Combined oral contraceptives are associated with increasedblood pressure and may antagonise efficacy of antihypertensive drugs. However, effects are far greater with high-dosecontraceptives that were used historically, and risks appear tobe smaller with newer low-dose contraceptives.
Clinical evidence,mechanism, importance and management
Early after introduction of combined oral contraceptives it was realised that they can cause increases in blood pressure and clinical hypertension (See reference number 1,2). One study,(See reference number 3) from 1970s, in 83 women found that average rise in blood pressure was 9.2/5 mmHg, and that it was about twice as likely to occur as in those not on pill. Additionally,cases were noted where antihypertensives (at that time, commonly guanethidine and/or methyl-dopa) were not that effective in women with hypertension on combined oral contraceptives (See reference number 2,4). Although modern combined oral contraceptives are lower dose,they are still associated with a small increased risk of elevated blood pressure (See reference number 5). A UK study found that combined oral contraceptives were associated with a 2.6/1.8 mmHg rise in blood pressure,whereas progestogen-only oral contraceptives did not affect blood pressure (See reference number 5). Furthermore, in a study in 24 postmenopausal women with hypertension taking enalapril 10mg twice daily use of enalapril with drospirenone/estradiol 3/1 mg (12 women) produced a significant decrease in blood pressure of 9/5 mmHg after 14 days of treatment, when compared with placebo group (12 patients). No serious adverse effects were reported (See reference number 6). Note that drospirenone is an analogue of spironolactone,and shares some of its effects, including its blood pressure-lowering effects.
This is only a very brief review of this subject, but risks of hypertension with combined hormonal contraceptives appear to be modest. Nevertheless, they need to be considered in context of other possible cardiovascular risk factors. Where possible,blood pressure should be monitored before and during contraceptive use.
Wallace MR. Oral contraceptives and severe hypertension. Aust N Z J Med (1971) 1,49–52.
Woods JW. Oral contraceptives and hypertension. Lancet (1967) iii,653–4.
Weir RJ,Briggs E, Mack A, Naismith L, Taylor L, Wilson E. Blood pressure in women takingoral contraceptives. BMJ (1974) 1, 533.
Clezy TM. Oral contraceptives and hypertension: the effect of guanethidine. Med J Aust (1970) 1,638–40.
Dong W,Colhoun HM, Poulter NR. Blood pressure in women using oral contraceptives: results from the Health Survey for England 1994. J Hypertens (1997) 15, 1063–8.
Preston RA,Alonso A, Panzitta D, Zhang P, Karara AH. Additive effect of drospirenone/17ß-estradiol in hypertensive postmenopausal women receiving enalapril. Am J Hypertens (2002) 15, 816–22.