Low-dose Naltrexone: Safety and precautions - CancerChoices

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.

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—0.25mg is a good starting point. 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. Although a large 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, this rate was lower than adverse events with placebos, with a weak trend for significance. The researchers conclude “Naltrexone does not appear to increase the risk of serious adverse events over placebo. These findings confirm the safety of oral naltrexone when used in licensed indications.”1Bolton 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:2Elsegood 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.

  • Occasionally, during the first week of use, some may complain of 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 (very infrequent and limited to people with liver failure)
  • Reductions in renal function (extremely rare)

Most side effects reported by patients can often be prevented by starting at a low dosage and increasing by 1 mg per week until reaching 4.5 mg;3Elsegood L. Ed. The LDN Book. Vermont: Chelsea Green Publishing. 2016. p. 21. reviewer’s note: in clinical practice very sensitive patients are sometimes started at a dose of 0.25mg per week and titrated to their goal dose, which may be between 1.5-4.5mg per day

Do not use (contraindications)

Warnings from Low Dose Naltrexone:4Bihari 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. Patients who have become dependent on daily use of opioid-containing 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. Then after surgery, should opioid-based medications be used for pain management, LDN should not be restarted until the patient is given permission by their physician to restart.

Full-dose naltrexone (50 mg) carries a cautionary warning against its use in those with liver disease. This warning was placed because of adverse liver effects that were found in experiments involving 300 mg daily. The 50 mg dose and the much smaller 3.0 mg and 4.5 mg doses apparently do not impair liver function, except in people with liver failure.

People who have received organ transplants and who therefore are taking immunosuppressivepartially or completely suppressing the immune response medication permanently are cautioned against the use of LDN because it may counter the effect of those medications, which could be potentially lethal.

Keep reading about low-dose naltrexone


Nancy Hepp, MS

Lead Researcher
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Ms. Hepp is a researcher and communicator who has been writing and editing educational content on varied health topics for more than 20 years. She serves as lead researcher and writer for CancerChoices and also served as the first program manager. Her graduate work in research and cognitive psychology, her master’s degree in instructional design, and her certificate in web design have all guided her in writing and presenting information for a wide variety of audiences and uses. Nancy’s service as faculty development coordinator in the Department of Family Medicine at Wright State University also provided experience in medical research, plus insights into medical education and medical care from the professional’s perspective.

Nancy Hepp, MS Lead Researcher


Laura Pole, MSN, RN, OCNS

Senior Clinical Consultant
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Laura Pole is senior clinical consultant for CancerChoices. Laura is an oncology clinical nurse specialist who has been providing integrative oncology clinical care, navigation, consultation, and education services for over 40 years. She is the co-creator and co-coordinator of the Integrative Oncology Navigation Training at Smith Center for Healing and the Arts in Washington, DC. Laura also manages the “Media Watch Cancer News That You Can Use” listserv for Smith Center/Commonweal. In her role as a palliative care educator and consultant, Laura has served as statewide Respecting Choices Faculty for the Virginia POST (Physician Orders for Scope of Treatment) Collaborative as well as provided statewide professional education on palliative and end-of-life care for the Virginia Association for Hospices and Palliative Care.

For CancerChoices, Laura curates content and research, networks with clinical and organizational partners, brings awareness and education of integrative oncology at professional and patient conferences and programs, and translates research into information relevant to the patient experience as well as clinical practice.

Laura sees her work with CancerChoices as a perfect alignment of all her passions, knowledge and skills in integrative oncology care. She is honored to serve you.

Laura Pole, MSN, RN, OCNS Senior Clinical Consultant

Dan Rubin, ND, FABNO

Naturopathic oncologist
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Dan Rubin, ND, FABNO, is a board certified naturopathic oncologist practicing in both Scottsdale and Flagstaff, Arizona. Dr. Rubin is the founding president of the Oncology Association of Naturopathic Physicians (OncANP) and has been a long-time member of the Arizona Naturopathic Physicians Medical Board. He is the co-founder of Naturopathic Specialists, LLC, with his wife, Debi Smolinski, ND. Dr. Rubin focuses on naturopathic and integrative approaches to people with cancer, treating both children and adults. He enjoys trail running in the Sonoran desert near his house.

Dan Rubin, ND, FABNO Naturopathic oncologist

Last update: December 12, 2023

Last full literature review: September 2021

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