Biology Reference
In-Depth Information
streamline antimalarial procurement and distribution systems and provide
greater impetus for drug companies to reduce ACT manufacturing costs.
As the cost of ACTs falls and their availability increases, the advantages of
a pragmatic, unified ACT-based treatment protocol for both
P. falciparum
and
P. vivax
in all co-endemic regions becomes compelling (
Douglas et al.,
2010
).
The efficacy of ACT for treating
P. vivax
monoinfection has been assessed
in 13 published clinical trials. Including seven studies of dihydroartemis-
inin + piperaquine (DHA + PIP) (
Ratcliff et al., 2007a
;
Karunajeewa et al.,
2004
,
2008a
,
2008b
;
Hasugian et al., 2007
;
Hung et al., 2004
;
Awab et al.,
2010
), five studies of artemether + lumefantrine (AM + LUM) (
Yohannes
et al., 2011
;
Ratcliff et al., 2007a
;
Karunajeewa et al., 2008b
;
Li et al., 1999
;
Krudsood et al., 2007
), three studies of artesunate + sulfadoxine + pyri-
methamine (AS + SP) (
Tjitra et al., 2002
;
Karunajeewa et al., 2008b
;
Kolac-
zinski et al., 2007
), one study each of artesunate + amodiaquine (AS + AQ)
(
Hasugian et al., 2007
), and pyronaridine with either dihydroartemisinin
(
LeYuan and QingXia, 2001
) or artesunate (
Poravuth et al., 2011
). Most of
these were conducted in Asia in areas known to be under threat from CQR
P. vivax
.
A hallmark of the artemisinin derivatives is their high potency and
ability to affect a rapid reduction of initial parasite biomass, a property
which is apparent in both
P. falciparum
and
P. vivax
(
Pukrittayakamee et al.,
2000
). All of the published ACT clinical trials confirmed the rapid clear-
ance of
P. vivax
asexual stages (
Sinclair et al., 2011
). The main difference
between treatment regimens was high variability in the rates of recurrent
parasitaemia between 28 and 63 days of follow-up. The risk of recurrent
parasitemia was greatest in patients treated with artesunate + sulfadox-
ine + pyrimethamine (67%) (
Karunajeewa et al., 2008b
), artesunate + amo-
diaquine (48%) (
Hasugian et al., 2007
) and artemether + lumefantrine
(57-70%) (
Ratcliff et al., 2007a
;
Karunajeewa et al., 2008b
). Unlike its
utility in assessing
P. falciparum
treatment outcomes, genotyping is of lim-
ited benefit in discriminating the cause of recurrent
P. vivax
parasitae-
mia since these can originate from recrudescence, reinfections or relapse
(
Chen et al., 2007
). Evidence of poor efficacy of monotherapy SP and
amodiaquine suggest that in the case of AS + SP and AS + AQ, high
recurrence rates by day 28 are likely to reflect recrudescence or relapse of
insensitive parasites although one cannot prove this with current geno-
typing methods. The high rates of treatment failure with AM + LUM are
remarkable with 57-70% of Papuan patients having recurrent infection if
