The Renal Excretion of Methyldopa

Myhre, E; Brodwall, E. K.; Stenbaek, O; Hansen, Tonya Moen

doi:10.3109/00365517209081076

Cited by 10 publications

(4 citation statements)

References 3 publications

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“…These estimates of the amount of free and conjugated oa-methyldopa in the infants at birth vary between 130-850 jg (mean 442 jg) and 275-1630 jg (mean 692 ig) respectively. They probably underestimate the free oa-methyldopa and overestimate the a-methyldopa sulphate, since Myhre et al (1972b) reported the volume of distribution of free drug to be in excess of the extracelular water volume in adults, while Myhre et al (1972a) state that about 50% of the a-methyldopa sulphate in plasma is bound to protein, so that the whole of the plasma concentration will not distribute throughout the extracellular water.…”

Section: Discussionmentioning

confidence: 99%

A study of the disposition of alpha‐methyldopa in newborn infants following its administration to the mother for the treatment of hypertension during pregnancy.

Jones¹,

Cummings²,

Setchell³

et al. 1979

Brit J Clinical Pharma

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Harrow, Middlesex HAl 3UJ1 The nine infants participating in this study were born to mothers who received continuous therapy with a-methyldopa (0.75-2.0 g/day) for several weeks extending to the time of delivery. 2 The concentration of free and total (free plus conjugated) a-methyldopa was determined by gas chromatography-mass spectrometry in amniotic fluid, umbilical cord plasma and maternal plasma at delivery; also in urine collected over timed intervals from neonates during the first days after birth. 3 The results indicate that a-methyldopa administered to the mother is present in the infant at birth at a level comparable to the maternal level and persists for some days. The ratio of conjugated to free drug increases with time after birth. 4 The excretion of free and conjugated a-methyldopa in the urine indicated that the drug is slowly eliminated in the neonate by excretion in the urine and apparently by metabolism, mainly to the sulphate conjugate. 5 The concentration of free and conjugated a-methyldopa in amniotic fluid tended to be higher than in umbilical cord plasma but lower than in neonatal urine, conjugated drug predominated.

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Section: Discussionmentioning

confidence: 99%

A study of the disposition of alpha‐methyldopa in newborn infants following its administration to the mother for the treatment of hypertension during pregnancy.

Jones¹,

Cummings²,

Setchell³

et al. 1979

Brit J Clinical Pharma

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“…e ImmatIon curves IS that extrarenal rug e Immation occurs, and that this mechanism is most• f Important at high plasma drug levels. In act We have found strong indications of such ã echanism (4). Extrarenal elimination of uncon-J~~ated methyldopa might also explain the drug e~l11ination in the case of anuria.…”

Section: Discussionmentioning

confidence: 61%

“…Another possibility is that ti l : second slope of the plasma elimination cU~e could be due to drug-induced reduction of t renal function, though we did not find dep~eS; sion of the GFR or renal plasma flow durill Short-term treatment with methyldopa (1). A self-depression of a renal transport mechanism eems unlikely, since the excretion of uncon-Jugated methyldopa is mainly a result of glomerular filtration (4).…”

Section: Discussionmentioning

confidence: 99%

Plasma Turnover of Methyldopa in Advanced Renal Failure

Myhre¹,

Brodwall²,

Stenbaek³

et al. 1972

Journal of Internal Medicine

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Methyldopa is one of the most useful drugs for treatment of hypertension in patients with reduced renal function. Few data are available on the metabolism of this drug in renal failure, therefore the plasma turnover rate has been determined in 8 patients with advanced renal failure and 11 cases with essential hypertension with no or only slightly reduced renal function. In both groups of patients a biphasic plasma elimination first was obtained after i.v. injection of the drug. The first, and quantitatively most important, part of the curve showed a half‐life of 3.6 hours in advanced renal failure compared to 1.7 in essential hypertension. A fairly good correlation was demonstrated between the half‐life of the drug in plasma according to the initial disappearance rate and the endogenous creatinine clearance. In patients with renal failure only 50–60% of the drug injected was eliminated during the initial phase, the remainder disappeared even more slowly. The slow, second phase of the elimination curve was also exponential with a slope corresponding to a T/2 of 7–16 hours. In patients with a drug was nearly normal renal function about 95% of the drug was eliminated during the rapid, initial phase. Our findings are in good agreement with the drug accumulation occurring in renal failure.

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“…These data are qualitatively similar to that reported in a smaller number of subjects.P The absolute levels of MD assayed in both groups of patients in the current study are somewhat lower than those reported using the fluorescent trihydroxyindole procedure. 14,15 This discrepancy may be due to our use of a more specific separation and detection system as well as a 3-hr-longer sampling interval.…”

Section: Resultsmentioning

confidence: 99%

Metabolie disposition of methyldopa in hypertensive and renal-insufficient children

O’Dea

Mirkin

1980

Clin Pharmacol Ther

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The serum levels of methyldopa and its principle metabolites were assessed in 22 hypertensive children, of whom 13 had impaired renal function. A significant correlation was found between the magnitude of the renal dysfunction and the serum levels of methyldopa, alpha-methyldopa-sulfate, alpha-methyldopamine, and alpha-methyldopamine-sulfate. The patients were divided into 2 groups: those with normal (serum creatinine less than or equal to 1.0 mg/100 ml) and those with abnormal (serum creatinine greater than 1.0 mg/100 ml) renal function. The serum level of alpha-methyldopa-sulfate and not of methyldopa was elevated in those with renal dysfunction. The serum levels of alpha-methyldopamine and, in particular, its 3-0 sulfate conjugate were markedly elevated in patients with renal disease. These data suggest that the enhanced sensitivity to methyldopa in patients with impaired renal function may be due in part to alpha-methyldopamine.

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The Renal Excretion of Methyldopa

Cited by 10 publications

References 3 publications

A study of the disposition of alpha‐methyldopa in newborn infants following its administration to the mother for the treatment of hypertension during pregnancy.

A study of the disposition of alpha‐methyldopa in newborn infants following its administration to the mother for the treatment of hypertension during pregnancy.

Plasma Turnover of Methyldopa in Advanced Renal Failure

Metabolie disposition of methyldopa in hypertensive and renal-insufficient children

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