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Preparation of (R) and (S) alpha methyldopa from a chiral hydantoin containing the alpha phenylethyl group.

Chiral hydantoin (S)-1 was prepared in good yield from phenyl isocyanate and N-[(S)-alpha-phenylethyl]glycinate, (S)-3. Enolate (S)-1-Li was methylated in high yield and good diastereoselectivity. In contrast, a second alkylation reaction of methylated enolate (S)-4-Li proceeded with essentially no diastereoselectivity. Nevertheless, dialkylated hydantoins, (S,S)-7 and (S,R)-7, could be readily separated by flash chromatography and subsequent hydrolysis of either derivative afforded the desired (S)-L-alpha-methyldopa or (R)-D-alpha-methyldopa in good yield.

Alkylation↗

Effect of alpha-methyldopa on cardiac output in hypertension.

Hemodynamic and blood volume changes, systolic time intervals, and baroreflex mechanisms were studied in 20 patients with hypertension after methyldopa (12 +/- 0.9 mg/kg/day). The drug was administered orally during 7 days' hospitalization on a normal sodium diet (110 mEq/day). There was a fall in blood pressure and in total peripheral resistance, without significant change in cardiac index, heart rate, and stroke index. There were increases in plasma and blood volume (p less than 0.05) but no change in cardiopulmonary blood volume or systolic time intervals. The unchanged heart rate was associated with an increased sensitivity ( less than 0.05) of the baroreflex mechanisms. The study supports the view that the unchanged cardiac output after methyldopa is related to important changes in control of cardiac output, including redistribution of blood volume and modifications in baroreflex mechanisms.

Adult↗

Blood lipid effects of antihypertensive therapy: a double-blind comparison of the effects of methyldopa and propranolol.

Thirty-two middle-aged men with essential hypertension completed a double-blind randomly allocated comparison of the effects of methyldopa versus propranolol on blood lipid levels. After a four-week period on a placebo for each drug, subjects were titrated for the next six weeks with either methyldopa from 500 to 2000 mg/day or propranolol from 80 to 320 mg/day plus a placebo for the other drug until supine diastolic blood pressure was below 90 mm Hg or the ceiling dose was reached. Subjects were then maintained on the achieved drug dose for an additional six weeks and finally switched back to a placebo for each drug for four more weeks. Blood lipid levels were measured twice during each study period and the values averaged and compared. Neither drug significantly affected levels of total plasma cholesterol. However, both drugs reduced high-density lipoprotein (HDL) cholesterol levels about 10 per cent and increased the total cholesterol to HDL cholesterol ratio. In addition, propranolol significantly increased plasma triglyceride levels (28.3 per cent). The changes in lipid levels were not dose related. Whether or not these blood lipid changes persist and their possible clinical implication during prolonged therapy remain to be elucidated.

Aged↗

Effects of methyldopa on psychometric performance.

Double-blind, crossover comparisons of methyldopa with placebo were performed in 16 patients with mild to moderate hypertension. Methyldopa (250 mg tid) for 14 days significantly reduced blood pressure, impaired card-sorting time and digital symbol substitution score, and caused trends for impairment of other psychometric tests. Effects of practice were greater than those of treatment on all tests other than card sorting, although no interaction between treatment and practice was seen. Continued dosage impairs psychometric performance, but practice effect is a major confounder. Simple crossover studies are inadequate for detecting moderate drug effects on intellectual performance.

Adult↗

Determination of free methyldopa in plasma by high-pressure liquid chromatography and electrochemical detection.

A quantitative method for the analysis of free methyldopa in plasma is described. The method is based on reversed-phase high-pressure liquid chromatography with electrochemical detection utilizing an ion-pairing agent. Separation of methyldopa from plasma is achieved by alumina adsorption. The parameters associated with the adsorption step are described. The lower limit of sensitivity is similar to or approximately 10 ng of methyldopa/ml with a corresponding retention time of 6.9 min.

Acetonitriles↗

Reserpine and alpha-methyldopa in the treatment of tardive dyskinesia.

Thirty inpatients with evidence of tardive dyskinesia secondary to antipsychotic medications participated in this double-blind, controlled, randomized study comparing reserpine, alpha-methyldopa and placebo. Reserpine at doses of 0.75--1.5 mg daily, or alpha-methyldopa at doses of 750--1,500 mg daily, produced a statistically significant improvement in tardive dyskinesia symptomatology compared to the results obtained with placebo.

