There are some members on this forum who are taking either mebendazole or fenbendazole, two antihelminthic drugs that appear to have anticancer activity. The former is for human use and the latter for animals. I did a web and literature search to obtain more information on these drugs - this post summarizes the information I found (and which I will update periodically). I hope members find it useful. I should mention that I have been following a modified COC Protocol since early December 2019 and substituted mebendazole for fenbendazole. I will know next week whether the protocol has affected the trajectory of the PSA.
Cheers,
Phil
Mebendazole and Fenbendazole (Interim Summary - 2020.02.07)
1. Mebendazole and fenbendazole have very low solubilities but publicly available solubility data is variable. Nevertheless, it is possible that fenbendazole may have a solubility that is ~10 fold lower than mebendazole and therefore likely achieves a lower systemic concentration, when compared as solids.
2. Fenbendazole formulations in the form of suspensions or dispersions likely increase the bioavailability of fenbendazole compared to solid formulations in powder form, because the particle size is very small and dispersants are used to stabilize the suspensions.
3. The additives used to prepare fenbendazole products, solid and suspensions, are typical of those used in human drug products. On the other hand, the purity or quality of those additives is unknown.
4. Mebendazole very likely achieves an effective systemic concentration considering that adverse reactions have been observed during clinical trails and the post marketing period.
5. Although mebendazole and fenbendazole have very low solubilities in solid form, high dosages and prolonged exposure to the antihelminthics should be avoided because of the potential for liver damage (e.g., jaundice, elevated liver enzymes (ALT, AST), agranulocytosis, neutropenia and immunosuppression.
6. Increasing the bioavailability of fenbendazole by untested and unproven methods is not recommended, due to the risk of serious side effects. Alternatively, cimetidine, an anti-acid drug, can be used as a safer method to improve the systemic concentration of the antihelminthic.
7. A weekly intermittent dosage schedule appears to be efficacious according to anecdotal reports, but continuous dosing for 1 to 3 months can be followed similar to the way clinical trials with mebendazole are being conducted (Clinical Trials.gov).
8. Interruptions in taking the antihelminthics should be based on changes in blood biomarkers, cancer specific antigens, circulating tumor cell load (if available) and progression according to CAT and bone scans.
9. Fenbendazole and mebendazole should not be used as substitutes for standard of care (SOC) therapies. They should be used as adjuvants to SOC providing that there is no known interference with the therapy.
10. It is advisable to closely monitor liver enzymes (ALT, AST, ALP) as well as lymphocytes when taking antihelminthics. It is further advised to start at a moderate dosage and to escalate the dosage after a period of time (1 – 4 weeks).
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