Actions of salbutamol in late pregnancy: plasma cyclic AMP, insulin and C-peptide, carbohydrate and lipid metabolites in diabetic and non-diabetic women

Labetalol, a combined alpha- and beta-blocker, in hypertension of pregnancy

Labetalol was given to women with hypertension of pregnancy in their last trimester to study its acute effect on circulation and metabolism. Seven women were given 50 mg labetalol i v. There was a significant decrease of blood pressure from a mean of 143/101 +/- 4/2 (SEM) to 127/88 +/- 5/2 mm Hg. Maternal heart rate fell significantly from 77 +/- 5 to 68 +/- 3 beats per min. These changes persisted during a three-hour observation period. The hypotensive response was accompanied by a significant increase in plasma noradrenaline from 1.54 +/- 0.16 to 2.37 +/- 0.41 nmol/l, suggesting sympathetic activation. Plasma cyclic AMP, which is increased by beta 2-adrenoceptor stimulation, was significantly elevated after labetalol. This supports the hypothesis of partial beta-agonist activity of labetalol. Lipid metabolism, as judged from measurements of plasma FFA, glycerol and 3-hydroxybuturic acid, showed little change. The acute effect of labetalol on uteroplacental blood flow was determined in eight women with pregnancy hypertension using a gammacamera on line with a computer. 0.5 mCi indium-113m was given i v before and 30 min after labetalol was administered i v in a dose of 1 mg per kg body weight. After the injections of indium-113m, serial scintigrams were recorded during 10 s periods for 240 s. By computerized summation of the scintigrams, an image was obtained in which the placenta could be outlined for time-activity analysis of the isotope accumulation curve. From this curve a uteroplacental blood flow index could be calculated. Labetalol induced a significant drop of mean arterial blood pressure from 114 +/- mm Hg to 100 +/- 3 mm Hg after 30 min in this group of women. However, the uteroplacental blood flow index did not change. As we have earlier shown with this technique that uteroplacental blood flow can be severely impaired in hypertension of pregnancy, the finding of substained uteroplacental blood flow simultaneously with a decrease in blood pressure should be of clinical importance. Taken together with other studies of clinical effects, these results indicate that labetalol is useful in the treatment of hypertension of pregnancy.

Effect of nebulized albuterol on blood glucose in patients with diabetes mellitus with and without cystic fibrosis

Over 90% of cystic fibrosis (CF) patients are treated with bronchodilators, and 6% have diabetes. Some with asthma also have diabetes, and most are treated with bronchodilators. Systemic administration of adrenergic agents can cause increases in blood glucose, but the effect of inhaled agents is unclear. A double-blind study was performed on 10 patients with type 1 diabetes mellitus (DM) without CF (3 male, 7 female, mean age 25.5 years) and 9 patients with insulin-dependent CF-related diabetes (CFRD) (8 male, 1 female, mean age 21.9 years). On 2 separate days before 9 AM fasting and the morning dose of insulin, 2.5 mg of albuterol or nebulized placebo were given. Blood glucose was measured by finger stick with a glucose reflectance meter before and 15, 30, 45, and 60 min after treatment. No significant changes from baseline or differences between placebo and albuterol occurred in either group. The mean maximum increase from baseline in DM was 20 mg/dl on placebo, and 38 mg/dl on albuterol; in the CFRD, the respective changes were 7 and 7 mg/dl. Two DM patients had a > 50 mg/dl increase on albuterol vs. placebo; no CFRD patients had differences of such magnitude. DM patients had greater increases from baseline than CFRD patients on placebo and albuterol. Differences reached statistical significance at 30 and 45 min on placebo, and 45 min on albuterol. Albuterol 2.5 mg by nebulizer causes no clinically significant increases in blood glucose in DM or CFRD patients. Diabetes patients without CF have a significantly greater increase of glucose with time (placebo or albuterol) than CFRD patients.

