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.
Doxycycline
Doxycycline Hyclate / Monohydrate
Brand names: Vibramycin, Oracea, Doryx
ORIGINALLY APPROVED FOR
Bacterial Infections (acne, Lyme disease, respiratory infections)
Doxycycline targets cancer stem cells (CSCs) via a unique mechanism: it inhibits mitochondrial biogenesis and function. Cancer stem cells depend heavily on oxidative phosphorylation (OXPHOS) in their mitochondria, unlike bulk tumour cells which prefer glycolysis. By inhibiting mitochondrial ribosome protein synthesis, doxycycline selectively starves CSCs of energy. It also inhibits matrix metalloproteinases (MMPs) — key enzymes in tumour invasion and metastasis.
Molecular Pathways Targeted
Mechanism of Action in Cancer
Inhibits mitochondrial 30S ribosomal subunit → blocks mitochondrial protein synthesis → impairs OXPHOS in cancer stem cells → energy starvation and cell death. Also inhibits MMPs-2, 9, 13 (reduces invasion and metastasis) and suppresses NF-κB and Akt survival signalling.
Cancers Studied
Typical Off-Label Dosing
100–200 mg daily (standard antibiotic dosing). Some protocols use 100 mg twice daily. Take with food and upright position for 30 min to prevent oesophageal irritation. Sun protection important (photosensitivity).
* Dosing information from research literature only. Not a prescription. Requires physician supervision.
Cautions & Drug Interactions
- Photosensitivity — use high-SPF sun protection
- Oesophageal irritation — take with full glass of water, remain upright 30 min
- May disrupt gut microbiome — probiotic supplementation recommended
- Reduced absorption with dairy products, antacids, iron supplements — take 2h apart
- Avoid in pregnancy and children under 8 (dental staining, bone effects)
- Long-term antibiotic resistance concern — periodic breaks sometimes used