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Alteration of methyldopa absorption, metabolism, and blood pressure control caused by ferrous sulfate and ferrous gluconate
Author(s) -
Campbell N,
Paddock V,
Sundaram R
Publication year - 1988
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1038/clpt.1988.47
Subject(s) - methyldopa , ferrous , blood pressure , chemistry , sulfate , medicine , organic chemistry
This study examined the effect of two widely used iron treatments on methyldopa absorption, metabolism, and blood pressure control. A 500 mg tablet of methyldopa (2.37 mmol) was taken with and without ferrous sulfate (325 mg) by 12 normal subjects in a randomized crossover trial. When ferrous sulfate was taken with methyldopa there was a decrease in the proportion of methyldopa excreted as “free” methyldopa (49.5% ± 12.4% vs 21.1% ± 4.77%; p < 0.01), a significant increase in the proportion excreted as methyldopa sulfate (37.8% ± 12.3% vs 65.8% ± 10.5%; p < 0.01), and a decrease in the percentage of methyldopa absorbed (29.1% ± 12.5% vs 7.88% ± 4.14%; p < 0.01). These factors resulted in an 88% reduction in the quantity of “free” methyldopa excreted. To determine if an iron preparation without sulfate produced the same effect, the study was repeated with ferrous gluconate (600 mg) with similar results. The clinical consequences of the methyldopa–ferrous sulfate interaction was determined in five hypertensive subjects receiving chronic methyldopa therapy. The subjects took ferrous sulfate for 2 weeks. There was an increase in both systolic and diastolic blood pressure in four patients and a decrease in blood pressure in all patients after ferrous sulfate was discontinued. The increases in blood pressure were substantial in three of the patients. Clinical Pharmacology and Therapeutics (1988) 43, 381–386; doi: 10.1038/clpt.1988.47