Open randomized study of artesunate-amodiaquine

vs. chloroquine-pyrimethamine-sulfadoxine for the treatment

of uncomplicated Plasmodium falciparum malaria in Nigerian

children

A. Sowunmi, F. A. Fehintola, A. A. Adedeji, G. O. Gbotosho, E. Tambo, B. A. Fateye, T. C. Happi andA.M. J. Oduola

Department of Pharmacology and Therapeutics, Institute for Medical Research and Training, University of Ibadan, Ibadan, Nigeria

Summary background Artemisinin-based combination antimalarials are currently considered effective

alternatives for the treatment of malaria in Africa, but there are few studies of such combinations in

Nigerian children. We assessed the safety, treatment efficacy and effects on gametocyte carriage of the

combination of artesunate plus amodiaquine and chloroquine plus pyrimethamine-sulfadoxine in

children.

methods We evaluated 153 children who were aged 12 years or younger who had uncomplicated

Plasmodium falciparum malaria. Patients were randomly assigned a combination of artesunate (4 mg/kg

of body weight daily for 3 days) plus amodiaquine (30 mg/kg over 3 days), or chloroquine (25 mg/kg

over 3 days) plus pyrimethamine-sulfadoxine (25 mg/kg of the sulfadoxine component at presentation).

The primary endpoints were the proportions of children with adequate clinical and parasitological

response, late parasitological failure, late clinical failure and early treatment failure. The parasitological

cure rates on days 14–28 were also used as the primary endpoints.

results Both regimens were well tolerated; no child was withdrawn because of drug intolerance. All

children treated with artesunate plus amodiaquine had adequate clinical and parasitological response

(ACPR), while all but five children treated with chloroquine plus pyrimethamine-sulfadoxine had

similar response. Fever clearance times were similar in the two treatment groups. However, the pro-

portion of patients whose parasitaemia cleared by day 2 was significantly higher (100 vs. 50%,

P ¼ 0.00001) and parasite clearance was significantly faster (1.7 ± 0.4 vs. 2.5 ± 0.8 days, P ¼ 0.0001)

in children treated with artesunate plus amodiaquine. The cure rates on days 21 (100% vs. 94%,

P ¼ 0.03) and 28 (100% vs. 90%, P ¼ 0.003) were also significantly higher in children treated with

artesunate plus amodiaquine than in those treated with chloroquine plus pyrimethamine-sulfadoxine.

Overall, a significantly higher proportion of children treated with chloroquine plus pyrimethamine-

sulfadoxine carried gametocytes at least once during follow-up compared with those treated with

artesunate plus amodiaquine [5 of 50 (10%) vs. 1 of 103 (0.97%), P ¼ 0.01].

conclusion The combination of artesunate plus amodiaquine is therapeutically superior to a

combination of chloroquine plus pyrimethamine-sulfadoxine, and significantly reduced gametocyte

carriage following treatment.

keywords artesunate-amodiaquine, chloroquine-pyrimethamine-sulfadoxine, malaria, children, Nigeria

Introduction

Drug resistance in Plasmodium falciparum to chloroquine

or pyrimethamine-sulfadoxine monotherapy (Sibley et al.

2001) is a major public health problem in much of

sub-Saharan Africa and is a cause of recent increases in

malaria–related morbidity and mortality in African

children (Trape et al. 1998; Trape 2001). In Nigeria,

despite the prevalence rates of chloroquine, pyrimethamine-

sulfadoxine and chloroquine plus pyrimethamine-sulfa-

doxine resistance of 35%, 17–25% and 0%, respectively

(Sowunmi et al. 2001,2004a; Sowunmi 2002,2003), the

public health policy is to treat uncomplicated malaria

episodes with chloroquine, and to use pyrimethamine-

sulfadoxine as the second line drug for those not responding

to chloroquine.

Tropical Medicine and International Health doi:10.1111/j.1365-3156.2005.01503.x

volume 10 no 11 pp 1161–1170 november 2005

ª 2005 Blackwell Publishing Ltd 1161

As alternatives to chloroquine or pyrimethamine-

sulfadoxine, particularly in areas where the parasite is

reasonably sensitive to chloroquine and pyrimethamine-

sulfadoxine, it has been suggested that both drugs be used

in combination, or in combination with other antimalarials

that have modes of action different from those of

chloroquine and pyrimethamine-sulfadoxine, with the aims

of slowing the progression of resistance to these drugs and

prolonging their lifespan (von Seidlein et al. 2000; Basco

et al. 2002; Sowunmi 2002; Drakeley et al. 2003; Gasasira

et al. 2003). An additional antipyretic effect is produced by

combining chloroquine with pyrimethamine-sulfadoxine

(Hugosson et al. 2003).

