...if taking high doses daily >500mg, you may want to get your liver function checked every year - 6 months
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FYI all those studies about liver difficulties were about fake niacin - not nicotinamide.
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No, some of the studies were conducted with niacin in different formulations. It is in the label for niacin. A drug manufacturer would avoid this verbiage if possible...
Liver Dysfunction
Cases of severe hepatic toxicity, including fulminant hepatic necrosis, have occurred in patients who have substituted sustained-release (modified-release, timed-release) Niacin products for immediate-release (crystalline) Niacin at equivalent doses.
Niacin extended-release tablets should be used with caution in patients who consume substantial quantities of alcohol and/or have a past history of liver disease. Active liver diseases or unexplained transaminase elevations are contraindications to the use of Niacin extended-release tablets.
Niacin preparations have been associated with abnormal liver tests. In three placebo-controlled clinical trials involving titration to final daily Niacin doses ranging from 500 to 3,000 mg, 245 patients received Niacin for a mean duration of 17 weeks. No patient with normal serum transaminase levels (AST, ALT) at baseline experienced elevations to more than 3 times the upper limit of normal (ULN) during treatment with Niacin. In these studies, fewer than 1% (2/245) of Niacin patients discontinued due to transaminase elevations greater than 2 times the ULN.
Liver-related tests should be performed on all patients during therapy with Niacin. Serum transaminase levels, including AST and ALT (SGOT and SGPT), should be monitored before treatment begins, every 6 to 12 weeks for the first year, and periodically thereafter (e.g., at approximately 6-month intervals). Special attention should be paid to patients who develop elevated serum transaminase levels, and in these patients, measurements should be repeated promptly and then performed more frequently. If the transaminase levels show evidence of progression, particularly if they rise to 3 times ULN and are persistent, or if they are associated with symptoms of nausea, fever, and/or malaise, the drug should be discontinued.
https://www.drugs.com/pro/niacin.html
https://www.accessdata.fda.gov/drugsatfda_docs/label/2015/020381Orig1s051lbl.pdf
https://dailymed.nlm.nih.gov/dailymed/getFile.cfm?setid=92b3ec1d-0dc7-4bde-9817-57b1bdf7f0b9&name=NIACIN
Note data used in licensure (prescribing information) may not be available in the general medical literature and could be held ‘on file’.
That ain't nicotinamide. There is only one real niacin. Extended release is NOT nicotinamide.