Sympathomimetics for acute severe asthma: should only beta 2-selective agonists be used?

Sympathomimetics have become a mainstay of the treatment of acute asthma. Aerosolization of sympathomimetics provides as great or greater bronchodilation in acute severe asthma with fewer systemic effects than parenteral therapy. Despite the broncho-selectivity achieved with this route of administration, cardiostimulation remains the major, dose-limiting factor in the safe use of sustained, high-dose therapy with these agents. This article reviews the pharmacology, adverse effects, and toxicities of selected beta agonists, as well as clinical studies relevant to the question posed in the title. Although the ideal study to answer this question has not yet been performed, the authors feel that available evidence supports the preferential use of selective beta 2 agonists in patients with acute, severe asthma who will require high doses of beta agonists.

The actions of tulobuterol on isolated preparations of gravid human myometrium

1. The effects of tulobuterol (Abbott 54173) on the contractile force developed by electrically stimulated strips of gravid (gestation 36-40 weeks) human uterine muscle were compared with those of isoprenaline and adrenalin. 2. Isoprenaline produced inhibition of electrically evoked contractions of myometrium from 12 of 17 women at concentrations at or below 1 mumol/L (range 0.001-1 mumol/L). It enhanced contractions at concentrations of 10-50 mumol/L. In tissues from the remaining five women isoprenaline produced neither inhibitory nor excitatory effects. Adrenalin (0.1-50 mumol/L) was found to enhance contractile force in a concentration-dependent manner (EC50 = 0.30 mumol/L). 3. In the presence of metoprolol (0.3 mumol/L), a selective antagonist at beta 1-adrenoceptors, the isoprenaline concentration-response relationship was shifted to the left, indicating that beta 1-adrenoceptors are present and that they mediate excitation in the human uterus. 4. In contrast tulobuterol (in neither the presence nor absence of metoprolol), in the same concentration range as isoprenaline and adrenalin, (0.001-50 mumol/L) was found to have no effect on the electrically evoked contraction of gravid human uterine muscle strips.

Beta-adrenergic receptor responsiveness to isoprenaline in humans: concentration-effect, as compared with dose-effect evaluation and influence of autonomic reflexes

1. Different techniques of assessing beta-adrenoceptor sensitivity in vivo, by use of i.v. infusions or bolus injections of isoprenaline (ISO), were compared in healthy volunteers. The importance of autonomic reflexes for responses to ISO was evaluated by studying the influence of 'autonomic blockade' by atropine and clonidine, which antagonize muscarinic effects and reduce sympathetic activity, respectively. Estimates of in vivo responsiveness to ISO were compared with parameters reflecting beta 2-adrenoceptor function in vitro in lymphocytes. 2. Heart rate responses to infused ISO were not significantly altered by 'autonomic blockade' when evaluated from concentration-effect curves. When related to the infused dose of ISO, however, sensitivity was artefactually increased (P less than 0.05), as the plasma concentrations of ISO were 40% higher after atropine and clonidine. Heart rate responses to bolus injections of ISO were attenuated (P less than 0.05) by 'autonomic blockade', suggesting that facilitatory reflexes contribute to these non-steady state responses. Intersubject variations in heart rate responsiveness to ISO were greater than the intrasubject variability caused by counterregulatory reflexes. 3. 'Autonomic blockade' lowered venous plasma noradrenaline at rest. The noradrenaline response to ISO infusion was attenuated and the diastolic blood pressure response enhanced, indicating that a counterregulatory vasoconstrictor reflex normally is activated by ISO-induced vasodilatation. The plasma cyclic AMP response to ISO, on the other hand, was unaffected by atropine and clonidine and reflects beta 2-adrenoceptor responsiveness in vivo. 4. In vitro data for beta-adrenoceptor binding sites (Bmax;[125I]-IHYP binding) and cyclic AMP responses to ISO in lymphocytes correlated with DBP and noradrenaline responses to infused ISO. No correlations were found between in vitro data and heart rate, plasma cyclic AMP or plasma glycerol responses to infused ISO in vivo. 5. During prolonged ISO infusions (in six other healthy subjects) physiological responses reached greater than 90% of their steady state level after 8 min, but no definite steady state level could be defined for the plasma concentration of ISO during 40 min of infusion. 6. The ISO infusion test showed a good reproducibility, especially when repeated on the same day. Evaluation of plasma concentration-effect relationships increase the precision of the ISO infusion test as confounding inter- and intra-individual variations in ISO concentrations (as caused by e.g. autonomic blockade) will be taken into account.(ABSTRACT TRUNCATED AT 400 WORDS)

