Cardiac troponin T in pregnant women having intravenous tocolytic therapy

We studied drug-induced cardiotoxic effects in 22 pregnant women having tocolysis with intravenous fenoterol and verapamil. Because CK-MB is released from the uterus and placenta, we used the determination of cardiac troponin T (cTnT) as it is one of the most sensitive and specific indicators of myocardial necrosis. Cardiac troponin T levels were within physiological range (0.08 +/- 0.01 microgram/l) in all healthy pregnant women tested between 32 and 36 weeks of gestation (control group). In the pregnant women having tocolysis cTnT levels started to increase slightly during the first day of treatment (0.10 +/- 0.03 microgram/l) and were significantly higher (p < 0.05) during the third day (0.35 +/- 0.14 microgram/l) of tocolytic therapy. The cTnT levels in cord blood (0.13 +/- 0.03 microgram/l) did not correspond with maternal cTnT concentrations.

[Effect of continuous intravenous tocolysis with beta 2-mimetics and magnesium sulfate on erythropoietin level]

14 pregnant women receiving continuous intravenous tocolysis for threatened miscarriage were studied for an effect of beta 2-mimetics on erythropoiesis in humans. After tocolytic therapy for 48 h, the hematokrit fell by 14%; conversely erythropoietin levels rose by 88.7%. Increased erythropoiesis was reflected in increased reticulocyte (and reticulocyte subpopulation) counts. There was a significant correlation between cumulative tocolytic dose and erythropoietin elevation at 48 h. The hypervolemia evidenced by the decreased hematocrit was due to the increased oral fluid intake and fluid retention, and was the presumed main cause of the elevated erythropoietin levels. This effect could enhance understanding of the control of erythropoietin secretion. A similar mechanism may account for the increase in erythropoietin levels in pregnancy.

[What dosage is sufficient in combined inhalation therapy (fenoterol + ipratropium bromide) in patients with exacerbation of chronic obstructive lung disease?]

The authors compared in a prospective study the bronchodilatating and undesirable effects of combined inhalation treatment (phenoterol + ipratropium bromide) in the treatment of patients with exacerbation of chronic obstructive pulmonary disease, using different dosages. The patients were divided at random into two groups--group one inhaled berodual sol 3.5 ml/day (i.e. 1.75 mg phenoteroli + 0.875 mg ipratropii bromidium), the second group had a dose of double size. During the trial the authors monitored the peak expiration rate, the heart and respiration rate, blood gases and the subjective state of dyspnoea, using a 10 cm line. By comparison of bronchodilatating and undesirable effects they reached the conclusion that a daily dose of 3.5 ml berodual sol. is sufficiently effective. Increasing the daily dose to 7 ml did not produce a greater therapeutic effect nor increase the risk of undesirable effects.

[Tocolysis with a nitroglycerin patch]

We would like to present a 22 year old nullipara where preterm labor was successfully tocolysed using a nitro-glycerine path without sequellae side effects. Potential advantages and disadvantages of a transdermal nitro-glycerine delivery system in comparison to the commonly used intravenous fenoterol tocolysis is discussed.

Case-control study of salmeterol and near-fatal attacks of asthma

BACKGROUND

A case-control study was undertaken to investigate the hypothesis that the use of the long acting beta agonist salmeterol increases the risk of a near-fatal attack of asthma.

METHODS

The cases comprised admissions to the intensive care unit (ICU) for asthma in 14 major hospitals within the Wessex region in 1992. For each of the cases four age-matched controls were selected from asthma admissions to the same hospital during the same period. Information on prescribed drug therapy for the 48 cases and 185 controls was collected from the hospital admission records.

RESULTS

The patients admitted to the ICU had greater chronic asthma severity and had generally been prescribed more asthma drugs than the control admissions to hospital. The relative risk of a near-fatal attack of asthma in patients prescribed inhaled salmeterol was 2.32 (95% CI 1.05 to 5.16), p = 0.04. However, the salmeterol relative risk decreased to 1.42 (95% CI 0.49 to 4.10), p = 0.52 when the analysis was restricted to the more chronically severe patients (those in the subgroup of patients with a hospital admission for asthma in the previous 12 months). These findings suggest that the increased unadjusted relative risk with salmeterol is predominantly due to confounding by severity--that is, the increased relative risk is due to patients with more severe asthma (at greatest risk of a near-fatal asthma attack) being preferentially prescribed salmeterol. This interpretation is supported by the finding in this study that, within the control group (selected from the population of asthmatics requiring hospital admission), salmeterol was preferentially prescribed to the most severe patients (a threefold greater prescription of salmeterol to control patients if they had been admitted to hospital in the 12 months prior to the index admission). There was no increased risk of a near-fatal attack of asthma in patients prescribed a beta agonist by metered dose inhaler (OR 0.75 (95% CI 0.31 to 1.78), p = 0.51). In contrast, the relative risks for beta agonists delivered by nebulisation (OR 3.86 (95% CI 1.99 to 7.50), p < 0.001) and oral theophylline (OR 2.45 (95% CI 1.26 to 4.78), p < 0.01) were increased and did not markedly decrease when the analysis was restricted to the more severe asthmatic subjects.

