This information is for educational purposes only. Off-label drug use carries risks. Always consult a qualified physician before using any drug outside its approved indication.
Hydroxychloroquine
Hydroxychloroquine Sulphate
Brand names: Plaquenil
ORIGINALLY APPROVED FOR
Malaria, Rheumatoid Arthritis, Lupus
Hydroxychloroquine (HCQ) inhibits autophagy — the process cancer cells use to recycle damaged components and survive under stress (including chemotherapy stress). By raising lysosomal pH, HCQ prevents the final step of autophagy (autolysosome degradation), trapping cancer cells in a pro-death state. It is being extensively tested as a chemotherapy sensitiser — multiple Phase I/II trials show it enhances the efficacy of various cytotoxic agents.
Molecular Pathways Targeted
Mechanism of Action in Cancer
Accumulates in lysosomes → raises lysosomal pH → blocks acid-dependent hydrolytic enzymes → prevents autolysosome degradation → autophagy blockade → cancer cell stress and death. Synergises with many chemotherapies by preventing cancer cell 'escape' via autophagy recycling.
Cancers Studied
Typical Off-Label Dosing
200–400 mg daily (same as standard autoimmune dosing). Must not exceed 5 mg/kg body weight/day to avoid retinal toxicity. Requires baseline and annual ophthalmology monitoring. Typically used as combination adjunct with chemotherapy.
* Dosing information from research literature only. Not a prescription. Requires physician supervision.
Cautions & Drug Interactions
- Retinal toxicity with long-term use — mandatory baseline and annual eye exams
- QT prolongation — ECG monitoring recommended, avoid with other QT-prolonging drugs
- Hypoglycaemia — monitor blood sugar
- Muscle weakness and neuropathy with long-term use
- Contraindicated in G6PD deficiency
- Evidence as monotherapy is weak — best studied as combination with conventional treatment