Adverse reactions to beta 2-agonist bronchodilators

Beta 2-Agonists are safe and effective bronchodilator drugs. Their major adverse effects of skeletal muscle tremor, tachycardia and various metabolic effects are mediated by beta-adrenoceptor stimulation and are reversible. Skeletal muscle tremor is the most frequent dose-limiting side effect. It may be reduced by commencing treatment with a low dose and if it persists another beta 2-agonist may be tried. Other side effects such as cardiac arrhythmias and reduction in PaO2 are a serious potential problem in some susceptible asthmatics. However, they are infrequent or of a mild degree and are generally outweighed by the good control of asthma produced by beta 2-agonists. Side effects from beta 2-agonist therapy can be minimised by use of the inhaled route which selectively delivers the drug to the airways. Furthermore, selective tolerance develops to their side effects. The dose of a beta 2-agonist should be assessed on the basis of therapeutic effect and the level of tolerance to its side effects. Recommended doses of beta 2-agonists used for long term therapy do not cause clinically significant desensitisation of airway beta-adrenoceptors, although this may become a relevant problem in patients who are regularly receiving very high doses. Intravenous beta 2-agonists have a place in the treatment of severe asthma not responding to nebuliser therapy. In this life-threatening situation with severe airflow obstruction, monitoring of heart rate, PaO2, plasma potassium and the electrocardiogram should be mandatory and supplemental oxygen given so that serious adverse effects are presented.

Development of tolerance to oral salbutamol in the third trimester of pregnancy: a study of circulatory and metabolic effects

1 The purpose of the study was to investigate whether a development of tolerance does occur or not to salbutamol-induced cardiovascular and metabolic effects after oral long term treatment in pregnancy. 2 Twenty-three women in late pregnancy were given an oral dose of 4 mg salbutamol in the morning after an overnight fast. Ten of the women had not been exposed to beta-adrenoceptor agonists earlier in their pregnancy (group A). Thirteen of the women had been treated with salbutamol in a dose of 4 mg four times a day for 12 to 33 days preceding the study (group B). 3 Blood samples were collected every 30 min for 120 min and analyzed for cyclic AMP, insulin, C-peptide, glucose, lactate, glycerol, non-esterified fatty acids (NEFA) and 3-hydroxybutyrate (3-HB). Heart rate and blood pressure were recorded simultaneously. 4 In group A there was significant increase in plasma cyclic AMP and increased glycogenolysis, lipolysis and insulin secretion. In this group there were also significant cardiovascular effects, that is, an increase of heart rate and decrease of diastolic blood pressure. 5 In group B the effects of salbutamol were significantly less pronounced, indicating a development of tolerance. 6 We conclude that the metabolic side-effects are not sufficient reason to withhold beta-adrenoceptor agonists to healthy pregnant women with threatened premature labour, since tolerance rapidly develops to these actions.

