Drug Interactions

Hydroxychloroquine has a narrow therapeutic window, slow elimination and variable pharmacokinetics leading to delayed actions and unpredictable clinical responses¹. As hydroxychloroquine is used in the treatment of chronic diseases such as rheumatoid arthritis and systemic lupus, it is often taken long term and in combination with other drugs². The most commonly prescribed drug classes with known interactions are:

• Antidiabetics³

• Selective serotonin/norepinephrine reuptake inhibitors (SSRIs/SNRIs)³

• Antipsychotics (typical and atypical)³

• Antiarrhythmics³

• Antibiotics²

• NSAIDs²

These drugs are prescribed extensively and are often administered in non-essential situations, resulting in a lack of caution about the use of these drugs². A possible hypothesis for the interaction of these drugs with hydroxychloroquine is through the activity of the CYP450 enzyme².

The most serious interaction is the increased risk of QT prolongation³. Less severe but more common interactions include hypoglycaemia, lowering of the convulsion threshold consequently increasing the risk of convulsions and the impairment of antiepileptic drugs⁴. However the risks associated with the use of hydroxychloroquine are more likely to occur in older adults with polypharmacy, especially in cases of co-administration with additional medication known to cause QT prolongation and for those with underlying cardiac conditions³.

References:

1. Velasco-González V, Fernández-Araque A, Sainz-Gil M, Jimeno N, Martín LH, Verde Z. Hydroxychloroquine and potential drug interactions in older adults. Archivos de bronconeumologia. 2020; 56(10): 679.

2. Choi BJ, Koo Y, Kim TY, Chung WY, Jung YJ, Park JE, et al. Risk of QT prolongation through drug interactions between hydroxychloroquine and concomitant drugs prescribed in real world practice. Scientific reports. 2021;11(1):1-10.

3. Ross SB, Wilson MG, Papillon‐Ferland L, Elsayed S, Wu PE, Battu K, et al. COVID‐SAFER: Deprescribing Guidance for Hydroxychloroquine Drug Interactions in Older Adults. Journal of the American Geriatrics Society. 2020;68(8):1636-46.

4. Hache G, Rolain J, Gautret P, Deharo C, Brouqui P, Raoult D. Combination of hydroxychloroquine plus azithromycin as potential treatment for COVID 19 patients: pharmacology, safety profile, drug interactions and management of toxicity. Preprint. 2020;22.