Author(s): Dr Anes Yang, Clinical Researcher, Department of Dermatology, St George Hospital, University of New South Wales, Sydney, New South Wales, Australia. Dr Monisha Gupta, Consultant Dermatologist, Department of Dermatology, Liverpool Hospital, University of New South Wales, Sydney, New South Wales, Australia. DermNet NZ Editor in Chief, A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. January 2018.
Antimalarial medications are drugs with immunomodulatory and anti-inflammatory effects. They are used to treat various skin conditions.
Antimalarial medications used in dermatology
Hydroxychloroquine has largely replaced quinacrine and chloroquine due to its better safety profile.
How do antimalarial medications work?
Antimalarials reduce cytokine production and the inflammatory response within macrophages, dendritic cells and lymphocytes where they are trapped within cytoplasmic lysosomes .
Anti-proliferative and immunomodulatory effects are mediated by:
Chloroquine and hydroxychloroquine are chemically similar and are part of the amino-quinoline family.
There is no cross-reactivity between the 4-amino-quinolines and quinacrine due to differences in chemical structure, therefore an adverse reaction to an amino-quinoline does not preclude the use of quinacrine.
Antimalarials are first-line medications for:
They are used second-line to treat:
Antimalarials are sometimes used to treat many other inflammatory skin conditions.
Antimalarials should not be used in patients with known hypersensitivity to the drug or pre-existing retinopathy. Care should be taken with children, the elderly, in pregnant and lactating women, and in patients with severe renal impairment.
Smoking has been reported to inhibit the P450 enzyme system, decreasing the efficacy of antimalarial therapy, especially in patients on chloroquine . Patients on antimalarial medications are advised not to smoke.
Hydroxychloroquine levels can be measured in the blood.
With the exception of severe retinopathy, adverse effects from antimalarials usually resolve when they are discontinued.
Chloroquine, and hydroxychloroquine to a lesser extent, can cause irreversible retinal toxicity. The cause is thought to be high affinity for melanin-containing cells in the retinal pigment epithelium (RPE) . The risk of toxicity is dependent on several factors.
Major risk factors for retinal toxicity
Routine screening is important because early antimalarial retinopathy does not cause symptoms.
Damage patterns vary with ethnicity
Antimalarials can cause transient or persisting nausea, flatulence, vomiting or diarrhoea that resolves with reduction or cessation of medication. Symptoms can be minimised by taking the medication with food.
Neuropsychological side effects due to antimalarial medications are rare, and usually occur in patients treated at higher doses than those used in dermatology. Psychosis, irritability, depression, insomnia and nightmares have been reported. Anti malarial medications have rarely been known to induce seizure in predisposed individuals.
Hematological side effects are uncommon. Haemolysis in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency, aplastic anaemia, and leukopenia has been reported but is rare . Screening for G6PD deficiency is not routinely recommended for hydroxychloroquine, but is required for chloroquine.
Anti-malarial medications can cause several interactions with other medications.
Increased plasma levels of:
Synergistic antiarrhythmic effects with chloroquine:
Decreased bioavailability of:
Increased bioavailability of antimalarial agent:
Decreased bioavailability of antimalarial agent:
Increased risk of myopathy:
Decreased effect of:
Antimalarial medications cross the placenta, and are considered Category D in pregnancy. This implies that they should only be taken during pregnancy if benefits outweigh the risks. However:
Chloroquine can cause fetal retinopathy and should not be used in pregnancy .
Hence, hydroxychloroquine is the safer option for women planning pregnancy or breast feeding.
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