DTIC ADA263042: Reversal of Plasmodium Falsiparum Resistance to Chloroquine in Panamanian Aotus Monkeys

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An Aotus-Plasmodium faiciparum model was used to ietermine if chioroquine
resistance ctuld be reversed in vivo. The putative resistanqce modul~ators tes-:8a all
reverse chloroquine resi.stance in vitro and included verapami., chlorprcmazine, pinch-
lorperarine, cyprohaptadir.e. Icetatifen, a tiapamil analog (LRo :1-2933), an~d a
chlorpromazine analog (SKI 2133-A). Combinations of chloroquine plus chiorpromazine
or prochiorperazine confirmed reversal of chlorequine resistance as exhibited by cures
obtained in six Aotus monkeys infected with chloroqui~ne-resistant.P.falciParum
(Vietnam Smith/RE strain) and rapid clearance of parasitemia, followed by recrudescence
in six. additional monkeys. The results indicate the following order of in viva
efficacy for reversing ekiloroquine resistance in Actus: Chlorpromazine > prochior-
peinazine > desipramine > Ro 11-2933 (tiapamil ar.alog)> kqtotý`fen. Cyprohoptading
and vezaparnil were not effective in reversing ohioroquine resistance and probable
drug toxicity was observed with these drugs in combinatiot with chioroquine.
17 (UYCASIIAINi Si MIT CLSIFICATIN it. IURI~TY-LASIP7EATON 10 1IMT~ATIONOP A 9 IS*C1,
NIN 1140-01-2SO.I00 saA' omI o .9
Anm.J Irop. Med. Itvg.. 48(l). 1993. pp. 126-133
Copyright c 1993 by The American Society of Tropical Medicine and Hygiene
REVERSAL OF PLASMODIUM FALCIPARUM RESISTANCE TO
CHLOROQUINE IN PANAMANIAN AOTUS MONKEYS
DENNIS E. KYLE, WILBUR K. MILHOUS, AND RICHARD N. ROSSAN
Division of Experimental Therapeutics, Walter Reed Army Institute of Research. Washington, DC:
Gorgas Memorial Laboratory, Panama,P anama
Abstract. An Aotus-Plasmodium falciparum model was used to determine if chloro-
quine resistance could be reversed in vivo. The putative resistance modulators tested all
reverse chloroquine resistance in vitro and included verapamil, chlorpromazine, proch-
lorperazine, cyproheptadine, ketotifen, a tiapamil analog (Ro 11-2933), and a chlorprom-
azine analog (SKF 2133-A). Combinations of chloroquine plus chlorpromazine or proch-
lorperazine confirmed reversal of chloroquine resistance as exhibited by cures obtained in
six Aotus monkeys infected with chloroquine-resistant P. falciparum (Vietnam Smith/RE
strain) and rapid clearance of parasitemia, followed by recrudescence in six additional
monkeys. The results indicate the following order of in vivo efficacy for reversing chlo-
roquine resistance in Aotus: chlorpromazine > prochlorperazine ;: desipramine >> Ro
11-2933 (tiapamil analog) > ketotifen. Cyproheptadine and verapamil were not effective
in reversing chloroquine resistance and probable drug toxicity was observed with these
drugs in combination with chloroquine.
Despite the widespread prevalence of drug- MATERIALS AND METHODS
resistant Plasmodium falciparum, chloroquine
remains an important drug in the treatment of Malaria-naive Panamanian owl monkeys
malaria in many parts of the world.' The dis- (Aotus lemurinus lemurinus) were used as hosts
covery that chloroquine resistance could be re- for chloroquine-resistant P. falciparum, and pre-
versed in vitro by using verapamil suggested a viously described procedures and husbandry
novel approach to combination therapy and practices were followed." The chloroquine-re-
raised hopes that the clinical response to chlo- sistant Vietnam Smith strain was used in the
roquine could be restored.? Numerous com- initial experiments with chloroquine combined
pounds besides verapamil have now been shown with verapamil or SKF 2133-A (a chlorproma-
to reverse chloroquine resistance in vitro,3-6 but zine analog). In subsequent studies, a recrudes-
experience with resistance modulators plus chlo- cent isolate from a Vietnam Smith strain-in-
roquine in vivo is limited. In various mouse ma- fected Aotus monkey treated with chloroquine
laria models, verapamil, cyproheptadine, keto- was used. This strain, designated Vietnam Smitlh/
tifen, and amlodipine have been shown to reverse RE, was more resistant to chloroquine as evi-
S. chloroquine resistance,'- ` but primate in vivo denced by limited effects on parasitemia in Aotus
Sdata versus chloroquine-resistant P. falciparum monkeys receiving 20 mg/kg/day of chloroquine
are limited to a single observation."' In that study, for seven days.