Circulatory and metabolic effects of a combined alpha- and beta-adrenoceptor blocker (labetalol) in hypertension of pregnancy

1 Seven women with hypertension of pregnancy were given the combined alpha- and beta-adrenoceptor blocking drug labetalol (50 mg i.v.) in their last trimester. Acute effects were studied for 3 h after administration. 2 Systolic and diastolic blood pressures were significantly reduced from 143 +/- 4 (s.e. mean) to 127 +/- 5 mmHg and from 101 +/- 2 to 88 +/- 2 mmHg, respectively. Maternal heart rate fell significantly from 77 +/- 5 to 68 +/- 3 beats/min. The changes remained during the 3 h of observation. Foetal heart rate was not affected. No side-effects were encountered. 3 Plasma noradrenaline increased significantly from 1.54 +/- 0.16 to a peak value of 2.37 +/- 0.41 nmol/l suggesting sympathetic activation following labetalol. Plasma adrenaline levels were essentially unchanged. Plasma glucose, insulin and C-peptide showed only minor changes. No major effects on lipid metabolism were seen except a significant fall of nonesterified fatty acids at 60 min. Plasma cyclic AMP increased significantly throughout the observation period, perhaps indicating beta-adrenoceptor agonist activity of labetalol. 4 The effectiveness of labetalol as an acute hypertensive agent together with apparent absence of metabolic disturbances and other side-effects makes it an interesting drug for the treatment of hypertension during pregnancy.

Insulin-induced hypoglycaemia in diabetic women during late pregnancy and one year post partum

Insulin (0.1 IW/kg) later followed by glucose was injected intravenously in nine diabetic women in the supine position both during pregnancy and one year post partum. C-peptide was present in five subjects, indicating some residual beta-cell function. Their mean basal C-peptide level, before insulin, was twice as high in the pregnant as inthe non-pregnant state. C-peptide decreased progressively after insulin. The mean basal plasma glucose level was lower during pregnancy (4.8 mmol/l) than after it (9.6 mmol/l), but decreased to the same level (2.2 mmol/l) after insulin. The rate of fall in glucose was thus lower during pregnancy (kt = 2.54) than after (kt = 4.08), but was unrelated to the basal glucose levels. Basal levels of free fatty acids (FFA), 3-hydroxybutyrate (3-HB), cyclic AMP, and lactate were similar, while glycerol was lower during pregnancy. Insulin-induced changes in FFA, glycerol, 3-HB, cyclic AMP, and lactate were similar during and after pregnancy. Plasma amino acid concentrations were generally lower in pregnancy, significantly so only for arginine and glycine. Amino acid levels were unaffected by insulin in pregnancy, whereas leucine, isoleucine and tyrosine decreased significantly in the non-pregnancy, whereas leucine, isoleucine and tyrosine decreased significantly in the non-pregnancy, whereas leucine, isoleucine and tyrosine decreased significantly in the non-pregnancy state. We conclude that there are differences in metabolic responses to insulin in diabetic women during and after pregnancy, indicating a decreased sensitivity to insulin during pregnancy in some tissues.

Metabolic and circulatory effects of oral salbutamol in the third trimester of pregnancy in diabetic and non-diabetic women

Metabolic and cardiovascular effects of 4 mg oral salbutamol were studied in ten non-diabetic, ten chemical diabetic and five juvenile diabetic women in late pregnancy. None of the women had been treated with beta-sympathomimetic drugs earlier in their pregnancy. Heart rate and blood pressure were recorded and blood samples for measurement of plasma cyclic AMP, insulin, C-peptide, glucose, lactate, glycerol, non-esterified fatty acids (NEFA) and 3-hydroxybutyrate (3-HB) were collected every 30 minutes for 120 minutes after salbutamol. All women underwent the same procedure at random without salbutamol. There were significant cardiovascular effects of salbutamol in all the groups but no differences in these effects between the groups. Salbutamol caused significant increases of glycogenolysis and lipolysis in all the groups, significantly larger in the juvenile diabetic than the non-diabetic and chemical diabetic women. This observation could be explained by the inability of the juvenile diabetics to secrete insulin, shown by their non-measureable plasma C-peptide levels. The metabolic responses following salbutamol in the chemical diabetics were intermediate between the non-diabetic and juvenile diabetic groups. The results show that diabetes does not alter the sensitivity of beta-receptors involved in cardiovascular regulation, while the metabolic responses to oral salbutamol are enhanced, especially in juvenile diabetics. We suggest that during treatment with beta-sympathomimetic drugs, blood glucose should be monitored in all patients showing criteria of potential diabetes.

