Essential hypertension and oxidative stress: New insights

Table 1 Clinical trials accounting for strategies using antioxidants in essential hypertension

Details of Study	Study	n	Results	Ref.
Intrabrachial vitamin C (2.4 mg/100 mL forearm tissue per minute)	Randomized placebo-controlled trial	28	In hypertensive patients but not in control subjects, vitamin C increased the impaired vasodilation to acetylcholine	[141]
Intra-arterial infusion of vitamin C at 24 mg/min for 10 min	Randomized trial	16	Forearm blood flow response to acetylcholine was significantly enhanced with intra-arterial infusion of vitamin C in hypertensive group before antihypertensive treatment	[142]
Oral administration of 500, 1000 or 2000 mg of vitamin C once daily	Randomized double-blind, placebo-controlled trial	31	Significant diminution of mean systolic blood pressure and diastolic blood pressure, with no differences between the increasing doses of vitamin C	[143]
Chronic supplementation of 600 mg/daily of vitamin C	Randomized placebo-controlled trial	24	Reduced systolic blood pressure and pulse pressure in ambulatory elderly patients, but not in adult group	[144]
Included 29 trials of vitamin C supplementation	Meta-analysis	-	In short-term trials, vitamin C supplementation reduces systolic and diastolic blood pressure	[145]
Crossover design Placebo or antioxidant combination: 200 mg zinc 500 mg vitamin C 600 mg vitamin E 30 mg of β-carotene	Randomized double-blind placebo-controlled trial	38	Combined therapy of antioxidants showed that systolic blood pressure fell significantly on hypertensive subjects	[80]
Oral supplementation: 1 g vitamin C 400 UI vitamin E or Placebo for 8 wk	Randomized double-blind, placebo-controlled, crossover study	30	Treatment with vitamins C and E has beneficial effects on endothelium-dependent vasodilation in untreated essential hypertensive patients	[153]
Oral supplementation: 1 g vitamin C 400 UI vitamin E or Placebo for 8 wk	Randomized double-blind placebo-controlled trial	110	Specific association between oxidative-stress related parameters and blood pressure Patients with essential hypertension had significantly lower systolic, diastolic and mean arterial blood pressure	[146]
ACEI plus NAC (600 mg three times a day) or ACEI only	Randomized controlled trial, crossover study	18	Significant decrease in systolic and diastolic blood pressure with the combination of ACEI and NAC compared to ACEI-only	[147]
Standard therapy or Melatonin plus antihypertensive standard therapy	Randomized controlled trial	170	Combined therapy had better outcomes than standard therapy alone on essential hypertensive patients	[148]
Intra-arterial administration: NAC (48 g/min) or vitamin C (18 mg/min)	Cross-over randomized study	30	The intra-arterial administration of NAC had no effect on endothelium-dependent vasodilation Intra-arterial vitamin C improved endothelium-dependent vasodilation	[151]
Coenzyme Q10, 100 mg twice daily or placebo	Randomized, double-blind, placebo-controlled crossover study	30	There was not statistically significant reductions systolic or diastolic blood pressure	[150]
Vitamin C supplement daily Either 50 mg or 500 mg, for 5 yr	Randomized double-blind controlled trial	244	Neither systolic nor diastolic blood pressure was significantly related with the serum vitamin C concentration	[152]

ACEI: Angiotensin-converting enzyme inhibitors; NAC: N-Acetylcysteine.