desipramine given in combination with chloro- Each monkey was inoculated intravenously
Squine cleared parasitemia in Aotus monkeys in- with 5 x 106 trophozoites of the chloroquine-
fected with chloroquine-resistant P. falciparum, resistant Vietnam Smith or Vietnam Smith/RE
but in each case the infection eventually recru- strain of P. falciparum. The inoculum size pro-
desced. In this study, we report our results with duced a parasitemia of at least 5 x IO1/mm' by
a series of resistance modulators in a Panaman- the fifth day postinoculation, at which time treat-
"ianA olus-P.f alciparum model. The results con- ment was begun. Stock solutions of water-soluble
firm the reversal of P. falciparum chloroquine drug were prepared at appropriate concentra-
resistance in Aotus and allow for comparison of tions and maintained at 4*C during the course
relative abilities of different compounds to re- of treatment. A suspension of water-insoluble
verse chloroquine resistance, drugs was prepared in 0.3% methylcellulose just
93-06775 126
Iim~limEIl
IN VIVO REVERSAL OF CHLOROQUINE RESISTANCE 127
prior to use. All drugs were administered by gas- attributed to a drug affect. An infection was con-
tric intubation in a volume of 7.0 ml, followed sidered cured if the parasitemia cleared and blood
by a 7.0-ml rinse with either water or 0.3% meth- films remained negative for 100 days after the
ylcellulose. Chloroquine alone or in combination end of treatment. Infections that failed to be cured
with the candidate resistance modulator drug was by the initial treatment were subsequently treat-
given orally for either three or seven consecutive ed with higher doses ofresistance modulator plus
days. In several experiments, the putative resis- chloroquine or with mefloquine. Re-treatment
tance modulator was given three times per day data were not considered in the analysis of drug
(8:00 AM, noon, and 4:00 PM) for three or seven efficacy because of the high rate of self-limiting
days. A 20 mg/kg dose ofchloroquine, given once infections (7 3%) observed in this model. " I Clear
"ad ay for either three or seven days, was used as evidence of drug efficacy can be observed through
"an egative control in all experiments. Adminis- the peak phase of parasitemia, which is up to 8-
tration of chloroquine in either three daily doses 11 days from initiation of patency. Parasitemia j
of 20 mg/kg or seven daily doses of 5-20 mg/ in self-limiting infections begins to decrease 8-
kg is effective at curing infections with chloro- 14 days after initiation of patency."
quine-susceptible parasites in Aotus; however,
these regimens are not effective against the Vi- RESULTS
etnam Smith or Vietnam Smith/RE strains. 12
Giemsa-stained blood smears were prepared Experiments designed to detect the ability of
from all animals and examined daily beginning verapamil to reverse chloroquine resistance in
the day after inoculation until parasitemia was Aotus involved using two different treatment reg-
cleared and for at least seven days thereafter. At imens. In the first experiments, verapamil was
that time, blood films were examined twice a administered at a dose of 25 or 50 mg/kg once
week up to 100 days after treatment. Thick blood a day for three days with or without chloroquine
films were considered negative if no parasites (Figure 1). In Aotus monkeys inlected with the
were seen after examination for at least five min. Vietnl .n Smith strain, parasitemia in two ani-
Ten or less parasites on a thick blood film were mals receiving 20 mg/kg ofchloroquine was not
recorded as < 10. Parasitemia was enumerated significantly affected and one died from malaria
by the Earle-Perez technique' 3 and expressed as (Figure I A). Parasitemia remained high for more
number of parasites/mm3.Treated animals were than seven days subsequent to treatment with 25
observed twice a day for signs of drug toxicity, mg/kg of verapamil alone (Figure 1B ). Parasit-
as evidenced by abnormal behavior, anorexia, emia in each monkey became negative by day
diarrhea, or vomiting. Necropsies were per- 21 post-treatment; however, the rate of parasite
formed on all animals that died. In conducting clearance was equal to that in self-limiting Vi-
the research described in this report, the inves- etnam Smith infections and could not be attrib-
tigators adhered to the Guide for the Care and uted to a drug effect. A three-day dosage of 50
Use of Laboratory Animals, as promulgated by mg/kg of verapamil alone had no effect upon
the National Research Council. parasitemia and both monkeys died of apparent
The classification of treatment outcomes was drug toxicity 4-6 days after the completion of
adapted from Schmidt,'4 and the outcome of each treatment. Two animals received 25 mg/kg of
infection was compared with untreated controls verapamil plus 20 mg/kg of chloroquine (Figure
and monkeys treated with chloroquine or the I C). Parasitemia became negative in both mon-
resistance modulator alone. The infection was keys by day 21 post-treatment, but again at a rate
considered suppressed when parasitemia per- similar to that seen in untreated infections. Two
sisted throughout treatment, but was reduced to monkeys received 50 mg/kg of verapamil plus
less than one-fiftieth the level of parasitemia in chloroquine and both died, one of apparent drug
the control on the same day postinitiation of toxicity and the other of malaria.