Adult↗

On the role of alpha-methyldopamine in the antihypertensive effect of alpha-methyldopa.

In renal hypertensive rats the cerebral concentration of alpha-methyldopa, alpha-methyldopamine, alpha-methylnoradrenaline, dopamine and noradrenaline as well as the blood-pressure were determined simultaneously. The antihypertensive effect followed a time course identical to that of the increase in the cerebral concentration of alpha-methyldopamine and of the decrease in the concentration of dopamine, whereas lowering of blood pressure on the one hand, and changes in the levels of alpha-methylnoradrenaline and noradrenaline, on the other, were not related to each other. Dose-response relationships showed the same correlations and lack of correlations, respectively. These results suggest that non-betat-hydroxylated catecholamines play a major role in mediating the antihypertensive effect of alpha-methyldopa or, alternatively, that only the newly biosynthesized alpha-methyl-noradrenaline is effective in lowering blood pressure.

Animals↗

Is alpha-methyldopa-type autoimmune hemolytic anemia mediated by interferon-gamma?

Drug-related autoimmune hemolytic anemia appearing with warm-reacting antibodies can be classified according to the offending substances. One of the subtypes can be induced by alpha-methyldopa. However, the pathophysiology of the underlying mechanism is not yet known. In parallel, patients with Parkinson's disease and other extrapyramidal disorders, who are under administration of dopaminergic drugs, often present with abnormal findings with respect to immune parameters. In order to reveal further mechanisms within the immune response, the capability of patients under dopaminergic medication to release cytokines after a stimulatory signal was examined. Therefore, 18 patients who were treated with the dopamine analogue lisuride were compared with an aged-matched control group of 21 healthy volunteers. After stimulation with phytohemagglutinin (PHA), mitogen-induced concentrations of interferon-gamma were significantly higher in the patients treated with lisuride than in the control group. Interferon-gamma leads to an upregulation of MHC class-I and especially class-II molecules on antigen-presenting cells and to an induction of antibody production in B cells. This condition can result in the induction of an autoimmune process. It might be supposed that alpha-methyldopa-type autoimmune hemolytic anemia is mediated by elevated levels of interferon-gamma produced in T cells after a stimulatory signal.

Anemia, Hemolytic, Autoimmune↗

Reversal of left ventricular hypertrophy in hypertensive patients treated with methyldopa. Lack of association with blood pressure control.

Ten patients with essential hypertension and left ventricular hypertrophy were treated with relatively small doses of methyldopa (500 to 750 mg/day) added to long-term diuretic therapy. Sequential M mode echocardiography showed significant reduction in left ventricular mass 36 weeks after addition of methyldopa in four patients (359 +/- 77 [standard error of the mean] to 235 +/- 63 g) although blood pressure was not significantly altered by the added treatment. In three of these patients, reduction of left ventricular mass was observed as early as 12 weeks of treatment (384 to 262 g). Neither left ventricular mass to left ventricular volume ratio nor fractional shortening was significantly altered by reduction in left ventricular mass (3.21 +/- 0.26 to 2.74 +/- 0.24 and 0.42 +/- 0.03 to 0.44 +/- 0.02, respectively). There was no apparent relation in these patients between changes in blood pressure and changes in left ventricular mass. Thus, reversal of cardiac hypertrophy with antihypertensive treatment is possible in human beings; however, it seems to depend on other factors besides blood pressure control.

Adult↗

Effect of methyldopa on menopausal flushes, skin temperature, and luteinizing hormone secretion.

The effect of methyldopa (100 mg intravenously), the precursor of the alpha-receptor agonist alpha-methylnorepinephrine, on subjectively experienced menopausal flushes, skin temperature, and luteinizing hormone secretion was investigated in seven women in a double-blind, saline-controlled, crossover study. Subjects were monitored over a 3-hour period. Methyldopa significantly decreased the number of subjective flushes (p less than 0.05) and the number of cutaneous temperature peaks (p less than 0.05) but had no effect on the number of luteinizing hormone secretory pulses, variability of luteinizing hormone secretion, or total luteinizing hormone secretion. These studies indicate that alpha-adrenergic mechanisms (central and/or peripheral) play a role in the pathophysiology of menopausal flushes.

