From the FDA Drug Label
A half-life of 123. 5 days in plasma were observed following a single 200 mg oral hydroxychloroquine sulfate dose to healthy male volunteers. Following chronic oral administration of hydroxychloroquine, the absorption half-life was approximately 3 to 4 hours and the terminal half-life ranged from 40 to 50 days
The half-life of hydroxychloroquine is 123.5 days in plasma after a single dose, and the terminal half-life ranges from 40 to 50 days after chronic oral administration 1.
From the Research
The half-life of hydroxychloroquine is approximately 40-60 days, as reported in the most relevant study 2. This extremely long half-life means that the drug takes a significant amount of time to reach steady-state concentrations in the body and also requires a long period to be eliminated after discontinuation. Hydroxychloroquine's extended half-life is due to its extensive tissue binding, particularly in melanin-containing tissues, liver, kidneys, and lungs, which act as reservoirs for the drug. This pharmacokinetic property explains why hydroxychloroquine requires loading doses when initiating therapy for conditions like rheumatoid arthritis or lupus, and why its therapeutic effects may not be apparent for weeks to months. It also explains why the drug's beneficial effects continue for some time after discontinuation and why adverse effects, particularly retinopathy, may progress even after stopping the medication. The long half-life necessitates careful monitoring during long-term use, as also suggested by other studies 3, 4. Some studies have also highlighted the importance of considering the half-life of hydroxychloroquine when discontinuing the drug, as its effects can persist for several days after stopping 5. Key points to consider include:
- The half-life of hydroxychloroquine is approximately 40-60 days
- The drug requires loading doses due to its extensive tissue binding
- Therapeutic effects may not be apparent for weeks to months
- Adverse effects can progress even after stopping the medication
- Careful monitoring is necessary during long-term use.