As a response to the World Health Organization

recommendation (WHO 2001), many African countries

are considering the use of artemisinin-based combinations

as alternatives to monotherapy with chloroquine or pyri-

methamine-sulfadoxine, requiring the revision of treatment

policies in endemic areas. Although artemisinin-based

combinations are effective and safe for use in children in

many countries in Africa (Adjuik et al. 2002), there is a

need to further study the efficacy and safety of these

combinations in different population groups.

Experience with the use of artemisinin-based combina-

tions is relatively limited in West Africa (von Seidlein et al.

2000,2001a,b; Adjuik et al. 2002) making it imperative to

evaluate their efficacies in other settings in sub-Saharan

Africa. Although the effects of artemisinin-based combi-

nations on asexual parasites have been assessed previously

in Nigeria (Sowunmi et al. 1998,2001), to date, in Nigeria,

no study has examined, clinically, the effects of artemis-

inin-based combinations on both asexual and sexual

parasites and compared it with a combination of chloro-

quine plus pyrimethamine-sulfadoxine. Such a study is

essential as it may influence policy and management of

drug resistance in the community.

The main aim of this study was to evaluate the safety,

antimalarial treatment efficacy, and effect on gametocyte

carriage of artesunate plus amodiaquine and chloroquine

plus pyrimethamine-sulfadoxine-combinations in children

aged 12 years or below with acute, symptomatic,

uncomplicated, falciparum malaria.

Materials and methods

Study area

The study was conducted in Ibadan, Southwest Nigeria

from July to December 2004. In this area of hyperendemic

malaria, transmission occurs all year round but is more

intense during the rainy season from April to October.

In the area, it is difficult, clinically, to distinguish

recrudescence from re-infection 14 days after commencing

antimalarial treatment, and traditionally, antimalarial

efficacy tests have usually been conducted for 14 rather than

the customary 28 days (Ekanem et al. 1987; Salako et al.

1990). The prevalence of chloroquine and pyrimethamine-

sulfadoxine resistance in the area (35% and 17–25%,

respectively) has been described recently (Sowunmi et al.

2004a). However, in vivo resistance to amodiaquine is low

(about 1–2%, Sowunmi et al. 2001; Sowunmi 2002).

Patients, treatment and follow up

Patients were eligible to join the study if they were: aged

12 years or younger, had symptoms compatible with acute

uncomplicated malaria, with pure P. falciparum parasitae-

mia >2000 asexual forms/ll, a body (axillary) temperature

>37.4 �C or history of fever in the 24–48 h preceding

presentation, absence of other concomitant illness, no his-

tory of antimalarial use in the 2 weeks preceding presenta-

tion, negative urine tests for antimalarial drugs (Dill-Glazko

and lignin), and written informed consent given by parents

or guardians. Patients with severe malaria (WHO 2000),

severe malnutrition, serious underlying diseases (renal, car-

diac or hepatic), and known allergy to study drugs were

excluded from the study. The protocol was approved by the

Ethics Committee of Oyo State Ministry of Health, Ibadan,

Nigeria. The disease history, taken by the attending physi-

cian, was recorded by asking patients or their parents when

the present symptomatic period had started, and was fol-

lowed by a full physical examination by the same physician.

Enrolled patients were randomly assigned artesunate

4 mg/kg of bodyweight daily for 3 days plus amodiaquine

(30 mg/kg over 3 days) (Larimal�, Ipca Pharmaceutical

Nigeria Plc) or chloroquine (May & Baker, Nigeria Plc)

25 mg/kg of body weight over three days plus pyrimeth-

amine-sulfadoxine (Fansidar�, Swipha Nigeria Plc)

25 mg/kg of body weight of the sulfadoxine component at

presentation (day 0). All drugs were given orally, as single

daily doses, and were administered in the clinic. All patients

waited for at least 3 h after drug administration to ensure

the drugwas not vomited. If it was, the patient was excluded

from the study. If necessary, patients were provided with

antipyrectics (paracetamol tablets, 10–15 mg/kg 8 h for

24–48 h). The randomization was computer-generated and

treatment codes were sealed in individual envelopes. Once

enrolled, study drugs were administered to patients by a

physician. Patient evaluation and follow up after drug

administration was performed by another physician blinded

to the drug treatment. The study nurse obtained thick and

thin blood films from each child as soon as they came to the

clinic. The slides were carefully labelled with the patients’

codes and were air dried before being stained.

