It may surprise you to learn that anti-malarial drugs are used by dermatologists and rheumatologists. But not to treat malaria! Chloroquine and hydroxychloroquine
(commonly known by its old brand-name Plaquenil) were first used to treat malaria, but the malaria-causing organism soon became resistant to them. However, during the treatment of patients with malaria who also had lupus, it was noted that their skin rashes improved. After these drugs were abandoned for the treatment of malaria, more study was done, and they were found to be effective for discoid lupus, subacute cutaneous lupus, dermatomyositis, rheumatoid arthritis, and psoriatic arthritis.
Plaquenil has a better safety profile than chloroquine and is most commonly used today. When the drugs were first used, the dosages were generally higher than prescribed today, and a peculiar side-effect on the retina of the eye occurred that permanently affected vision. The recommended dose was subsequently lowered based on the patient’s weight which helps to prevent retinopathy over time. We also request a detailed baseline eye exam which includes color vision and visual field-testing, and repeated every 6-12 months to detect the earliest changes in the retina which may be reversible by stopping or reducing the dose of Plaquenil. Although we screen for them, Plaquenil rarely has any effect on blood counts, kidney or liver function. It can also be combined with other medicines including prednisone and methotrexate that may be needed to treat the conditions mentioned above. Abdominal symptoms such as cramps, constipation, or diarrhea may occur during the first few weeks, but they are usually mild, well-tolerated, and eventually resolve spontaneously. I usually start with a low dose of 100-200 mg per day to help the patient adapt to the medicine and allow an increase in dose later to as high as 300-400 mg per day.
Less common adverse effects of Plaquenil are drug-induced skin rashes. These rashes may consist of many small red bumps or bright red skin covering most of the body. The severity of the rash indicates to the clinician whether the drug needs to be stopped and even whether it will be tried again. Some patients, particularly those with a history of psoriasis or psoriatic arthritis, have been reported to develop flaring of their pre-existing psoriasis or the new appearance of typical dry scaling psoriasis or a pustular psoriasis variant. The medical literature is very confusing on this issue. The incidence of new-onset or flaring psoriasis associated with Plaquenil varies from 0-100% depending on which case series report you read!
Allergic and psoriasis-like rashes tend to develop within the first few weeks or months of starting Plaquenil. If Plaquenil helps a serious chronic disease such as lupus, it may be taken for years. Some of these long-term users will develop grayish-blue pigmentation on
their shins and forearms. The discoloration is now considered to be more likely to occur in thin skin that gets easily traumatized, especially if superficial bleeding occurred in the bruises. This pigmentation gradually fades over many months’ time if the dose of Plaquenil is reduced or stopped.
Plaquenil is notoriously a slow-acting drug. A therapeutic level in the blood, skin, and joints may take up to 3 months to achieve, therefore, the patient must be treated for at least 3 months and preferably 6 months before a decision regarding effectiveness can be made. The mechanism of action is thought to be anti-inflammatory, but Plaquenil also seems to reduce sensitivity to sunlight. It has also been noted recently that smoking reduces the effectiveness of Plaquenil in treating lupus, thus, smoking cessation should be instituted in all patients taking Plaquenil.