I would issue a strong warning that high dose b12 is safe, and effective for treating some problems so no need to worry. Anecdotally I have taken cyana, and methyl b12 high dose with no problems.
https://www.ncbi.nlm.nih.gov/pubmed/25982504
BACKGROUND:
High-dose of methylcobalamin promotes nerve regeneration in rats with acrylamide neuropathy. A double-blind controlled trial suggested that high-dose methylcobalamin could increase compound muscle action potentials in patients with amyotrophic lateral sclerosis (ALS). A large-scale extended period human trial is now on-going in ALS (Clinicaltrial.gov
NCT00444613). We attempted to study whether high-dose methylcobalamin can improve symptoms or retard progression of motor dysfunction in the wobbler mouse model of ALS.
METHODS:
After initial diagnosis of the disease at the postnatal age of 3-4 weeks, wobbler mice received methylcobalamin (3 or 30 mg/kg, n=10/group) or vehicle (n=10), daily for 4 weeks by intraperitoneal administration in a blinded fashion. We compared clinical symptoms and pathological changes among all groups. Vitamin B12 concentrations were measured in the serum, the skeletal muscle and the spinal cord of three groups (n=5/group).
RESULTS:
In comparison with vehicle, mice treated with
ultra-high dose (30 mg/kg) of methylcobalaminsignificantly inhibited muscle weakness and contracture in the forelimb, and increased the weight of the bicep muscles and the number of musculocutaneous nerves. Methylcobalamin-treated mice significantly elevated vitamin B12 concentrations of the serum, the bicep muscle and the spinal cord compared to vehicle.
CONCLUSION:
Our results suggest that treatment with methylcobalamin could delay progression of motor symptoms and neuropathological changes in wobbler mouse motor neuron disease if very high doses are used.
https://www.ncbi.nlm.nih.gov/pubmed/17969354
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder affecting both upper and lower motor neurons. Weakness may begin in the legs, hands, proximal arms, or pharynx. The course is relentless and progressive without remissions, relapses, or even stable plateaus. There is no effective drug therapy for ALS, although riluzole has been shown to prolong life in sufferers, without tracheostomy. A vitamin B12 analog, methylcobalamin, has a protective effect on cultured cortical neurons against glutamate-induced cytotoxicity. We have shown the ultra-high-dose methylcobalamin (
25 mg/day i.m.) slows down the progressive reduction of the CMAP (compound muscle action potential) amplitudes in ALS in the short term (4 weeks). The latencies of SSR (sympathetic skin response) were shorter after treatment (
50 mg/day i.v., 2 weeks). In the long-term effect of methylcobalamin (50 mg/day i.m., twice a week),
the survival time (or the period to become respirator-bound) was significantly longer in the treated group than in the untreated. Larger-scale randomized double blind trial was started in Japan in order to evaluate the long-term efficacy and the safety of ultra-high-dose methylcobalamin for sporadic or familial cases of ALS.