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Follow up with clinical and parasitological evaluation

was done daily for 7 days (days 1–7) and then on days 14,

21 and 28. This consists of enquiry about the patient’s well

being, presence or absence of initial presenting symptoms,

presence of additional symptoms, measurement of body

temperature, heart and respiratory rates, and a blood

smear for the quantification of parasitaemia.

Side effects were defined as symptoms and signs that first

occurred or became worse after treatment was started. Any

new events occurring during treatment were also consid-

ered as side effects.

Thick and thin blood films prepared from a finger prick

were Giemsa-stained and were examined by light micros-

copy under an oil-immersion objective, at · 1000 magni-

fication, by two independent assessors who did not know

the drug treatment of the patient. A senior member of the

study team reviewed the slides if there was any disagree-

ment between the microscopists. In addition, the slides of

every third child enrolled in the study were reviewed by this

senior member. Parasitaemia (asexual or sexual) in thick

films was estimated by counting asexual or sexual parasites

relative to 1000 leukocytes, or 500 asexual or sexual

forms, whichever occurred first. From this figure, the

parasite density was calculated assuming a leukocyte count

of 6000/ll of blood.Routine haematological (haematocrit) and biochemical

tests (concentrations of alanine aminotransferase, aspartate

aminotransferase, bilirubin and creatinine) were performed

in 50 randomly selected children (using an autoanalyser),

pre-treatment and on day 14 to detect any drug-associated

effects.

Blood was spotted on filter papers on days 0, 3, 7, 14, 21

and 28, and at the time of treatment failures for parasite

genotyping. Parasite genotyping was done as previously

described (Happi et al. 2003,2004). PCR blots were

analysed for merozoite surface protein 2 (MSP 2) using

block 3 of MSP 2 in patients with recurrent parasitaemia

after day 14.

Response to drug treatment was assessed using WHO

1973 criteria as follows: S, sensitive, clearance of parasit-

aemia without recurrence; RI (mild resistance), parasitae-

mia disappears but reappears within 7–14 days, RII

(moderate resistance), decrease of parasitaemia but no

complete clearance from peripheral blood; RIII (severe

resistance), no pronounced decrease or increase in para-

sitaemia at 48 h after treatment. In those with sensitive or

mild resistance, parasite clearance time was defined as the

time elapsing between drug administration and absence of

detectable parasitaemia for at least 48 h. Fever clearance

time was defined as the time from drug administration until

the body temperature fell to or below 37.4 �C and

remained so for 48 h. Response to drug treatment was also

classified according to a modified version of the WHO

14-day in vivo clinical classification system (WHO 2003);

because not all patients were febrile at enrolment, a

temperature <37.5 �C was not an exclusion criterion for

enrolment. The modification also involved a follow up for

28 days in this area of intense transmission.

Cure rates were defined as the percentages of patients

whose asexual parasitaemia cleared from peripheral blood

and who were free of patent asexual parasitaemia on days

14, 21 and 28 of follow up. The cure rates on days 21 and

28 were adjusted on the basis of the PCR genotyping

results of paired samples for patients with recurrent

parasitaemia after day 14 of commencing treatment. In

patients with recurrent parasitaemia after day 14, those

with matching genotypes on day 0 and the day of

recurrence were classified as treatment failure; those with

mismatching genotypes were classified as cured.

Re-treatment of drug treatment failures

Patients failing treatment (within 14 days) with chloro-

quine plus pyrimethamine-sulfadoxine were re-treated with

artesunate plus amodiaquine and were followed for

another 28 days. Patients were re-treated whenever they

became symptomatic (usually between 14 and 21 days

after initial enrolment). Patients with profound clinical

(hyperpyrexia, oral fluid intolerance) and parasitological

deterioration during follow up were treated with

parenteral artemether (9.6 mg/kg, over 5 days) and were

regarded as treatment failures.

