Study on Hydroxychloroquine vs chloroquine

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The Efficacy/Toxicity Trade-off for Long-term Use of Chloroquine and

Hydroxychloroquine in Rheumatic Diseases

Paper: Long term effectiveness of antimalarial

drugs in rheumatic

diseases.

Authors: Aviria-Zubieta JA, Galindo- G,

Newman S, et al.

Ref: ls of Rheumatic Diseases 1998;57:582-587.

Type: Epidemiology Study

Summary: Antimalarial drugs, such as

chloroquine and

hydroxychloroquine, are commonly used to treat

various

rheumatic diseases, including rheumatoid

arthritis (RA),

systemic lupus erythematosus (SLE),

palindromic arthritis

(PA) and psoriatic arthritis. Most previous

studies of the

long-term effectiveness of these drugs

considered them as a

group, whereas this retrospective, cohort

study examined

potential differences between chloroquine and

hydroxychloroquine. The medical records of 940

patients

treated with antimalarial drugs for various

rheumatic

disorders provided sufficient information for

inclusion in the

study. The main outcome measures were the

cause and time

of treatment discontinuation. Causes for

discontinuation were

categorized as 'inefficacy', 'toxicity',

'other' or 'uncertain.'

The cohort comprised patients with RA (59%),

SLE (19%),

PA (14%) and other nonspecified disorders

(8%).

Chloroquine and hydroxychloroquine

respectively accounted

for 58% and 42% of the antimalarial

prescriptions. These

drugs were the first choice, second line

treatment in 72% of

patients. One half of the cohort had

discontinued treatment

when the data were collected because of

inefficacy (19%),

toxicity (15%) or other reasons (16%).

Kaplan-Meier

survival curve analysis showed that

discontinuations because

of inefficacy were significantly lower in

patients treated with

chloroquine compared with those on

hydroxychloroquine

from about 1 year onward (p = 0.009). However,

there was

a trend for more patients to discontinue

chloroquine because

of toxicity. Other analyses examined the

associations of

different variables with the outcome of

treatment. For all

causes of discontinuation, the type of

antimalarial drug was

not a significant predictor. The type of drug

was, however,

the best predictor for discontinuation because

of toxicity and

there was less chance of discontinuation from

hydroxychloroquine than chloroquine for this

reason [hazard

ratio (HR) = 0.62; 95% confidence intervals

(CI) 0.4-0.96].

Type of drug was also a significant predictor

of

discontinuation because of inefficacy and

there was a greater

chance of discontinuing hydroxychloroquine

because of this

(HR = 1.4; 95% CI 1.06-1.96).

Assessment of side effects showed that the

incidence in

patients on chloroquine was almost twice that

in patients on

hydroxychloroquine (28% versus 15%; p <

0.00001). Of

these patients, 81% and 64% discontinued

treatment,

respectively (p < 0.01). The overall side

effect profile of

hydroxychloroquine was more favorable than

that of

chloroquine. One case of retinal toxicity was

considered to

be probably related to chloroquine.

Overall discontinuation rates were found to be

similar for

chloroquine and hydroxychloroquine in this

study. Although

the long-term effectiveness of these drugs

can, therefore, be

considered similar, drug selection will be

influenced by

differences in their efficacy and toxicity

(and possibly costs).