Biomedical subjects

L W van Elferen

Publications and source records attributed to L W van Elferen.

6 recordsLinked to original sources

PubMed1996

Randomised comparison between a loading and incremental dose model for ritodrine administration in preterm labour.

OBJECTIVE: To compare a new loading dose regimen for intravenous ritodrine administration in preterm labour with the conventional dose regimen. DESIGN: Multicentre randomised trial using numbered opaque sealed envelopes. SETTING: Five teaching hospitals in the Netherlands. PARTICIPANTS: Women (n = 203) in preterm labour at less than 34 weeks of gestation. INTERVENTIONS: Women received either a loading dose ritodrine infusion followed, as soon as tocolysis was reached, by a decrease in infusion rate or the conventional schedule of increasing doses until uterine quiescence was achieved. RESULTS: Frequency of successful tocolysis (71%) and duration of treatment (55 h) were similar in both groups, but the loading dose schedule was better tolerated with fewer adverse events. Also the number of dose adjustments was smaller than in the incremental dose group (P < 0.001). Overall, the differences between the two regimens were unexpectedly small. CONCLUSIONS: Despite the small differences, the loading model is easier to apply, requires fewer dose adjustments, is better tolerated with less side effects, and reduces the likelihood of clinical error.

Dose-Response Relationship, Drug↗

PubMed1996

Double-blind evaluation of ritodrine sustained release for oral maintenance of tocolysis after active preterm labour.

OBJECTIVE: To evaluate the effect of ritodrine sustained release capsules for maintaining uterine quiescence after successful treatment of active preterm labour. DESIGN: Multicentre placebo-controlled trial. SETTING: Five teaching hospitals in the Netherlands. PARTICIPANTS: Women (n = 95) at less than 35 weeks of gestation in whom active preterm labour had been stopped with intravenous ritodrine. INTERVENTIONS: Women received either two 40 mg ritodrine sustained release capsules (n = 50) or identical placebo capsules (n = 45) three times a day for seven days. RESULTS: The proportion of women who received another course of active treatment was significantly smaller with the sustained release than with placebo (1 of 50 versus 11 of 45: P = 0.003) as was the number delivering because of preterm labour during treatment (0 of 50 versus 4 of 45: P = 0.04). There were no other significant differences between the two groups. CONCLUSIONS: Maintenance treatment with ritodrine sustained release capsules after arrest of preterm labour reduces the risk of recurrences of preterm labour that necessitate treatment or precipitate delivery.

Administration, Oral↗

PubMed1993

A loading model for ritodrine administration in preterm labour.

OBJECTIVE: To develop a ritodrine infusion scheme for preterm labour that avoids plasma levels above those needed for tocolysis, requires only one rate adjustment, and is easy to apply in practice. DESIGN: Prospective study of tocolytic effect and plasma ritodrine concentrations during application of the infusion scheme. SETTING: High risk labour ward. SUBJECTS: Consecutive series of 31 women in labour at less than 36 weeks' gestation. INTERVENTION: Loading dose ritodrine infusion followed, as soon as tocolysis is reached, by a decrease in the infusion rate calculated on the basis of the interval between start of treatment and tocolysis. RESULTS: Overall, steady state ritodrine levels were nearly identical to those at the time of tocolysis and correlated well with levels anticipated on the basis of our calculation (n = 30; r = 0.91; P < 0.001). Adjustments during steady state were made in 12 women (40%), but in only two of them within 12 h after tocolysis had been reached. Delivery was postponed for more than 48 h in 29 women (93.5%) and beyond 37 weeks' gestation in 19 (61.3%). CONCLUSION: The loading model is easy to apply, avoids relative overdoses, requires few adjustments, is well tolerated, uses smaller quantities of ritodrine, and results in lower plasma ritodrine concentrations than the conventional infusion scheme.

Dose-Response Relationship, Drug↗

PubMed1987

A loading-dose infusion scheme for intravenous tocolysis with ritodrine: a pilot study.

A loading-dose infusion scheme for intravenous ritodrine therapy was tested in twelve patients with preterm labour. We started with a rather high (386 micrograms/min) infusion rate, but the moment tocolysis was reached this infusion rate was reduced to a level needed to maintain the plasma concentration then found. Plasma samples of ritodrine were taken the moment tocolysis was reached and in the steady state, and compared with each other and with expected and calculated plasma concentrations. In the dynamic loading phase we found a half-life for ritodrine of 1 h. This half-life of 1 h can be explained by cumulation of ritodrine in the central compartment and is therefore called cumulation t1/2. In developing an infusion scheme with a loading dose for ritodrine, this cumulation t1/2 of 1 h should be taken into account.

Adult↗

PubMed1987

A new administration form of ritodrine. Ritodrine plasma levels with sustained-release capsules in a steady state.

A sustained-release administration form of oral ritodrine was introduced to cope with the problem of the short dosage interval inherent to conventional oral ritodrine administration. The bioavailability of this application form was assessed in a clinical study including 11 patients. With a dosage frequency of only 3 times daily and a dosage form index of 1.8, plasma levels of 14.6-26.5 ng/ml ritodrine (equivalent to an infusion rate of approximately 50 micrograms/min) were obtained without serious cardiovascular or metabolic side effects. It was concluded that with this new formulation clinical applicability of orally administered ritodrine in tocolytic therapy has increased.

Administration, Oral↗

PubMed1978

Hemolysis during salicylazosulfapyridine therapy.

In 36 unselected patients with ulcerative colitis or Crohn's disease taking 4.5-6 gm. salicylazosulfapyridine per day the incidence of hemolysis and its relation to the serum level of salicylazosulfapyridine (Salazopyrin, Azulfidline, SASP), free sulfapyridine (SP) and acetyl sulfapyridine (ac-SP) was investigated. In 19 patients hemolysis was present. Serum levels of free SP were significantly higher in these patients (P less than 0.001). All patients with a serum SP level higher than 37 microgram./ml. had hemolysis as compared to only four of 21 patients with a serum SP level below 37 microgram./ml. Four patients had evidence of hemolytic anemia. In these patients the serum SP level was higher than 55 microgram./ml. Eighteen of the 19 patients with hemolysis were slow acetylators while six of the 17 patients without hemolysis belonged to the slow acetylator phenotype.

Adolescent↗