen OCPs as inducers, for what it's worth.

 

[Macaroon_Berry]

When they are using the word "impair", I don't think that implies it's a P450 inhibitor. Also if you are saying OCPs lead to an increase in prednisone side effects, you are saying more of the prednisone has been metabolized by the liver, not less. So, not sure what direction your going here.

I've only seen OCPs as inducers, for what it's worth.

Actually, you're totally wrong. The reason why (not all, but most) drugs have increased side effects is not because they have been metabolized but rather because of reduced metabolism, hence an increase in the half-life of the parent drug - the longer the drug stays in the body, the more likely it'll produce side effects. If OCPs lead to an increase in prednisone side effects, it's because less prednisone has been metabolized by the liver, not more. My answer made perfect sense, and it's quite a common way for drugs to have side effects - when they have competition for the plasma protein binding. And I'm not "going" in any direction, I asked a question, for what it's worth.

 

[Phloston]

I couldn't imagine the USMLE ever testing steroids in the context of OCPs. The only thing you'd ever need to know is that certain antibiotics decrease the efficacy of OCPs.

 

[Macaroon_Berry]

I couldn't imagine the USMLE ever testing steroids in the context of OCPs. The only thing you'd ever need to know is that certain antibiotics decrease the efficacy of OCPs.

Thanks Pholston! Btw, I was wondering if you had any other powerpoints to share besides the Micro and antibiotics ones - they were so amazing and you're a huge help!!