treatment. An infection was considered cleared In the second series of experiments with ver-
if the parasitemia became negative by 12 days apamil and chloroquine, the Vietnam Smith/RE
after the infection became patent and remained strain was used and divided doses of verapamil
negative for seven days; clearance ofparasitemia were given to reduce the toxicity observed with
after the infection was patent for 12 days was higher daily doses in the first experiment. Ver-
indicative ofa self-limiti-.g infection and was not apamil (5 mg/kg) was given three times per day
128 KYLE AND OTHERS
R(cid:127), Rx R',
0P
E 100ABC -
E D
T.
100
10
0 CO 202
0 1 AERC o5o 20
0 << .01
D NEG
z I I L I . . . . . I I
246 8 10 02 4 6 8 10 024 6 8
DAY FROM INITIATION OF TREATMENT
FIGURE 1. Activities of verapamil (VER) and chloroquine (CQ) in Aolus monkeys infected with the chlo-
roquine-resistant Vietnam Smith strain of Plasmodiumfalciparum.V ER (25 or 50 mg/kg) (A) and CQ (20 mg/
kg) (B) were given alone or in combination (C) once a day for three days. Each curve represents parasitemia of
an individual monkey. Rx = treatment period; T = monkey treated with an increased dose of VER plus CQ or
with mefloquine; D = monkey died.
(8:00 AM, noon, and 4:00 PM) and chloroquine (Figure 4E). The 20 mg/kg dose of chlorprom-
(20 mg/kg) was given once a day (8:00 AM) for azine plus chloroquine cleared parasitemia in four
three days (Figure 2). Parasitemia was not sig- of four treated monkeys, and cured the infections
nificantly affected in two monkeys given 5 mg/ in three of these (Figure 417). The results were
kg ofverapamil (15 mg/kg/day) plus chloroquine similar when prochlorperazine plus chloroquine
or in two monkeys given chloroquine alone. No was used in the same seven-day treatment regi-
response in parasitemia was seen in monkeys men (Figure 4B and C). Two of two monkeys
administered the same doses ofverapamil alone, were cleared of parasitemia after receiving 10
An analog of tiapamil (Ro 11-2933) that was mg/kg of prochlorperazine and 20 mg/kg ofchlo-
previously shown to reverse chloroquine resis- roquine (Figure 4B). Parasitemia in both mon-
tance in vitro3 was tested in a modified seven- keys recrudesced by day 18 post-treatment. The
day regimen. This analog (20 mg/kg) was given higher dose of prochlorperazine (20 mg/kg) plus
three times per day for seven days and chloro- chloroquine cleared and cured infections of the
quine (20 mg/kg) was administered once a day chloroquine-resistant Smith/RE strain in two
for three days (Figure 3A). Parasitemia was sup- monkeys (Figure 4C). No response in parasit-
pressed in both monkeys receiving the combi- emia was observed when chlorpromazine,
nation treatment, but it began to increase by the prochlorperazine, or chloroquine were admin-
seventh day of treatment. istered alone (Figure 4B-D).
