Clinical evidence,mechanism, importance and management
In a study 36 patients with mild hypertension were given either propranolol 80mg daily or fish oil 9 g daily (as capsules and equivalent to eicosapentaenoic acid 1.8 g and docosahexaenoic acid 1.1 g daily) for 36 weeks followed by placebo for 4 weeks. A further group of 16 patients were given propranolol 80mg daily for 12 weeks,propranolol plus fish oil 9 g daily for 12 weeks, propranolol plus fish oil placebo for 12 weeks, and finally propranolol placebo for 4 weeks. Fish oil alone decreased blood pressure to a similar extent to propranolol, and decreases in blood pressure with combination were greater than with either propranolol or fish oil alone (See reference number 1). A further similar study in 14 patients taking a beta blocker found that when they were also given 4 capsules of Omacor (equivalent to eicosapentaenoic acid 1.9 g and docosahexaenoic acid 1.5 g) daily for 6 weeks their blood pressure decreased by a further 3.3/1.9 mmHg (See reference number 2).
The mechanism is uncertain, but as fish oil seems to have a hypotensive effect of its own, it may enhance hypotensive effect of any beta blocker.
Singer P,Melzer S, Goschel M, Augustin S. Fish oil amplifies the effect of propranolol in mildessential hypertension. Hypertension (1990) 16, 682–91.
Lungershausen YK,Abbey M, Nestel PJ, Howe PRC. Reduction of blood pressure and plasmatriglycerides by omega-3 fatty acids in treated hypertensives. J Hypertens (1994) 12, 1041–5.