CONCLUSIONS

Although these findings are not conclusive, particularly because of the small numbers involved in some subgroup analyses, they suggest that the use of salmeterol by patients with chronic severe asthma is not associated with a significantly increased risk of a near-fatal attack of asthma. If a near-fatal asthma attack is considered to be an intermediate step in a process by which a severe attack of asthma may become fatal, these results would suggest that salmeterol is unlikely to be associated with an increased risk of death, at least by this mechanism.

Optical illusions from visual data analysis: example of the New Zealand asthma mortality epidemic

The abundance of health-related statistics routinely collected worldwide invites their misuse from haphazard associations between secular trends of these data. This misuse is often compounded by assessing these associations simply on the basis of a visual inspection of the data. The visual approach to data analysis, known to have several pitfalls, is particularly tempting in the context of asthma where it has often been used. For example, the epidemic of asthma deaths that occurred in New Zealand during the last two decades has been imputed to fenoterol, a medication for asthma, on the basis of a visual assessment of ecological data. The simultaneity of time trends in the asthma death rate and fenoterol market share in that country formed an important part of the statistical basis of the evidence. We verified whether the results of such visual analyses are corroborated by more objective quantitative statistical methods of analysis. We reanalyzed these same data, namely the time trend data of New Zealand asthma death rates, fenoterol market share, sales of beta-agonists and inhaled corticosteroids, measured yearly for the 16-year span 1976-1991, using Poisson weighted loglinear regression. We found that the protective effect of inhaled corticosteroids (rate ratio 0.5 per canister per month; 95% confidence interval 0.4 to 0.7; p = 0.0001) was more closely associated with changes in asthma mortality than either fenoterol (RR 2.7 per canister per month; 95% CI: 0.9 to 7.5; p = 0.06) or all beta-agonists combined (RR 1.6; 95% CI: 0.8 to 3.0; p = .19). We conclude from this quantitative analysis that these ecological asthma mortality data provide evidence of a stronger association with inhaled corticosteroids, little used in New Zealand at the onset of the epidemic but used abundantly at its termination, than with fenoterol. This conclusion is diametrically opposite to that found by the visual approach. The quantitative analysis demonstrates that the visual approach to the analysis of ecological data, although seemingly convincing, can be misleading by creating an optical illusion. This purely visual approach to data analysis may thus have serious implications when the resulting scientific information is used to make vital public health and policy decisions.

International trends in sales of inhaled fenoterol, all inhaled beta-agonists, and asthma mortality, 1970-1992

To evaluate the hypothesis that fenoterol or all inhaled beta-agonists caused an epidemic of asthma mortality in New Zealand from the late 1970s to the mid-1980s, we examined trends from 1970 to 1992 in per capita sales of inhaled fenoterol, inhaled beta-agonists, and asthma mortality in New Zealand and nine other countries that marketed fenoterol. During the last two decades, there has been a large and widespread increase in sales of inhaled beta-agonists, including fenoterol. Asthma mortality in most countries, however, has been relatively stable. Only New Zealand experienced an epidemic of asthma mortality. In addition, sales rates of fenoterol similar in magnitude to those in New Zealand near the peak of the epidemic also occurred in Belgium, Austria, and Germany, while asthma mortality in these countries remained low. Also, sales rates of all beta-agonists in Australia were similar to those in New Zealand, but no epidemic of asthma mortality occurred in Australia. Therefore, the difference between asthma mortality rates in New Zealand and other countries is not explained by differences in per capita sales of fenoterol or all beta-agonists. Within New Zealand, the beginning and end of the epidemic correlated with a rise and fall in sales of all beta-agonists, including fenoterol. From 1980 to 1989, however, sales of fenoterol and all beta-agonists doubled in New Zealand while asthma mortality declined by 40%. International data on medication sales and asthma mortality, therefore, do not point to a relation between asthma mortality and beta-agonists in general nor fenoterol in particular.