A chlorpromazine analog (SKF 2133-A) that The antihistaminic agents cyproheptadine and
reverses chloroquine and quinine resistance in ketotifen were evaluated in combination with
vitro3 was tested in combination with chloro- chloroquine in a seven-day treatment regimen.
quine in Aotus monkeys (Figure 3B). Parasitemia No significant reduction in parasitemia was seen
was not affected by treatment with either 5 or 10 when either cyproheptadine, ketotifen, or chlo-
mg/kg of SKF 2133-A plus 20 mg/kg of chlo- roquine were given alone (Figure 5B and D). In
roquine given once a day for three days. addition, no response was noted when cypro-
Two additional phenothiazines, chlorproma- heptadine (10 or 20 mg/kg) plus chloroquine (20
zine and prochlorperazine, were evaluated in mg/kg) were given in combination once a day
combination with chloroquine over a seven-day for seven days (Figure 5C). One monkey died of
treatment regimen (Figure 4). The low dose of apparent cardiac toxicity on day 3 of treatment
chlorpromazine (10 mg/kg) plus chloroquine (20 when given 20 mg/kg of cyproheptadine plus
mg/kg) cleared the parasitemia in four of four chloroquine. A slight decrease in parasitemia in
monkeys and cured the infection in one animal one of two monkeys was seen with 10 mg/kg of
L1(cid:127).....
IN VIVO REVERSAL OF CHLOROQUINE RESISTANCE 129
Rx Rx Rx Rx
1000 A ,0oo__ R B 1000 A 0, 0' Co-,- B -
E 100 E 100
10 10
~VERISO
-0. 10 0 0 LA I
M0 _ 1 ' V YENR11 5 0..1 0 N. R. 0 SKF 5
O}o 20 O S.. ..
O 0 7 CO 20 7SK.F 5 ¢020
m <.01 Lmi <.01 V sU 10 C 20
z z
NEG
NEG
0 2 4 6 8 10 0 2 4 6 8 10 02 4 6 8 10 02 4 6 8 10
DAY FROM INITIATION OF TREATMENT DAY FROM INITIATION OF TREATMENT
FIGURE 2. Activities of verapamil (VER) and chlo- FIGURE 3. Activities of Ro 11-2933 (Ro) and SKF
roquine (CQ) in Aotus monkeys infected with the chlo- 2133-A (SKF) alone o- in combination with chloro-
roquine-resistant Vietnam Smith/RE strain of Plas- quine (CQ) in Aotus monkeys infected with the chlo-
modiumfalciparum. VER (5 mg/kg given at 8:00 AM, roquine-resistant Vietnam Smith/RE strain of Plas-
noon, and 4:00 PM, 15 mg/kg/day) and CQ (20 mg/kg modiumfalciparum. Ro (20 mg/kg) was given for seven
given at 8:00 AM) were administered alone (A) or in days (A) and SKF (5 or 10 mg/kg) was administered
combination (B) for three days. Each curve represents for three days (B); chloroquine (20 mg/kg) was given
parasitemia of an individual monkey. Rx = treatment for three days in both experiments. Each curve rep-
period; T = monkey treated with an increased dose of resents parasitemia of an individual monkey. Rx =
VER plus CQ or with mefloquine; D = monkey died. treatment period; T = monkey treated with increased
dose of Ro or SKF plus CQ or with mefloquine.
ketotifen plus chloroquine, whereas suppression cence on days 10-21 post-treatment, was ob-
was observed in one of two animals receiving 20 served in six other monkeys. This represents the
mg/kg of ketotifen plus chloroquine. No mon- first report of cures in an in vivo study using
keys were cleared of parasitemia or cured of in- resistance modulators plus chloroquine against
fection after receiving any combination of either chloroquine-resistant P. falciparum.
cyproheptadine or ketotifen plus chloroquine. Although treatment regimens varied, the pro-
nounced differences in treatment outcomes allow
DISCUSSION for comparison of the relative abilities of can-
didate resistance modulators to reverse chloro-
A Panamanian Aotus monkey-P. falciparum quine resistance in Aotus. Two phenothiazines,
model has been used to determine if the reversal chlorpromazine and prochlorperazine, were the
of chloroquine resistance could be confirmed in most effective at reversing resistance in the .4otus-
vivo with a series of resistance modulators. A P.falciparumm odel. Combinations of these two
previous study demonstrated that the combi- phenothiazines plus chloroquine resulted in the
nation ofdesipramine (50 mg/kg on day one and only cures obtained. An analog of chlorproma-
25 mg/kg on days two and three) plus chloro- zine (SKF 21133-A) that revwrses chloroquine
quine (20 mg/kg for three days) could clear in- resistance in vitro was not effective in this model.
