This prescription drug is used off-label in low doses to treat people with cancer, with notable but very preliminary successes in cases where the cancers were difficult-to-treat or quite advanced.
Safety and precautions
Naltrexone is generally safe. However, its effect on cancer is not straightforward: while many preclinical (animal or lab) studies suggest that naltrexone could help fight cancer, animals treated with naltrexone developed more aggressive cancer in at least two studies.1Kuramochi T, Sano M et al. Effects of tramadol via a µ-opioid receptor on pancreatic ductal adenocarcinoma in vitro and in vivo. Regional Anesthesia and Pain Medicine. 2024 Mar 4;49(3):200-208; Szymaszkiewicz A, Mierzejewski M et al. The role of bidirectional communication between the adipokines and the endogenous opioid system in an experimental mouse model of colitis-associated colorectal cancer. Pharmacology Reports. 2024 Feb;76(1):112-126.
Caution is needed among people taking thyroid hormone replacement for a diagnosis of Hashimoto’s thyroiditis with low thyroid function (hypothyroidism). LDN ought to begin at the lowest range. LDN may lead to a rapid decrease in the autoimmune disorder, which then may require a rapid reduction in your dose of thyroid hormone replacement in order to avoid symptoms of hyperthyroidism; see Expert commentary in How do experts use low-dose naltrexone? ›
Side effects or adverse events
Naltrexone appears to be at least as safe as a placebo treatment. A meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 89 studies found about 20 adverse events per 100 people, fewer adverse events than seen with people taking placebos.2Bolton M, Hodkinson A et al. Serious adverse events reported in placebo randomised controlled trials of oral naltrexone: a systematic review and meta-analysis. BMC Medicine. 2019 Jan 15;17(1):10.
Typical side effects include:3Elsegood L. Ed. The LDN Book. Vermont: Chelsea Green Publishing. 2016. p. 20; Bihari B. LDN and cancer. Low Dose Naltrexone. Feb 21, 2021. Viewed September 19, 2021.
- Difficulty sleeping, nightmares and vivid dreams
- Transitory stomach cramps and diarrhea
- Headache during the initial phase
- Agitation or dizziness, or involuntary movements (infrequent)
- Constipation and/or diarrhea: Infrequent, and more common among people with IBS, IBD, and/or Crohn’s disease
- Elevated liver enzymes
- Reductions in renal function (rare)
Side effects can often be prevented by starting at a low dosage and increasing by 1 mg per week until reaching 4.5 mg.4Elsegood L. Ed. The LDN Book. Vermont: Chelsea Green Publishing. 2016. p. 21.
Do not use (contraindications)
Warnings from Low Dose Naltrexone:5Bihari B. LDN and cancer. Low Dose Naltrexone. Feb 21, 2021. Viewed September 19, 2021.
Because LDN blocks opioid receptors throughout the body for three or four hours, people using opioid medication—Ultram/tramadol, morphine, dextromethorphan, Percocet/oxycodone, Duragesic/fentanyl patch, or codeine-containing medication—should not take LDN until the opioid medicine is completely out of their system. People who take daily opioid pain medication may require 10–14 days weeks of slowly weaning off opioids entirely (while first substituting full doses of non-opioid pain medications) before beginning LDN safely. But without question, use of naltrexone by anyone in this category should be discussed with their physician.
LDN users preparing for surgery generally discontinue LDN for one or two days prior to the surgery. After surgery, opioid-based medications are often used for pain management, so people should not restart LDN until cleared by their physician.
Full-dose naltrexone (50 mg) can cause liver problems among people with liver disease.
People who have received organ transplants and who therefore are taking immunosuppressivepartially or completely suppressing the immune response medication should not take LDN because it could counter the effect of those medications, which could be potentially lethal.
References