Background Chloroquine and hydroxychloroquine are drugs widely used in the treatment of systemic lupus erythematosus (SLE).
Objectives The aim of our study was to assess the toxicity of antimalarials in the treatment of SLE Portuguese patients.
Methods 234 outpatients satisfying the 1982 revised ARA criteria for SLE and regularly followed in our Rheumatology Unit were evaluated. 222 (94,9%) were females and 12 (5,1%) were males. The mean age of SLE onset was 30,1 years. The mean duration of follow-up was 5,5 years.
Results 157 (67,1%) patients were medicated with antimalarials, 59 (37,6%) with chloroquine in a daily dose of 3–5 mg/kg and 98 (62,4%) with hydroxychloroquine in a daily dose of 5–7 mg/kg. 77 (32,9%) patients were never treated with chloroquine or hydroxychloroquine. In the chloroquine group, 28 (47,5%) patients were still on therapy and in 31 (52,5%) patients the chloroquine was stopped. In the hydroxychloroquine group 64 (65,3%) patients remain on therapy and in 34 (34,7%) patients the drug was suspended. The reasons to stop chloroquine were ocular toxicity in 20 (64,5%) patients, gastrointestinal intolerance in 5 (16,1%), cutaneous rash in 2 (6,4%), patient will in 2 (6,4%) and medical advice but without adverse effects in 2 (6,4%). The reasons to suspend hydroxychloroquine were ocular toxicity in 15 (44,1%) patients, patient will in 6 (17,6%), cutaneous rash in 3 (8,8%), medical advice but without adverse effects in 3 (8,8%), pregnancy in 3 (8,8%), death not related with the antimalarial in 2 (5,9%), headache and dizziness in 1 (2,9%), gastrointestinal intolerance in 1 (2,9%).
Conclusion In our patients the antimalarial discontinuation was frequent and occurred in 65 (41,4%) out of the 157 treated patients. It occurred more often in the chloroquine group (52,5%) as compared to the hydroxychloroquine (34,7%) group. Most of the adverse effects reported were mild. Ocular toxicity was the most frequent adverse effect implicated in the drug discontinuation and it was reported in 35 (22,3%) of the 157 treated patients. Chloroquine induced more ocular toxicity as compared to hydroxychloroquine (64,5% vs 44,1%). Most of the patients that have stopped the drug because of the abnormalities detected in the ophthalmologic evaluation had no clinical symptoms. There were no blindness reports. The great number of ocular toxicity cases detected could be the result of the use of high sensitive tools in the ophthalmologic evaluation such as computerised evoked potentials or fluoresceinic angiography. In addition, other factors such as sun exposure and low body mass might have contributed to a higher rate of ocular toxicity as compared to Northern European reports. In the 157 patients group there were no reports of muscle, neurological, liver, renal or haematological abnormalities due to the antimalarial therapy.
The antimalarials are useful and relatively safe drugs in the treatment of SLE. Hydroxychloroquine seems to be less toxic than chloroquine. The need of a periodic ophthalmologic evaluation once or twice yearly was supported by our study.