fection with the Vietnam Smith/RE strain; how- The optimal response with ketotifen and a tia-
ever, in each case parasitemia recrudesced by day pamil analog (Ro 11-2933) in combination with
fourteen post-treatment. 10 In this study, the com- chloroquine was the suppression of parasitemia
bination of chloroquine plus chlorpromazine or in Aotus monkeys. Verapamil and cyprohepta-
prochlorperazine confirmed reversal of chloro- dine, both potent reversing agents in vitro.2 1
quine resistance in Aotus. This effect was dem- were not effective in reversing chloroquine re-
onstrated by clearance ofparasitemia and by cures sistance and probable drug toxicity was ob-
obtained in six Aotus monkeys infected with the served. Tt is not known why verapamil and cy-
chloroquine-resistant Vietnam Smith/RE strain. proheptadine did not reverse chloroquine
Clearance of parasitemia, followed by recrudes- resistance in Aotus monkeys, but it could be due
130 KYLE AND OTHERS
AB
h+- (cid:127) • PCPZ 10
o}NoRx ,+CQ 20 P~CCZQ 2200
I V
IL
('~1 V
- N: G I I I',, * -v-v-v V-V
0 2 4 6 8 10 0 2 4 6 8 1 4
'-" x P >x':
< D
~
-- - (cid:127)r '0"//'`."T ,0) 0 CpZ lO ,CO(cid:127) CPZ, O)
0 0.0
C II I
NEG AL-__ -I
0 2 4 6 8 10 0 2 4 6 8 *0 0 2 4 6 10
DAY FROM NITATIA'ON OF TREATMENT
FIGURE 4. Activities of prochlorperazine (PCPZ) and chlorpromazine (CPZ) alone or in combination with
chloroquine (CQ) in Aotus monkeys infected with the chloroquine-resistant Vietnam Smith/RE strain of Plas-
modium falciparum.M onkeys were given 10 or 20 mg/kg of PCPZ or CPZ alone (C and D) or in combination
with 20 mg/kg of CQ (B, C, E, and F) once a day for seven days. Untreated monkeys (A) and animals treated
with CQ alone (B) were used as controls. Each curve represents parasitemia of an individual monkey. Rx =
treatment period; T = monkey treated with an increased dose of PCPZ or CPZ plus CQ; D = monkey died.
to pharmacokinetics or drug metabolism in the Aotus model: chlorpromazine > prochlorpera-
host. These results and those previously zine ý* desipramine :a- Ro 11-2933 > ketotifen.
published10 indicate the following order of in vivo These results suggest that structure-activity re-
efficacy of reversing chloroquine resistance in the lationships for phenothiazines and tricyclic an-
IN VIVO REVERSAL OF CHLOROQUINE RESISTANCE 131
Rx Rx
1000 A B C
100 -1 0y 0-T
O
0CQ 20
1 0NO Rx
10 0CP1
1 V CYP 20
1~ 0 "(cid:127)CYP 10
• + CO 20
0.1 S•j CYP 20
+ CO20
N) <.01
0
X NEG
, I I , I I I I II I I I I I I I I I I
(1) 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10
I--
(/1 Rx Rx Rx
ii1o 00 D EO.. F T
0 100 0
10*0 KTF 20
M(cid:127) 1 0 - KTF 20
• Z 1 • + cQ 20
0.1 0} KTF 20
+ CO 20
<.01
NEG
I I 1 I, I 1 I I It 1
0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10
DAY FROM INITIATION OF TREATMENT
FIGURE 5. Activities of cyproheptadine (CYP) and ketotifen (KTF) alone or in combination with chloroquine
(CQ) in Aolus monkeys infected with the chloroquine-resistant Vietnam Smith/RE strain of Plasmodium. fal-
ciparum. Monkeys were given 10 or 20 mg/kg of CYP or KTF alone (B and D) or in combination with 20 rag/
kg of CQ (C, E, and F) once a day for seven days. An untreated animal (A) and a monkey treated with CQ
alone (B) were used as controls. Each curve represents parasitemia of an individual animal. Rx = treatment
period; T = monkey treated with an increased dose of CYP or KTF plus CQ; D = monkey died.