Climacteric↗

Effects of reserpine, guanethidine and methyldopa on cardiac output and its distribution.

In anaesthetized rats with a renal model of hypertension, effects of reserpine, guanethidine and methyldopa on cardiac output (the dye-dilution method) and its distribution among the heart, the lung, the kidney, the large and small intestine, the stomach, the liver, the spleen, skeletal muscle and skin (the rubidium method) were studied. Several hours administration of all three drugs under study, a definite decrease in cardiac output was observed. Cardiac output then escaped from the influence of the drugs despite a reduction in heart rate. Fall of arterial pressure 24 hr after administration of the drugs was only due to the decrease in total peripheral resistance. Effects of the drugs on distribution of cardiac output were studied at the time when cardiac output was not changed to any significant extent. Under this condition the features common to all the drugs were an increase of the cardiac output fractions to the gastro-intestinal tract and a decrease to the heart and the spleen. This fact indicates that decrease in resistance of gastro-intestinal vascular region plays a basic role in the hypotensive effect of reserpine, guanethidine and methyldopa.

Animals↗

Comparative effects of alpha-methyldopa, propranolol and hydralazine therapy on cardiac adenylate cyclase activity in normal and spontaneously hypertensive rats.

Normotensive (WKY) and spontaneously hypertensive (SHR) male rats were treated orally, one week after weaning and for 9 weeks, with alpha-methyldopa (100 mg/kg per day), propranolol (30 mg/kg per day) or hydralazine (10 mg/kg per day). Untreated WKY and SHR rats served as controls. The development of hypertension in SHR rats were attenuated by treatment but none of the drugs was able to restore the impairment in isoproterenol, secretin and glucagon responsiveness of cardiac adenylate cyclase activity which is characteristic of these animals. In heart membranes from both WKY and SHR rats, alpha-methyldopa treatment increased the number of beta-adrenoceptors by 20-32% and the maximal response of adenylate cyclase activity to isoproterenol and glucagon by 20-34%. By contrast, the beta-blocker propranolol was ineffective on these parameters. The results obtained are consistent with the hypothesis that the change in adenylate cyclase seen in SHR rats is genetic in origin and is not a consequence of hypertension.

Adenylyl Cyclases↗

Management of pregnancy-induced hypertension with pindolol--comparative study with methyldopa.

Thirty-two consecutive women with pregnancy-induced hypertension of early onset were randomly allocated to treatment with pindolol or methyldopa. There was no difference between the groups in regard to the average time of delivery (36.33 vs. 36.6 weeks) and weight of the newborn (2850 vs. 2870 g). A significant drop in systolic (P less than 0.005) and diastolic (P less than 0.05) blood pressure was observed in the group of patients treated with pindolol as compared with the methyldopa group. In the pindolol group an improvement in renal function was observed as determined by CCT and serum creatinine. There were no side effects from the drugs in the mother or in the newborn.

Adult↗

Oral drug reaction to methyldopa. Report of a case.

This case report presents and follows a rare oral drug reaction linked to the administration of methyldopa (Aldomet). The clinical appearance of oral ulcerations coincides with increased dosage of the drug. Withdrawal of methyldopa leads to gradual healing of these lesions.

Aged↗

Methyldopa-induced autoantibodies against red blood cells.

Methyldopa therapy results in the formation of red cell autoantibodies in 10-20% of patients taking the drug for longer than 4 months. These red cell antibodies are true autoantibodies, that is they are directed against an autoantigen on the red blood cell membrane and not against the drug or against a drug-altered antigen. The target membrane antigen is usually within the Rhesus system, although often the antibody specificity cannot be defined. Red cell antibody is usually detectable in the patient's sera as well as on the red cells. The autoantibody is usually a warm reacting IgG antibody. Most patients who develop these autoantibodies do not go on to develop hemolytic anemia in spite of high titres of antibodies on their red cells. In addition, these patients do not tend to develop hemolysis if methyldopa therapy is continued. Rarely patients develop hemolytic anemia which can be severe. Differences in antibody characteristics, including subclass restriction, complement-binding ability, or titre do not explain why some patients with autoantibody hemolyze while most do not. One group of investigators found that hemolyzing patients had IgM on their red cells while those who did not had IgG only. But while this observation could explain why some patients (IgM-sensitized red cells) hemolyze, it does not explain why most patients with IgG-sensitized red cells do not hemolyze. Why the autoantibody forms is not known but some investigators have proposed that the drug may directly affect B or T cells with resulting impairment of immune tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia, Hemolytic, Autoimmune↗