Data analysis

The sample size was calculated so that the study would be

able to detect a 20% absolute difference in parasitological

failure ‘rate’, between artesunate plus amodiaquine and

chloroquine plus pyrimethamine-sulfadoxine groups with

95% power and at a 5% significance level [The expected

treatment success ‘rates’ were 80% for artesunate plus

amodiaquine and 100% for chloroquine plus pyrimeth-

amine-sulfadoxine, based on a relatively recent study

(Sowunmi 2002)]. Randomization was done with a ratio

2:1, amodiaquine plus artesunate: chloroquine plus pyri-

methamine-sulfadoxine. Data were analysed using Version

6 of the Epi-Info software (Anonymous 1994). Variables

considered in the analysis were related to the densities of

P. falciparum gametocytes and trophozoites. Proportions

were compared by calculating chi2 with Yates’ correction

or by Fisher exact or by Mantel Haenszel tests. Normally

distributed, continuous data were compared by Student’s

t-tests and analysis of variance (anova). Data not con-

forming to a normal distribution were compared by the

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A. Sowunmi et al. Artesunate-amodiaquine for uncomplicated malaria

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Mann–Whitney U-tests and the Kruskal–Wallis tests (or by

Wilcoxon ranked sum test). All tests of significance, except

where specifically indicated, were two-tailed. A P < 0.05

were taken to indicate significant differences. Data were

(double)-entered serially using the patients codes and were

only analysed at the end of the study.

Results

Patients’ characteristics

One hundred and fifty-five children were enrolled, 104

were treated with artesunate plus amodiaquine and 51

with chloroquine plus pyrimethamine-sulfadoxine. One

child from the artesunate plus amodiaquine group

was lost to follow up after day 7 because of parental

relocation. Another child in the chloroquine plus

pyrimethamine-sulfadoxine treatment group was given

amodiaquine by her mother on day 6. In both

children, parasitaemia cleared before day 3. These

children were excluded from the data analysis. Figure 1

shows the trial profile. Overall results are for 153

children. The demographic and clinical characteristics

of patients at enrolment are shown in Table 1.

These characteristics were similar in the two treatment

arms.

412 children screened

250 children with patent parasitaemia

155 children enrolled and randomized

104 assigned artesunate plus amodiaquine

51 assigned chloroquine plus pyrimethamine-sulfadoxine

1 excluded 1 excluded

0 treatment failure 2 treatment failures

103 evaluable on day 14 50 evaluable on day 14

0 treatment failure 1 treatment failure

103 evaluable on day 21 50 evaluable on day 21

0 treatment failures 2 treatment failures

103 evaluable on day 28 50 evaluable on day 28

Figure 1 Trial profile.

Tropical Medicine and International Health volume 10 no 11 pp 1161–1170 november 2005

A. Sowunmi et al. Artesunate-amodiaquine for uncomplicated malaria

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Fever and parasite clearance and gametocyte carriage

Eighty-three children were febrile at enrolment, 56 in

artesunate plus amodiaquine and 27 in chloroquine plus

pyrimethamine-sulfadoxine groups. On the whole, 36 of

the children treated with artesunate plus amodiaquine, and

21 of those treated with chloroquine plus pyrimethamine-

sulfadoxine received paracetamol during the first 36 h. By

day 1, fever cleared in 53 children in the first group and in

26 children in the second group, without a significant

difference in the proportion of patients whose fever cleared

by day 1 (v2 ¼ 0.001, P ¼ 0.95). Overall, fever clearance

was similar in both treatment arms (1.1 ± 0.2 vs.

1.0 ± 0.2 days, P ¼ 0.7) (Table 2).

Compared with chloroquine plus pyrimethamine-sulfa-

doxine, artesunate plus amodiaquine substantially accel-

erated the clearance of parasitaemia. By day 2, all 103

children in the artesunate plus amodiaquine and 25 of the

50 children in the chloroquine plus pyrimethamine-sulfa-

doxine treatment arms had cleared their parasitaemias.