Single injection of terbutaline in term labor: placental transfer and effects on maternal and fetal carbohydrate metabolism

Maternal and fetal blood glucose and insulin levels were studied in 10 women in the second stage of labor after administration of terbutaline, 250 micrograms intravenously. The transport of the drug across the placenta was also studied. Saline solution was administered to four other women who served as controls. A rise in maternal plasma insulin levels occurred in all patients but was more pronounced in patients treated with terbutaline less than 25 minutes before delivery than in those treated more than 45 minutes prior to delivery. No difference was found in maternal blood glucose levels between terbutaline-treated patients and controls. Blood glucose increased in the fetuses during the second stage of labor and paralleled that of the mothers, but on a lower level. None of the newborn infants demonstrated hypoglycemia during the first 90 minutes after birth. Terbutaline crossed the placenta rapidly, and fetal plasma levels up to 55% of the maternal plasma levels were found. The conclusion is that this form of administration of terbutaline does not seem to have any negative short-term influences on the fetal carbohydrate metabolism.

Anaphylactic shock in monkeys passively sensitized with human reaginic serum. II. Respiratory mechanics, hematology and metabolism

Seven monkeys were passively sensitized intravenously (i.v.) with human serum containing IgE antibodies specific to dog albumin. I.v. administration of the antigen resulted in an immediate increase in pulmonary resistance (Rpulm) with a concomitant decrease in pulmonary dynamic compliance (Cdyn). Initially these changes in the respiratory system resulted in pronounced effects on venous admixture, arterial oxygen saturation (SaO2) and arterial pH. After 30 min, as Rpulm and Cdyn returned towards control levels, the blood gas changes were mainly due to low cardiac output. There was a transient increase in hematocrit, a decrease in plasma fibrinogen and a transient reduction in the number of circulating leukocytes. The anaphylactic reaction resulted in a 10- to 30-fold increase in plasma adrenaline with time and in a substantial but less marked increase in plasma noradrenaline and dopamine. Probably as a consequence of the increase in plasma catecholamine, there was a rise in plasma cyclic AMP, glucose and glycerol. No increase in plasma histamine levels was found. In two animals sensitized with purified IgE a reaction which was less severe but had the same general pattern was observed. The findings show that IgE-mediated anaphylaxis in the monkey results in a bronchoconstriction leading to a profound respiratory disturbance characterized by decreased SaO2 due to increased venous admixture. After 30 min these variables were normalized and the shock state was dominated by poor tissue perfusion due to a low cardiac output.

Effects of acetylsalicylic acid on plasma glucose, free fatty acid, betahydroxybutyrate, glucagon and C-peptide responses to salbutamol in insulin-dependent diabetic subjects

The selective beta 2-adrenergic agonist salbutamol increases plasma glucose concentration and the rate of lipolysis when infused in pregnant diabetic women. The aim of the present study was twofold: (a) to focus on the actions of salbutamol on lipid and carbohydrate metabolism in insulin-dependent diabetics: and (b) to investigate possible interferences of acetylsalicylic acid (ASA) with the metabolic responses to i.v. salbutamol. The results obtained during salbutamol infusion (5 microgram/min) in 6 insulin-dependent diabetic subjects demonstrated that this drug caused sustained increases in plasma glucose, free fatty acid and beta-hydroxybutyrate concentrations, as well as a small and transient rise of plasma glucagon. No change in plasma C-peptide concentration occurred during salbutamol. A concurrent infusion of lysine acetylsalicylate reduced the increase in free fatty acids by half, blunted the weak glucagon response but enhanced the rise in plasma glucose following salbutamol administration. The present data show that salbutamol exerts a potent hyperglycemic, lipolytic and ketogenic effect in insulin-dependent diabetics. We suggest that this beta-adrenergic agent should be used cautiously in human diabetes mellitus.

