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From: "Steve Harris" <>
Subject: Re: Ortho Tri-Cyclen and antibiotics
Date: Sun, 17 Mar 2002 19:52:28 -0700
Message-ID: <a73kvn$976$>

"Rei" <> wrote in message
> I recently went on Ortho Tri-Cyclen, and am also on Zithromax and
> Mepron for lyme disease, and after 7 days of the pill (as it says in
> the guide) stopped using condoms, but now I'm afraid that those
> antibiotics may decrease the effectivness of the pill, even though my
> LLMD told me not to worry about it. Does anyone have any useful
> information about this? Thanks.


Glad you asked.  There are scattered anecdotal reports (here one, there one)
of pregnancies in women taking the pill with nearly every antibiotic you can
name. There are very rare, and I can see no reason to believe any of them,
with the exception of two antimicrobials (see below). Formal tests with a
number of common antibiotics have shown no interaction with birth control
pills. The exceptions are rifampin and griseofulvin, two fairly uncommon
drugs.  Rifampin induce liver metabolism of progestins, and can indeed cause
contraceptive failure with both combination pills and progestin-only pills
(mini-pill). In theory, rifampin can also interfere with progestin implants
(Norplant, etc).

Rifampin is a blood red antibiotic (red capsules) used only in treatment of
TB and TB exposure, and occasionally as prophylactic treatment against
carriage of Neisseria meningitius (menigicoccus). It is taken on an empty
stomach and turns the urine orange. You know it when you're given it.

The other is the antifungal griseofulvin, which is given for months, for
things like toenail fungus. It's rarely used any more, since there are
better drugs. It's cheap, though so I wouldn't put it past HMOs to try it.
It's only used for fungal infections, however, not for common infections.
Again, it's a strange enough antibiotic that you'll know it if you're taking
it, since it will be for something quite unusual like nail fungus.

The case for none of the other common antibiotics is good.  There is a lot
of hysteria.


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