The difference in this proportion was significant

(v2 ¼ 57.9, P ¼ 0.000001). Overall, parasite clearance

was significantly shorter in those treated with artesunate

plus amodiaquine (1.7 ± 0.4 vs. 2.5 ± 0.8, P ¼ 0.0001)

(Table 2). The cure rate on day 14 was similar in the two

treatment arms (100% vs. 96%, P ¼ 0.1, by Fisher exact

test). However, cure rates in children treated with artesu-

nate plus amodiaquine were significantly higher on days 21

and 28 than in those treated with chloroquine plus

pyrimethamine-sulfadoxine (100% vs. 94%, P ¼ 0.03,

and 100% vs. 90%, P ¼ 0.003, respectively, by Fisher

exact test). Response to both treatment regimens was not

related to age: no child from the 26 and 77 <5 and ‡5-yearold, respectively treated with artesunate plus amodiaquine

failed treatment by day 28. Similarly, 2 and 3 children from

the 24 and 26 <5 and ‡5-year old, respectively treated with

chloroquine plus pyrimethamine-sulfadoxine failed treat-

ment by day 14 (P ¼ 0.6, by Fisher exact test).

All patients treated with artesunate plus amodiaquine

had ACPR. In those treated with chloroquine plus pyri-

methamine-sulfadoxine, 45 had ACPR and five had late

clinical failure (LCF).

Gametocyte carriage at enrolment in those treated with

artesunate plus amodiaquine was similar to those treated

with chloroquine plus pyrimethamine-sulfadoxine [1 of

103 (0.97%) vs. 1 of 50 (2%), P ¼ 0.5, by Fisher exact

test]. Similarly, carriage on day 7 was similar with both

treatment regimens [1 of 103 (0.97%) vs. 1 of 50 (2.0%),

P ¼ 0.5, by Fisher exact test). None of the patients without

gametocytaemia at enrolment who were treated with

Table 1 Demographic and clinical

characteristics of patients at enrolment Artesunate-

amodiaquine

Chloroquine plus

pyrimethamine-sulfadoxine P value

No. of patients 103 50 –

Male/female 56/47 23/27Age (years)

Mean ± SD 6.7 ± 3.1 5.9 ± 2.9 0.07

Range 1–12 0.9–11.5

No. <5 years 26 24Weight (kg)

Mean ± SD 19.3 ± 7.3 17.9 ± 6.7 0.16

Range 7–47 8–36

Duration of illness (days)Mean ± SD 2.8 ± 1.7 2.9 ± 1.3 0.72

Range 1–7 1–14

Temperature (�C)Mean ± SD 37.9 ± 1.2 38.0 ± 1.1 0.96

Range 36.0–40.5 36.2–40.7

Parasite count (per ll)Geometric mean 32173 43757 0.06Range 2024–395410 2196–1792000

Haematocrit (%)

Mean ± SD 31.1 ± 5.9 31.8 ± 4.7 0.56

Range 18–39 22–42No. <30% 19 11

Enlarged organ

Hepatomegaly 20 12Splenomegaly 36 15

Hepatosplenomegaly 15 5

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artesunate plus amodiaquine carried gametocytes during

follow up. Overall, five patients in the chloroquine plus

pyrimethamine-sulfadoxine were gametocytaemic at least

once during follow-up period as compared to only one

patient in the artesunate plus amodiaquine group. The

difference between the two proportions was significant [5

of 50 (10%) vs. 1 of 103 (0.97%), P ¼ 0.01, by Fisher

exact test]. One of the five gametocytaemic patients treated

with chloroquine plus pyrimethamine-sulfadoxine had

resistance response.

Response to artesunate plus amodiaquine of children with

chloroquine plus pyrimethamine-sulfadoxine treatment

failures

All five patients who failed treatment with chloroquine

plus pyrimethamine-sulfadoxine responded promptly to

re-treatment with artesunate plus amodiaquine. Fever

cleared in all five patients within 24 h of commencing

treatment with artesunate plus amodiaquine and parasit-

aemia cleared within 48 h of treatment with this combi-

nation. The cure rate on day 28 of re-treatment was 100%.

PCR findings in patients with recurrence of parasitaemia

after day 14

Three of five matched sample pairs collected before and

after treatment from patients who failed treatment were

successfully analysed at msp-1 or msp-2 polymorphic loci.