tidepressants should be conducted. The goal The results obtained in this study with antih-
would be to identify potent resistance modula- istaminics and verapamil contrast with the re-
tors that lack pronounced activities as antipsy- versal of chloroquine resistance demonstrated in
chotics or antidepressants. two mouse malaria models. ." . In the chioro-
132 KYLE AND OTHERS
quine-resistant P. yoelli model, verapamil, cy- in several owl monkeys. The reasons for the
proheptadine, and ketotifen each reverse chlo- deaths of Aotus monkeys 4-6 days after treat-
roquine resistance.57 Verapamil also reverses ment with verapamil alone or in combination
chloroquine resistance in P. chabaudi.8 The con- with chloroquine are unknown. A cardiac-active
trasting results in Aotus and mice could be at- drug such as verapamil would be expected to
tributed to differences in the pharmacokinetics produce more acute toxic effects. Clearly, thor-
of the drug combinations, differences in the route ough studies of pharmacokinetics and acute tox-
of drug administration (oral in monkeys versus icology are needed with chloroquine plus resis-
subcutaneous in mice), differences in the mech- tance modulator combinations before proceeding
anism(s) of chloroquine resistance in P. falcip- to clinical trials.
arum, P. yoelli, and P. chabaudi, or to a com-
bination of these factors. The negative results of Financial support: These studies were supported in part
this study with the combination of ocochruloier oquine bCyo mUm.Sa. nAd rcmoyn trMacet dDicaAl MRDe seIa1r7c-h87 -aCn-d7 1D63e.velopment
plus cyproheptadine are similar to those ob-
served in a clinical study conducted in Africa.'5 Disclaimer: The views of the authors do not purport
Therefore, in both humans and Aotus, the com- to reflect the positions of the U.S. Army or the U.S.
bination ofchloroquine plus cyproheptadine was Department of Defense.
not effective in reversing chloroquine resistance. Authors' addresses: Dennis E. Kyle, Department of
This lack ofeffect could be attributed to very low Immunology and Parasitology, AFRIMS, APO AP
levels of cyproheptadine or cyproheptadine me- 96546. Wilbur K. Milhous, Department of Parasitol-
tabolites found in plasma following oral admin- ogy, Division of Experimental Therapeutics, Walter
istration of the drug. 16 Reed Army Institute of Research, Washington. DC
20307-5 100. Richard N. Rossan, PSC #02 Box 2209,
The in vivo confirmation of the reversal of APO AA 34002.
chloroquine resistance in Aotus reported here is
encouraging and supports the possibility that Reprint requests: Dennis E. Kyle, Department of Im-
eventually resistance modulators may be useful munology and Parasitology. AFRIMS. APO AP 96546.
clinically for the treatment of chloroquine-resis-
tant malaria; however, these data should not be
construed as supporting immediate initiation of REFERENCES
clinical trials with chlorpromazine, prochlorper-
azine, or other resistance modulators with chlo- 1. Campbell CC, 1991. Challenges facing antima-
roquine. Direct extrapolation of data from the larial therapy in Africa. J Infect Dis 163:1207-
1211.
Aotus-P. falciparum model to humans is un- 2. Martin SK, Oduola AMJ. Milhous WK, 1987.
warranted without determining if the pharma- Reversal of chloroquine resistance in Plasmo-
cokinetics of the drugs in combination are sim- dium falciparum by verapamil. Science 235:
ilar in both hosts. In addition, the doses of 899-901.
prochlorperazine used in this study are much 3. Kyle DE, Oduola AMJ, Martin SK. Milhous WK,
1990. Plasmodium falciparum: modulation by
higher than those used in humans and the doses calcium antagonists of resistance to chloroquine.
of chlorpromazine used are close to the highest desethylchloroquine, quinine, and quinidine in
doses used in patients. vitro. Trans R Soc Trop Med Hyg 84:474-478.
The possibility for toxic consequences with re- 4. Basco LK, Ringwald P, LeBras J, 1991. Chloro-
sistance modulator therapy have been suggested quine-potentiating action of antihistaminics in
Plasmodium falciparum in vitro. Ann Trop Med
for the treatment of cancer and malaria.'7. 18 An Parasito18 5: 223-228.
example of this has been shown in schizophrenic 5. Peters W, Ekong R, Robinson BL, Warhurst DC,
patients in Africa receiving chloroquine and 1989. Antihistaminic drugs that reverse chlo-
chlorpromazine. Pretreatment with chloroquine roquine resistance in Plasmodium falciparum.
