Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.

Omacor (Abbott)
1000 mg capsules
Approved indications: hypertriglyceridaemia, secondary prevention following myocardial infarction
Australian Medicines Handbook section 6.5.4

A diet rich in fish oils has long been associated with cardiovascular benefits.1The components of fish oil include omega-3 polyunsaturated fatty acids. Ethyl esters of two of the acids, docosahexaenoic acid and eicosapentaenoic acid, are contained in the new product. There is currently no complete explanation of how these esters act on triglycerides and the cardiovascular system.

There have been several studies of omega-3-acids and a meta-analysis found that they significantly reduce triglyceride concentrations by 0.3 mmol/L.2In an early study, 57 patients with combined hyperlipidaemia were randomised to take the esters or corn oil as an adjunct to diet. After 12 weeks serum triglycerides had reduced by 28% (estimated 1.12 mmol/L absolute change) in the 28 patients who took the esters, but only slightly reduced in those given corn oil. Both treatments significantly reduced total cholesterol, but only slightly increased high density lipoprotein (HDL) cholesterol.3

The product has also been studied in 59 patients with serum triglycerides above 2.3 mmol/L who were taking simvastatin. They were randomised to add the omega-3-acid ethyl esters or a placebo for 24 weeks. Serum triglycerides fell from a mean of 4.6 to 3.5 mmol/L with active treatment, but the mean increased with placebo from 3.8 to 3.9 mmol/L. These changes were unrelated to the patients' simvastatin doses.4

A larger trial also studied hypertriglyceridaemia in patients taking simvastatin. After dietary advice and taking open-label simvastatin for eight weeks, 256 patients were randomised to add omega-3-ethyl esters or placebo. After a further eight weeks the mean triglyceride concentration had fallen from a baseline value of 282 mg/dL to 202.4 mg/dL (3.19 to 2.29 mmol/L) with the esters and from 286.7 to 275.9 mg/dL (3.24 to 3.12 mmol/L) with placebo. HDL cholesterol increased by 1.8 mg/dL (0.047 mmol/L) with the esters and decreased by 0.7 mg/dL (0.018 mmol/L) with placebo.5

The indications for using the esters in hypertriglyceridaemia are restricted. The product is only approved as monotherapy for type IV and V dyslipidaemia. It can be added to therapy of type IIb dislipidaemia if a 'statin' does not produce adequate control.

The main study supporting the use of the esters in secondary prevention after myocardial infarction involved 11 324 patients. They were randomised to take vitamin E, the esters, both or neither. After 3.5 years the relative risk of death, non-fatal myocardial infarction and non-fatal stroke had reduced by 10% in the patients who took the esters compared with those who did not. There was a 26% reduction in the risk of sudden death. Adding vitamin E to the esters did not significantly add to their efficacy.6The dose used was 25% of the 4 g recommended for dyslipidaemia so there were only small changes in lipids. This suggests that another mechanism may explain the beneficial effects of the esters after myocardial infarction.

Approximately 4% of patients will stop taking omega-3-acid esters because of adverse effects. Compared with placebo, patients taking them complain more frequently of altered taste and gastrointestinal upsets. Liver function should be monitored in patients with liver dysfunction. Fish oils may prolong the bleeding time, within normal limits, so this effect should be considered if the patient is being anticoagulated or taking aspirin. High doses may increase the concentration of low-density lipoprotein cholesterol. It is uncertain if patients who are allergic to fish have an increased risk of adverse reactions.

Fish oils are an option in the treatment of certain dyslipidaemias. The amount required cannot easily be obtained from the diet. Eating oily fish several times a week may be enough for patients after myocardial infarction. Although the secondary prevention trial showed benefits, they depended on how the data were analysed. In one analysis the esters did not have a significant effect on cardiovascular deaths, non-fatal myocardial infarctions and non-fatal strokes. A systematic review of omega-3-fatty acids found they did not significantly reduce the risk of death or cardiovascular events.7If they are used for secondary prevention, it is important that the patient also takes the standard therapies used after myocardial infarction.

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  1. Beilin LJ. Fish oils and prevention of cardiovascular disease. Aust Prescr 1987;10:42-55.
  2. Balk EM, Lichtenstein AH, Chung M, Kupelnick B, Chew P, Lau J. Effects of omega-3 fatty acids on serum markers of cardiovascular disease risk: a systematic review. Atherosclerosis 2006;189:19-30.
  3. Grundt H, Nilsen DW, Hetland O, Aarsland T, Baksaas I, Grande T, et al. Improvement of serum lipids and blood pressure during intervention with n-3 fatty acids was not associated with changes in insulin levels in subjects with combined hyperlipidaemia. J Intern Med 1995;237:249-59.
  4. Durrington PN, Bhatnagar D, Mackness MI, Morgan J, Julier K, Khan MA, et al. An omega-3 polyunsaturated fatty acid concentrate administered for one year decreased triglycerides in simvastatin treated patients with coronary heart disease and persisting hypertriglyceridaemia. Heart 2001;85:544-8.
  5. Davidson MH, Stein EA, Bays HE, Maki KC, Doyle RT, Shalwitz RA, et al. Efficacy and tolerability of adding prescription omega-3 fatty acids 4 g/d to simvastatin 40 mg/d in hypertriglyceridemic patients: an 8-week, randomized, double-blind, placebo-controlled study. Clin Ther 2007;29:1354-67.
  6. GISSI-Prevenzione Investigators. Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Lancet 1999;354:447-55.
  7. Hooper L, Thompson RL, Harrison RA, Summerbell CD, Ness AR, Moore HJ, et al. Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review. BMJ 2006;332:752-60.