Alleles were classified according to the size of PCR

fragments. Analysis of genotypes of paired pre- and post-

treatment isolates from these three showed that in all the

patients, paired PCR fragments were identical at either

FC27 or IC1 allelic families of msp-2 and K1, MAD20 or

Table 2 Therapeutic responses to

artesunate plus amodiaquine or chloro-

quine plus pyrimethamine-sulfadoxineArtesunate-

amodiaquine

Chloroquine pluspyrimethamine-

sulfadoxine P value

No. of patients 103 50 –

Fever clearance time (days)

Mean ± SD 1.1 ± 0.2 1.0 ± 0.2 0.72Range 1–2 1–2

No. of patient with parasitaemia on day 1 75 47 0.004

No. of patient with parasitaemia on day 2 0 25 0.000001

Parasite clearance time (days)Mean ± SD 1.7 ± 0.4 2.5 ± 0.8 0.0001

Range 1–2 1–5

Day 14 responses

No. cured 103 48 0.1No. RI 0 2

No. RII 0 0

No. RIII 0 0Cure rate (%) 100 96

Day 21 responses

No. cured 103 47 0.03

No. RI (cumulative) 0 3No. RII 0 0

No. RIII 0 0

Cure rate (%)* 100 94

Day 28 responsesNo. cured 103 45 0.003

No. RI (cumulative) 0 5

No. RII 0 0

No. RIII 0 0Cure rate (%)* 100 90

ACPR 103 45 0.003

LPF 0 0LCF 0 5

ETF 0 0

* PCR-corrected ACPR, adequate clinical and parasitological response; LPF, late

parasitological failure; LCF, late clinical failure; ETF, early treatment failure.

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A. Sowunmi et al. Artesunate-amodiaquine for uncomplicated malaria

1166 ª 2005 Blackwell Publishing Ltd

RO33, indicating genuine recrudescent infections after

treatment. In addition, these fragments indicated mono-

clonal infections in all the three patients. Although DNA

amplification in the remaining two patient isolates was not

successful, we considered resurgence of infections in these

patients as genuine recrudescence, because these two

patients re-presented clinical symptoms of malaria on day

14 when they would most likely have adequate blood

concentrations of the drug that could clear sensitive

infections.

Adverse events

Artesunate plus amodiaquine and chloroquine plus pyri-

methamine-sulfadoxine were well tolerated; no child was

withdrawn because of drug intolerance. Symptoms repor-

ted within the first week and during follow up were similar.

Pruritus, vomiting, abdominal pain, anorexia, cough and

headache were reported by 1, 8, 6, 2, 3 and 3 children,

respectively treated with artesunate plus amodiaquine. In

those treated with chloroquine plus pyrimethamine-sul-

fadoxine, 4, 2 and 1 child, reported pruritus, vomiting and

abdominal pain, respectively. Pruritus was significantly

more frequently reported by those treated with chloroquine

plus pyrimethamine-sulfadoxine (P ¼ 0.04) than by those

treated with artesunate plus amodiaquine. One child

treated with chloroquine plus pyrimethamine-sulfadoxine

had generalized macular eruptions on day 2 of treatment.

There was no mucosa involvement in this child, and there

was no family history of skin reaction to sulfonamides. The

eruptions resolved in 1 week without treatment. None of

the five children who failed initial treatment with chlo-

roquine plus pyrimethamine-sulfadoxine and were

re-treated with amodiaquine plus artesunate reported

adverse symptoms.

Haematological and biochemical parameters

Except for haematocrit values below 30% at enrolment in

19 and 9 children in artesunate plus amodiaquine and

chloroquine plus pyrimethamine-sulfadoxine, respectively,

and at day 7 in 10 and 4 children, respectively, haemato-

logical, biochemical and other parameters remained nor-

mal before and after treatment in all subjects (normal

biochemical parameters for the area: ALT 0–40 i.u/l; AST:

0–37 i.u/l; serum creatinine: 0.5–1.5 mg/dl; serum biliru-

bin: 0.5–1.0 mg/dl). Thrombocytopenia, defined as platelet

count <150 · 103 mm3, was present in 15 and 6 children

in artesunate plus amodiaquine and chloroquine plus

pyrimethamine-sulfadoxine, respectively, at enrolment, but

was not seen on day 14 in any child (normal value for the

area: 150–390 · 103 mm3).

Discussion

Artemisinin-based combination antimalarials are currently

favoured by the World Health Organization for use in

Africa (WHO 2001), but there are needs to consider

potential non-artemisinin-based combinations including

amodiaquine- or pyrimethamine-sulfadoxine-based com-

binations in resource poor African countries (Bloland et al.

2000; Sowunmi 2002; Bloland 2003; Gasasira et al. 2003).

In the current study, the combination of artesunate plus

amodiaquine was therapeutically superior to chloroquine

plus pyrimethamine-sulfadoxine, the individual compo-

nents of which are readily and widely available in Africa.