Lancet ii: 334-335.
markedly increases plasma levels of chlorprom- 6. Basco LK, LeBras J. 1992. In vitro activities of
azine and a major metabolite (7-hydroxychlor- chloroquine in combination with chlorproma-
promazine) in patients to potentially toxic levels zine or prochlorperazine against isolates of Plas-
and influences urinary excretion of the drug.19- 20 modium falciparum. AntimicrobAgents Chem-
other 36: 209-213.
In this study, the results of trials with verapamil 7. Peters W, Ekong R, Robinson BL, Warhurst DC,
and cyproheptadine suggest that combined drug Pan XQ, 1990. The chemotherapy of rodent
toxicity can not be excluded as a cause for deaths malaria. XLV. Reversal of chloroquine resis-
IN VIVO REVERSAL OF CHLOROQUINE RESISTANCE 133
tance in rodent and human Plasmodium by an- 14. Schmidt LH, 1978. Plasmodium falciparum and
tihistaminic agents. Ann Trop Med Parasitol Plasmodium vivax infections in the owl monkey
84: 541-551. (Aotus trivirgatus). 11. Responses to chloro-
8. Tanabe K. Kato M. Izumo A, Hagiwara A, Doi quine, quinine, and pyrimethamine. Am J Trop
S, 1990. Plasmodium chabaudi: in vivo effects Med Hyg 27: 703-717.
of Car' antagonists on chloroquine-resistant and 15. Bjorkman A, Willcox M, Kihamia CM, Mahika-
chloroquine-sensitive parasites. Exp Parasitol wano LF. Phillips-Howard PA, Hakansson A,
70: 419-426. Warhurst DC, 1990. Field study of cyprohep-
9. Deloron P, Basco LK, Dubois B, Gaudin C. Cla- tadin/chloroquine synergism in falciparum ma-
vier F. LeBras J, Verdier F, 1991. In vitro and laria. Lancet 336: 59-60.
in vivo potentiation ofchloroquine against ma- 16. Hintze, KL. Wold JS, Fischer LJ, 1975. Dispo-
laria parasites by an enantiomer of amlodipine. sition of cyproheptadine in rats, mice, and hu-
Antitnicrob Agents Clemother 35." 1338-1342. mans and identification of a stable epoxide me-
10. Bitonti AJ, Sjoerdsma PP, McCann PP, Kyle DE, tabolite. Drug Metab Dispos 3: 1-9.
Oduola AMJ, Rossan RN, Milhous WK, Da- 17. Gottesman MM, Pastan 1, 1988, The multidrug
vidson DE. 1988. Reversal of chloroquine re- transporter, a double-edged sword. JBiolChem
sistance in malaria parasite Plasmodium falcip- 263: 12163-12166.
arumbydesipramine. Science 242: 1301-1303. 18. Watt G. Long GW, Grogl M, Martin SK, 1990.
11. Rossan RN. Harper II JS, Davidson DE Jr, Es- Reversal ofdrug resistant falciparum malaria by
cajadillo A. Christensen HA, 1985. Compari- calcium antagonists: potential for host cell tox-
son of Plasmodium falciparum infections in icity. Trans R Soc Trop MedHvg84: 187-190.
Panamanian and Colombian owl monkeys. A4m 19. Makanjuola ROA, Dixon PAF, Oforah E. 1988.
J Trop Med Hyg 34: 1037-1047. Effects of antimalarial agents on plasma levels
12. Schmidt LH, Vaughan D, Mueller D, Crosby R, ofchlorpromazine and its metabolites in schizo-
Hamilton R. 1977. Activities of various phrenic patients. Trop Geogr .ed 40: 31-33.
4-aminoquinolines against infections with chlo- 20. Oforah E. Dixon PAF. 1983. The influence of
roquine-resistant strains of Plasmodium falcip- drug pretreatment on the metabolic oxidation
arum. Antimicrob Agents Chemother 11: 826- of chlorpromazine in rat. Pharmacology"2 7:
843. 176-179.
13. Earle WC, Perez M, 1931. Enumeration of par-
asites in the blood of malarial patients. J Lab
C(in Med 19: 1124-1130.
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