Narconon Proceedures are deadly: The Toxicity of Niacin

The Toxicity of Niacin

Reprinted from the April 1994 issue of Medical Sciences Bulletin, published by Pharmaceutical Information Associates, Ltd.

Niacin (nicotinic acid) is widely used for reducing serum cholesterol levels, in part because it is effective, and in part because it is available and cheap. In doses of 2 to 3 g daily, it reduces levels of total and high-density lipoprotein cholesterol (LDL-C) by an average of 20% to 30%, reduces triglyceride levels 35% to 55%, increases high-density lipoprotein cholesterol (HDL-C) 20% to 35%, and reduces Lp(a) lipoprotein. In primary prevention, niacin reduces total mortality as well as mortality from coronary artery disease; used in secondary prevention along with bile acid resins, it slows or reverses the progression of atherosclerosis. And it costs only about $2.00 for a 10-day supply. Does all this sound too good to be true? Results from a recent study by McKenney et al. (Medical College of Virginia School of Pharmacy) indicate that not all the news about niacin is good news. In therapeutic doses, niacin can be dangerous, particularly sustained-release niacin.

The Virginia researchers conducted a randomized, double-blind, parallel-group comparison of sustained-release (SR) and immediate-release (IR) niacin in 46 patients with hypercholesterolemia. The 36-week trial included a 6-week evaluation and instruction period followed by five 6-week treatment periods during which niacin was given in escalating doses (500 mg/day initially, increasing up to 3Êg/day). Both the IR niacin product (Rugby Laboratories, division of Marion Merrell Dow) and the SR niacin (Goldline Laboratories) were effective for improving the lipid profile. At the highest (3-g) dose, SR niacin reduced total cholesterol by about 40% and LDL-C by 50%, while IR niacin reduced total cholesterol by about 16% and LDL- C by about 22%. Both formulations at the 3-g dose reduced triglycerides by about 41%. IR niacin elevated HDL-C by 35% at the 3-g dose, while SR niacin elevated HDL-C by only 9.4%, a significant difference.

Both formulations were associated with considerable side effects. Nine of the 23 patients assigned to IR niacin withdrew from the trial before completing the 3-g dose phase because of adverse reactions, including vasodilation (flushing, itching, rash), fatigue, and acanthosis nigricans (a wart-like skin eruption). Eighteen of the 23 patients in the SR niacin group withdrew before completing the 3-g dose phase because of gastrointestinal effects, fatigue, and hepatotoxicity. Thus, 39% of patients on IR niacin and 78% of those on SR niacin withdrew because of side effects.

More than half the patients in the SR niacin group showed evidence of hepatotoxicity. Liver aminotransferase levels were three times the upper limit in 12 of the 18 who withdrew, and 3 patients had symptoms of hepatic dysfunction (fatigue, nausea, anorexia). Toxicity appeared dose related; changes in liver function test results reached statistical significance by the time the dosage reached 1500 mg/day, and 9 of the 12 with substantial hepatotoxicity were taking 2 to 3 g/day. Hepato-toxicity did not develop in any patients taking IR niacin.

In recent years, numerous case reports have described hepatotoxicity linked to high-dose niacin therapy; almost all the patients were taking SR niacin. Toxicity was noted in some cases in as little as 1 week after initiating therapy, and in others as late as 48 months. Usually, toxicity resolved after drug discontinuation, but in some cases liver dysfunction progressed to stage 3 and 4 encephalopathy, and one patient required liver transplantation. Perhaps even more hepatotoxi- city would have developed in patients in the McKenney study if the trial had continued beyond 5 weeks. Other major side effects reported in the literature include activation of peptic ulcers, hyperuricemia and gout, and impaired glucose tolerance. While McKenney et al. noted no change in uric acid levels, they did see elevations in fasting glucose levels with increasing doses. The elevations were significant in the SR niacin group at doses of 2 g and over. By the end of the trial, six patients with normal glucose levels at baseline (three in each group) had fasting glucose levels above 7.8Êmmol/L (140 mg/dL). One patient taking IR niacin had a bleeding pep-tic ulcer, apparently from activation of peptic ulcer disease.

A number of products have been implicated in niacin-induced hepatotoxicity, including two prescription products: Nicobid from Rhone-Poulenc Rorer (Collegeville, PA) and Slo-Niacin from Upsher- Smith (Minneapolis). Other implicated products include Nature's Plus, Niatrol, Endur-Acin, and generic products from Rugby Laboratories (Rockville Center, NY), Major Pharmaceuticals (San Diego), and Goldline Laboratories (Ft. Lauderdale, FL). According to Goldline, their SR niacin is a generic version of Rhone-Poulenc's Nicobid. Neither Goldline nor Rhone-Poulenc promote their SR niacin for cholesterol reduction. Only two prescription products (both of them IR niacin) are approved for cholesterol reduction: Upsher-Smith's Niacor and Rhone-Poulenc's Nicolar. "All other IR dosage forms and all SR dosage forms are available as nonprescription drugs for the treatment of nicotinic acid deficiencies and are not regulated by the FDA," said McKenney et al. In many published cases, a patient went to the health food store for IR niacin because of the health claims and the price, switched to SR niacin because of side effects associated with IR niacin, and then had to visit the doctor because of symptoms that turned out to be caused by hepatotoxicity. "Given the degree of toxic effects we encountered," said the investigators, "we believe that allowing niacin to remain on the nonprescription market, where it may be used in high doses for cholesterol lowering without proper monitoring by trained health care professionals, presents a potentially serious public health problem."

This study poses some interesting questions. Why was SR niacin more effective than IR niacin in reducing LDL-C? Why was IR niacin more effective for increasing HDL-C? Do phar-macokinetic differences explain the efficacy and toxicity differences? Slower absorption of SR niacin may mean lower peak serum levels, but fewer side effects may mean higher total ingested dose. Increased hepatotoxicity with SR niacin may be due to steadier bathing of liver cells, and the hepato-toxicity may explain the cholesterol reductions.

According to editorialist Louis Lasagna, the FDA has approved niacin for treating hypercholesterolemia, and the National Cholesterol Education Program recommends it for primary prevention. Niacin still has a role in managing dyslipidemia, said Lasagna, "but not on the basis of self-diagnosis and self- treatment." The Medical College of Virgin-ia cholesterol research center routinely evaluates the efficacy and safety of drugs for hypercholesterolemia. "The incidence and severity of adverse reactions experienced with both niacin dosage forms in the present study, but particularly with SR niacin, were much greater than any investigational drug we have evaluated for hypercholesterolemia," concluded McKen-ney et al. "If niacin were being evaluated for efficacy and safety and our experiences were replicated by others, we do not believe that it would be approved by the FDA for use in the management of hypercholesterolemia." (McKenney JM et al. JAMA. 1994;271:672-677. Lasagna L. JAMA. 1994;271:709-710)