Toxicity studies of amphetamine sulfate, ampicillin trihydrate, codeine, 8-methoxypsoralen, alpha-methyldopa, penicillin VK and propantheline bromide in rats and mice.

Thirteen-week toxicity studies in F344/N rats and B6C3F1 mice were conducted to determine general toxicity and target organ toxicity with amphetamine sulfate, ampicillin trihydrate, codeine, 8-methoxypsoralen, alpha-methyldopa sesquihydrate, penicillin VK, and propantheline bromide. This paper discusses the toxicity observed; use of the toxicity data to set dose levels for subsequent 2-year studies; and comparison of dose levels administered to rodents with doses used in the treatment of human disease. Drugs were administered orally in the feed or by gavage. The lowest doses in the 13-week studies were comparable to therapeutic doses in man on a mg/m2 (body surface area) basis or 5-10 times doses used in man on a mg/kg body weight basis. Little toxicity was seen at the low dose level with ampicillin, penicillin VK, 8-methoxypsoralen or propantheline bromide. At higher doses, target organ toxicity seen included the urinary bladder in male rats after propantheline bromide; the glandular stomach in rats and mice after penicillin VK; the liver and adrenals in rats after 8-methoxypsoralen; and the kidney in mice and rats after alpha-methyldopa. After amphetamine, codeine, or ampicillin administration, no target organ toxicity was seen in rats or mice, even at doses which caused body weight gain depression. The high doses chosen for subsequent 2-year studies were within 10 times human dose levels when compared on a mg/m2 body surface area.

Ampicillin↗

Neurobehavioral teratogenic effects of clomipramine and alpha-methyldopa.

Neonatal treatment of rats with centrally acting drugs such as clomipramine was shown to affect adult body and brain weight, behavior and sleep. We made a further study of the effects of clomipramine and tested one dose of alpha-methyldopa. Male rats were treated twice daily with saline, 7.5 or 15 mg/kg clomipramine or 100 mg/kg alpha-methyldopa from postnatal day 2-14 and tested in adulthood for effects on acquisition of radial maze behavior, on problem solving behavior in Hebb-Williams mazes, sexual performance and sleep-wake patterns. Clomipramine-treated rats had reduced body weight. No effects of neonatal drug treatment were found on several measures in the two mazes. Ejaculating rats in all three treatment groups showed longer latencies for sexual behavior and clomipramine-treated rats showed fewer ejaculations. Clomipramine-treated rats spent more time sleeping than the controls during the 24 hr sleep-wake recordings in adulthood.

Animals↗

A rapid high performance liquid chromatographic determination of methyldopa in human serum with fluorescence detection and alumina extraction: application to a bioequivalence study.

A simple and ultra rapid high performance liquid chromatographic (HPLC) method coupled with alumina extraction and fluorescence detection was described for determination of methyldopa in human serum. The drug and an internal standard were adsorbed onto alumina and eluted using acidic methanol. The eluate was directly injected onto ODS reverse phase column using a mixture of phosphate buffer (0.05 M) containing triethylamine (100 microl/l, v/v; pH 2.3) and methanol (92:8, v/v) at a flow rate of 2.1 ml/min as the mobile phase. The fluorescence detector excitation and emission wavelengths were set at 270 and 320 nm, respectively. No interference in the assay from any endogenous substances or other concurrently used drugs was observed and the retention times of I.S. and the drug were 1.7 and 2.4 min, respectively with total run time (injection to injection) of less than 3.5 min. The limit of quantification was evaluated to be 2 ng/ml. Validity of the method was studied and the method was precise and accurate with a linearity range from 20 ng/ml to 5000 ng/ml. This method has been used in a randomized crossover bioequivalence study of two different methyldopa preparations in 24 healthy volunteers.

Aluminum Oxide↗