Hypokalaemia in pregnant women treated with the beta 2-mimetic drug fenoterol--a concentration and time dependent effect

The effect of tocolytic treatment with fenoterol on plasma potassium concentrations was studied in 83 pregnant women on intravenous tocolytic therapy. Plasma concentrations of fenoterol and potassium were measured simultaneously, the time interval between initiation of therapy and taking the blood sample varying from 2 hours to 100 days. In a subset of 13 patients this blood sample was taken after two hours of therapy and pretreatment potassium concentrations were measured also. Pretreatment potassium concentrations were normal in these 13 patients and declined to 2.88 mmol/L (median) fenoterol concentrations being 320 ng/L through 1164 ng/L. Potassium concentrations measured later than 24 hours after initiation of therapy were all in the normal range corresponding fenoterol concentrations varying from 200 ng/L to 2504 ng/L. The multivariate statistical model for the description of all data showed that the duration of treatment was the only variable which explained the data to a significant extent. This might indicate that tolerance to the potassium lowering effect of fenoterol had developed within 24 hours after initiation of therapy. In the subset of 13 patients pretreatment potassium concentrations were found to be more important in explaining potassium concentrations than fenoterol concentrations at two hours. As we did not observe any adverse events in patients with low potassium concentrations and potassium concentrations were normal within 24 hours, we conclude that hypokalaemia due to fenoterol in the treatment of premature labor is not of clinical concern.

Therapeutic equivalence of a novel HFA134a-containing metered-dose inhaler and the conventional CFC inhaler (Berodual) for the delivery of a fixed combination of fenoterol/ipratropium bromide. A randomized double-blind placebo-controlled crossover study in patients with asthma

The efficacy and safety of a novel fenoterol/ipratropium bromide metered-dose inhaler (MDI) formulated with a non-chlorinated propellant, HFA134a, has been compared with placebo and the conventional chlorofluorocarbon (CFC)-containing fenoterol/ipratropium bromide inhaler (Berodual) in asthmatic patients. Fifty-two patients were enrolled in two centres. The fenoterol/ ipratropium bromide treatment produced significantly (P < 0.0001) greater bronchodilatation than placebo. There were no significant differences between the mean peak and average forced expiratory volume in the first second (FEV1) for patients receiving 2 puffs of the fenoterol/ipratropium bromide HFA134a inhaler and the conventional CFC inhaler. In addition, time to onset and duration of efficacy were comparable for these two treatments. None of the patients showed a fall of > or = 15% in baseline FEV1 or needed rescue medication within 30 min after inhalation of the test drug. No paradoxical bronchoconstriction was observed as measured by sGaw. The two inhaler formulations were well tolerated. A taste-related complaint, lasting for a few minutes after inhalation, was reported by a higher proportion of patients who inhaled the HFA134a formulation, mainly by patients selected in one of the two centres. In conclusion, a dose of 100 micrograms fenoterol/40 micrograms ipratropium bromide inhaled from a MDI containing HFA134a propellant is safe and provides effective bronchodilatation of equivalent degree, onset and duration of action to the same dose from the conventional CFC formulation.

Confounding by indication and channeling over time: the risks of beta 2-agonists

A previously published nested case-control study, the Saskatchewan Asthma Epidemiologic Project (SAEP) spanning 1980-1987, investigated the risk of fatal or near fatal asthma and found different risks for two inhaled beta 2-agonists, fenoterol and salbutamol. The authors assessed whether this comparison was confounded by indication because of channeling of inhaled fenoterol to more severely afflicted asthmatics. Using three subcohorts selected from a cohort of 12,301 asthmatics assembled from the computerized databases of Saskatchewan Health and followed over 7 years, the authors studied two forms of channeling and investigated whether greater asthma severity and less well-controlled disease were associated with preferential prescribing of a first prescription of inhaled fenoterol, as opposed to inhaled salbutamol, and whether they were associated with the likelihood of a switch from inhaled salbutamol to fenoterol as well as a switch from inhaled fenoterol to salbutamol. The authors found that the initial choice between fenoterol and salbutamol was independent of the severity of the asthma and disease control, but that preferential prescribing of fenoterol occurred among users of salbutamol who showed signs of increased severity or uncontrolled asthma. The switch from inhaled fenoterol to salbutamol was, however, minimally related to asthma severity. They conclude that the comparison between inhaled fenoterol and salbutamol in the SAEP may have been biased by indication. This study demonstrates that long-term information on medication use is essential to ensure that the results of such case-control studies are not biased by indication.

[Long-term effects of inhaled beta 2-agonists on bronchial hyperresponsiveness in asthmatics]

We examined the effects of two year's treatment of three inhaled beta 2-agonists (beta 2), such as salbutamol (S), procaterol (P) and fenoterol (F) on acetylcholine induced bronchial hyperresponsiveness (BHR) in mild approximately moderate asthmatics. When symptomatic use of beta 2 were less than 6 puffs/day, BHR was improved significantly with both S and P but was not with F. When more than 6 puffs/day, all three beta 2 did not show the improvement of BHR. Without the effect of corticosteroids, BHR was improved with S, and was partially improved with P in case of only less than 6 puffs/day, but was not improved with F unrelated to the inhaled puff number. Therefore, frequent use of beta 2 even if used only on demand was shown to worse BHR, asthmatics must be controlled to under the good condition of using beta 2 at least less than 6 puffs/day.