The relatively accelerated and sustained clearance of

parasitaemia by artesunate plus amodiaquine produced a

large parasite reduction ratio on day 2 and a cure rate of

100% at day 28 of follow up. These findings are similar to

those reported from other African countries (Adjuik et al.

2002). A similar proportion of patients allocated to each

treatment regimen received paracetamol during the first

36 h of the study. Therefore it would appear that the

similar fever clearance despite inferior efficacy of chlo-

roquine plus pyrimethamine-sulfadoxine at clearing para-

sitaemia may be due to the enhanced antipyretic effect of

chloroquine in the combination (Hugosson et al. 2003).

Recent studies from Nigeria showed that the combina-

tion of chloroquine plus pyrimethamine-sulfadoxine is

therapeutically superior to chloroquine or pyrimethamine-

sulfadoxine alone and the combination is effective in the

treatment of uncomplicated malaria infection, producing a

cure rate of 98–100% on day 14 (Sowunmi 2002; Pitmang

et al. 2005). However, when the findings of the current

study are compared with a previous study in children from

Ibadan, there appears to be significant decline in the

therapeutic efficacy of chloroquine plus pyrimethamine-

sulfadoxine: in 2002, the cure rate with the combination

was 100% on day 28 (Sowunmi 2002) and 90% in the

current study. This decline could be attributable to

increasing resistance in the parasite population to mono-

therapy with chloroquine or pyrimethamine-sulfadoxine.

However, despite increasing resistance to chloroquine

monotherapy, resistance to amodiaquine monotherapy

appears to be low in this endemic area (Sowunmi 2002).

The sensitivity of P. falciparum to the combination of

chloroquine plus pyrimethamine-sulfadoxine varies in

Africa and elsewhere. While sensitivity appears encour-

aging in many areas of West Africa (Bojang et al. 1998;

Sowunmi 2002; Pitmang et al. 2005), and at day 14

following treatment in many areas of East Africa (Gasasira

et al. 2003; Talisuna et al. 2004), this is not so in the east

on day 28 and elsewhere (Schwobel et al. 2003; Talisuna

et al. 2004).

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ª 2005 Blackwell Publishing Ltd 1167

All of the chloroquine plus pyrimethamine-sulfadoxine

treatment failures were cured of their infections when they

were re-treated with artesunate plus amodiaquine. Overall,

this indicates a beneficial effect of the combination in

multidrug-resistant infections in children from this endemic

area.

The drug combinations used were well tolerated. The

reported adverse reactions were itching, presumably due to

the 4-aminoquinoline components of the combinations,

macular eruptions, in a 3-year-old child, presumably due to

the sulfadoxine component of pyrimethamine-sulfadoxine;

and gastrointestinal symptoms. The other reported symp-

toms, for example, those of gastrointestinal origin, were

not indistinguishable from the symptoms of malaria. Both

the sulfadoxine component of pyrimethamine-sulfadoxine,

and rarely, chloroquine (Cooper & Bunn 1991) can induce

haemolysis in Glucose 6 Phosphate Dehydrogenase

(G6PD)-deficient subjects, but no child, following treat-

ment, reported features suggestive of drug-induced hae-

molytic anaemia. Amodiaqune may induce leukopenia or

agranulocytosis when used repeatedly (or prophylactically)

(Hatton et al. 1986). In many endemic areas many people

with imagined malaria self-medicate with antimalarials

with a regularity that borders on prophylaxis (Sowunmi &

Salako 1992). Under this circumstance, the amodiaquine

component of artesunate amodiaquine combination can be

expected to induce leukopenia or agranulocytosis. There-

fore caution is required with the use of this combination in

many endemic areas.

Overall, a significantly higher proportion of children

treated with chloroquine plus pyrimethamine-sulfadoxine

carried gametocytes at least once during follow-up

compared with those treated with artesunate plus amo-

diaquine. Pyrimethamine-sulfadoxine monotherapy may

enhance gametocyte release into peripheral circulation

following treatment of malaria (Puta & Manyando 1997;

von Seidlein et al. 2001a; Sowunmi & Fateye 2003;

Sowunmi et al. 2004b). However, as shown in the present

study, it would appear the gametocyte releasing effect is

considerably reduced when the drug is used in combination

with 4-aminoquinolines (Sowunmi 2002; Sowunmi &

Fateye 2003) or as in other studies, with artesunate (von

Seidlein et al. 2001a,b). In other settings, after significant

resistance has developed to pyrimethamine-sulfadoxine

monotherapy, the gametocyte releasing effect may not be

modified by its combination with chloroquine (Tjitra et al.

