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Rich,
On Mon, 30 Sep 1996, Richard Pyle wrote:
> Incidently, isn't it true
> that doxy. is more effective against P. falciparum (the nasty one),
> and Larium is better for P. vivax? Or is it the other way around?
Effective depends on what you are trying to treat: the blood phase or
the liver phase. Doxy is (probably) active against more strains of P
falciparum in red blood cells than is Larium (mefloquin). But this also
has to do with the concentration of mefloquin in the blood. By taling it
only once a week, if you get infected the day or so after your last dose,
falciparum can infect many cells by the time it comes to take your next
dose - a week or so later. Doxy, because it's there every night has a
chance of knocking off the parasites when they are first injected into you
by the mosquito. (In birth control terms - the difference between a condom
and a "morning-after" pill)
P. falciparum doesn't have a liver phase, but P. vivax does. So when you
treat with mefloquin you knock off parasites in both the red cells and the
liver. If you use only doxy, it's (probably) not as effective as mefloquin
for the liver phase - but then your blood didn't get infected in the first
place, right? In practice, many experts recommend that you take a course
of primaquin when you leave the malaria endemic area, to eradicate any
parasites that slipped through your prophylaxis. Others point out that the
chance of a tourist being infected in the first place is so low that the
side effects from this secondary treatment are not worth it. I think it is
worth it for people who have spent a prolonged time in an endemic area,
say several weeks or more in the boonies. But discuss it with you doctor.
Mahalo,
-ph
PS Good to meet you at the forum. My comments on this (the forum) will
follow.
*******************************************************************
* Peter Heseltine, M.D., F.A.C.P. *
* Professor of Medicine *
* University of Southern California LAC+USC Medical Center *
* Tel: 213/226-6705 1200 North State Street *
* Fax: 213/226-2479 Los Angeles, CA 90033-1084 *
* Eml: heseltin@hs*.us*.ed* USA *
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