Hydroxychloroquine is an antimalarial drug commonly used in the therapy of rheumatoid arthritis and other diseases of the connective tissue. Since its discovery in 1955, it has found other numerous applications and occupies an important position in the dermatological treatment repertoire. Its toxicity and number of interactions with other preparations are relatively low, so it easily allows one to limit the use of glycocorticosteroids and consequently, inter alia, to reduce the number of secondary infection cases. The exact mechanism of action of this drug has not been fully explained yet, but numerous clinical observations and experimental studies have recorded its antithrombotic, hypoglycemic and hypolipidemic properties (1).

Alopecia cicatricans (fig. 1) is a rare disease characterized by a progressive course and permanent damage to hair follicles. Despite the unambiguous hyperactivity of the immune system, the etiology of the disease still raises many doubts. Due to a significant deterioration of the patients’ quality of life, lack of social acceptance as well as accompanying symptoms such as pruritus, the burning sensation and considerable hypersensitivity of the scalp, it is often necessary to initiate systemic treatment (2). Beside topically or systemically applied glycocorticosteroids, doctors are increasingly inclined to apply non-biological drugs modifying the course of the disease, which include hydroxychloroquine.

Hydroxychloroquine belongs to the group of antimalarial drugs. It is used to treat malaria, rheumatoid arthritis and lupus. It is also applied in dermatology due to its anti-inflammatory properties. Its mechanism of action has not been fully explained yet: it includes, inter alia, influence on lysosomes, phospholipase A2 inhibition, phagocytosis suppression, peroxide synthesis inhibition and intracellular pH increase. This results in a decreased activity of CD4 lymphocytes, inhibition of cytokine release from monocytes and inhibition of antibody production. Due to the observed affinity to pigments, including melanin, the drug may increase the risk of retinopathy development. Moreover, it is applied in cutaneous porphyria because it binds to porphyrins, facilitating their elimination with urine. Literature also mentions aldosterone concentration increase caused by hydroxychloroquine. Its bioavailability is nearly complete, but it should nonetheless be taken during meals to increase its absorption. It reaches the highest serum concentration after approx. 1-3 hours, binding to proteins in approx. 55%. In the case of rheumatoid diseases, the onset of its action may be observed as late as after approx. 4-6 months. It is metabolized mainly in the liver and eliminated mainly via the kidneys. One must exercise caution in pregnant women because the drug penetrates the placental barrier (3-6).

The appropriate dosage scheme does not depend on the patient’s actual weight because the preparation deposition in the fatty tissue is scant. It should not exceed 6.5 mg/kg of body weight for so-called ideal weight, even in patients with significant obesity. If the patient’s weight falls within the correct BMI range or is lower than that, the optimal dose of hydroxychloroquine is 5.0 mg/kg of body weight. In most descriptions of dermatological diseases and in the cases of good tolerance, a dose of 400 mg/day was applied. Clinical experience has shown that a bigger dose does not result in the expected improvement and increases the risk of retinopathy development instead. The pharmacokinetic properties of the drug allow one to apply alternative doses in order to optimize the daily dose. This means that one can apply a scheme consisting of alternating 200 mg/day and 400 mg/day doses in order to achieve a daily dose of 300 mg/day. If an adequate response does not follow, one can determine the blood level of hydroxychloroquine, which should equal 750 ng/ml at the initial stage and 500 ng/ml during the administration of the maintenance dose. Given the fact that full saturation with the preparation may take up to several months, one can consider an initial dose of 1,200 mg/day at the beginning of the therapy depending on the clinical situation. Unfortunately, gastric complaints make the abovementioned dosage scheme impossible to apply in most cases. The common view that assumes the influence of smoking on the hydroxychloroquine dosage scheme is rather unclear. Nevertheless, all patients should be educated about the harmful influence of nicotinism, especially if other immunosuppressive drugs are applied. Based on the current findings of experts, it is permissible to administer hydroxychloroquine to pregnant women despite the placental barrier penetration if the therapy brings noticeable results. Dosage modification is related to special clinical situations and aimed at reducing the risk of retinopathy, which is one of the most serious treatment complications. In patients with liver dysfunctions and elderly patients, the drug must be applied with caution because the two factors are characterized by impaired metabolism of the drug, even though they do not increase the risk of retinopathy. Hydroxychloroquine may cause hypoglycemia, which is a very important fact when treating patients who take antidiabetic drugs. In the event of recurring hypoglycemia episodes, the dosage scheme must be reviewed. Special caution must also be exercised when treating patients with kidney dysfunctions (the risk of retinopathy doubles) and women who take tamoxifen (the risk of retinopathy increases five times). Hydroxychloroquine should be avoided in patients with retina dysfunctions, blood picture disturbances, glucose-6-phosphate dehydrogenase deficiency as well as severe stomach and intestine disorders. One must remember that hydroxychloroquine may aggravate the course of psoriasis, porphyria and myasthenia (3-9).

Contrary to the common opinion about low toxicity of hydroxychloroquine and the small number of its interactions, one must remember that certain medicinal products constitute a serious threat, while others require particular caution (tab. 1).