2002).

Gametocyte carriage often peaks in children treated with

antimalarial monotherapy (for example, chloroquine or

pyrimethamine-sulfadoxine by day 7 following treatment

(Robert et al. 2000; Sowunmi et al. 2004b). In the

present cohort of children, gametocyte carriage following

treatment with artesunate plus amodiaquine was not seen

in children who did not carry gametocytes at enrolment.

Although artemisinin derivatives may be gametocytocidal,

the rapid clearance of asexual parasites by these drugs may

have prevented the progression of committed asexual

parasites to gametocytes in our cohort of children. The

latter is buttressed by the fact that delay in parasite

clearance greater than 2 days is associated with significant

risk of gametocyte carriage in children from this endemic

area (Sowunmi et al. 2004b). In other settings, for exam-

ple, in The Gambia and Thailand, artemisinin-based

combinations have significantly reduced gametocyte car-

riage (von Seidlein et al. 2001a,b) or reduced their infec-

tiousness to mosquitoes (Targett et al. 2001; Drakeley

et al. 2003) and may possibly interrupt transmission in

areas of low endemicity (Price et al. 1996).

Except in resource poor communities, there are few

justifications for the treatment of acute falciparum infec-

tions with chloroquine plus pyrimethamine-sulfadoxine in

Nigeria. First, the efficacy of the individual components of

the combination has declined significantly within the last

2 years; the prevalence of chloroquine and pyrimethamine-

sulfadoxine resistance is currently 50% and 25%,

respectively in under 5-year olds (Sowunmi et al. unpub-

lished). Second, and more importantly, when compared

with its efficacy 2 years ago, there has been a significant

decline in the efficacy of this combination in our area of

study. This decline in efficacy is confirmed by the finding

that comparison of the variant alleles in pre- and post-

treatment samples of the treatment failures indicates

genuinely recrudescent disease.

There are implications for using artesunate-amodiaquine

combination in Nigeria. In order to prolong the clinical life

of this potentially useful combination, it is essential to

discourage the availability and use of the individual

components as monotherapy. The individual components

are now readily available in many communities. In addi-

tion, it is necessary to completely withdraw chloroquine for

the treatment of malaria. The latter is crucial since the

mutations in Pfcrt genes conferring resistance to chloro-

quine also confer resistance to amodiaquine (Ochong

et al. 2003). Indeed, Happi et al (unpublished data) have

shown that these mutations, in Nigerian isolates of

P. falciparum, also confer resistance to amodiaquine. The

use of artesunate alone may also encourage the develop-

ment, in Nigerian isolates of P. falciparum, of resistance to

the combination since a minority of these isolates show

reduced susceptibility to artemisinin, the parent drug from

which artesunate is derived (Oduola et al. 1992).

There are policy implications of the findings of this

study. Although there are effective alternatives to the two

combinations evaluated, for example, coartemether or

Tropical Medicine and International Health volume 10 no 11 pp 1161–1170 november 2005

A. Sowunmi et al. Artesunate-amodiaquine for uncomplicated malaria

1168 ª 2005 Blackwell Publishing Ltd

pyrimethamine-sulfadoxine plus artesunate, these have not

been extensively evaluated in Nigeria. There are also cost

implications of using expensive combinations in resource-

poor communities, particularly in situations where the

diagnosis of malaria may be entirely presumptive.

Acknowledgements

The study received financial support from Ipca Pharma-

ceuticals Nigeria Plc. We are grateful to our clinic medical

officer Dr Olayiwola and clinic nurse Moji Amao for

assistance with running the study.

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Authors

A. Sowunmi (corresponding author), F. A. Fehintola, A. A. Adedeji, G. O. Gbotosho, E. Tambo, B. A. Fateye, T. C. Happi

and A. M. J. Oduola, Department of Clinical Pharmacology, University College Hospital, Ibadan, Nigeria.

Tel.: +234-2-2412101, Fax: +234-2-2411843; E-mail: malaria.iba@alpha.linkserve.com, akinsowunmi@hotmail.com

Tropical Medicine and International Health volume 10 no 11 pp 1161–1170 november 2005

A. Sowunmi et al. Artesunate-amodiaquine for uncomplicated malaria

1170 ª 2005 Blackwell Publishing Ltd