A case report of maternal death associated with betamimetics and betamethasone administration in premature labor

A fatal case of pulmonary edema is reported after prolonged treatment with beta-mimetics during pregnancy for threatened premature labor. The mother had received betamethasone in order to enhance fetal lung maturity. Myocardial failure occurred 5 days after discontinuation of betamimetics. The potential toxic effects of beta-adrenergic agents and their association with corticosteroids are discussed. Caution is recommended when high doses of betamimetics are to be delivered to prevent premature labor. No patient should be treated unless her cardiac condition is normal. Cardiovascular evaluation should be regularly performed during the course of treatment. No patient should be discharged after treatment without a normal cardiovascular check-up.

Cyclic AMP and metabolic substrates following hemorrhage in awake and anesthetized rats

The levels of several metabolites in plasma were studied during a period of 4 h in awake and barbiturate anesthetized rats after a blood volume loss of approximately 3% of b.w. Blood pressure was 70 mmHg (9.3 kPa) in the awake and 35 mmHg (4.7 kPa) in the anesthetized rats. Resting levels of plasma glucose, blood lactate and pyruvate and plasma cyclic AMP were higher in the awake rats than in the anesthetized rats. Bleeding caused an increase of plasma glucose in both groups. There was a more rapid increase in blood lactate and pyruvate as well as in plasma cyclic AMP levels in the awake rats than in the anesthetized rats. By contrast, plasma glycerol levels were unaltered by bleeding, and plasma FFA levels were decreased in both groups. At the end of the 4-h bleeding period plasma glucose was higher and blood lactate levels were lower in the awake rats. The initial changes in plasma metabolite levels appeared to be directly related to changes in plasma catecholamine levels. There were no differences in the relationship between the adrenaline level and cyclic AMP or glucose increase, suggesting that anesthesia did not alter beta-adrenoceptor sensitivity, but only catecholamine concentrations. The results also indicate that awake rats tolerate long-lasting blood volume loss better than anesthetized rats, because the sympatho-adrenal activation is more short-lasting.

Management of premature labour in diabetic pregnancy

The practical management of premature labour is described, illustrated by ten cases. All the patients were treated with beta-sympathomimetic infusion, either salbutamol (0.4-1.6 mg/h) or ritodrine hydrochloride (2-6 mg/h), to stop uterine contractions, and with intramuscular dexamethasone 4 mg eight hourly to accelerate foetal lung maturity. Satisfactory control of blood glucose was achieved (range 2-10 mmol/l) by using high rates of insulin infusion (range 8-32 units per hour). Delivery was postponed in eight cases and seven healthy babies were born. There were three foetal deaths from multiple congenital abnormalities. Beta-sympathomimetic infusion caused few maternal side-effects and there were no foetal problems. Maternal plasma potassium decreased in all cases studied, the mean fall being from 4.5 mmol/l to 2.7 mmol/l.

Comparison of hormonal and metabolic effects of salbutamol infusion in normal subjects and insulin-requiring diabetics

A comparison of the metabolic effects of salbutamol in diabetic patients and normal subjects showed that salbutamol infused at 5 and 2 microgram/min (a) stimulated hepatic glucose production to a greater extent in diabetic patients than in normal subjects despite prior restoration of the diabetic patients' fasting blood glucose to normal by an overnight infusion of insulin; (b) caused a greater rise in plasma glucose, free fatty acids, glycerol, and ketone-body concentrations in the diabetic patients; and (c) produced a marked fall in plasma-potassium concentrations. The differences between the diabetic and normal groups were accounted for by an immediate (six-fold) stimulation of insulin secretion in the normal subjects.