Homogeneous enzyme immunoassay for theophylline in serum and plasma.

1. Eight volunteers were given seven doses of 200 mg of slow release theophylline at either 11.00 h and 23.00 h (regimen 1) or 17.00 h and 05.00 h (regimen 2). At the time of the sixth dose (60 h) hourly blood sampling was started and continued for 24 h. After at least 1 week volunteers crossed over to the other regimen. 2. Volunteers retired to bed at 23.00 h and arose after the 07.00 h sample during both regimens. 3. During regimen 1 there was a marked rise in mean tmax from 3.3 h after dosing at 11.00 h to 9.3 h after dosing at 23.00 h (P less than 0.001). There was also a fall in AUC(0,12) from 89.9 mg l‐1 h after dosing at 11.00 h to 79.0 mg l‐1 h after dosing at 23.00 h. There was no difference in mean Cmax values. 4. During regimen 2 these circadian changes were abolished with mean values after both dosing times lying between those observed during regimen 1. 5. A marked delay in absorption occurs at night and cannot be explained by food intake.

Section: Introduction Methodsmentioning

confidence: 99%

Circadian variation in theophylline absorption during chronic dosing with a slow release theophylline preparation and the effect of clock time of dosing.

Jackson

Johnston

Woollard

et al. 1988

“…1 h after completion of infusion) for measurement of plasma theophylline concentrations. An Emit homogeneous enzyme immunoassay was used (Chang et al, 1982).…”

Section: Methodsmentioning

confidence: 99%

Potentiation of the adverse effects of intravenous terbutaline by oral theophylline.

Smith¹,

Kendall²

1986

We have studied the influence of therapeutic plasma concentrations of theophylline on some of the unwanted responses to intravenous terbutaline in normal subjects. There was a significantly greater fall in serum potassium and rise in plasma glucose, pulse rate and systolic blood pressure in response to an intravenous infusion of terbutaline when theophylline was present compared with when terbutaline was given alone. These drugs are commonly used together in the treatment of acute asthma and potentiation of side effects may be hazardous. We suggest monitoring of the serum potassium when these drugs are used together during acute exacerbations of asthma.

“…Serum theophylline concentrations were determined using an enzyme mediated immunoassay technique (EMIT) (Chang et al, 1982). Both the within assay and between assay coefficient of variation (CV) at 5.4 mg 171 were < 4%.…”

Section: Methodsmentioning

confidence: 99%

The interaction between i.v. theophylline and chronic oral dosing with slow release nifedipine in volunteers.

Jackson¹,

Shah²,

Debbas³

et al. 1986

Eight healthy volunteers received a 5 min i.v. infusion of lysine theophylline, equivalent to 197 mg anhydrous theophylline, both before (day 1) and during (day 5) steady state chronic oral dosing with slow release nifedipine 20 mg 12 hourly. A theophylline pharmacokinetic profile was performed on day 1 and day 5 and a nifedipine pharmacokinetic profile was performed on day 4 and day 5. The greatest difference in serum theophylline concentrations was seen at the first sampling time (5 min after completion of the infusion) with a mean concentration of 9.9 mg l‐1 during nifedipine administration and 14.6 mg l‐1 with theophylline alone. Thereafter, the difference fell to approximately 1 mg l‐1 until 6 h when they became almost identical. Repeated measures analysis of variance using the theophylline serum concentrations at each of ten time points over 8 h as the repeated measures showed a small but significant effect of nifedipine (F(1,151) = 7.0, P less than 0.01) on serum theophylline concentrations. Mean volume of distribution (V) rose from 0.33 +/‐ 0.07 to 0.39 +/‐ 0.06 1 kg‐1 corrected body weight (CBW) in the presence of nifedipine (t = 2.23, P = 0.052). Theophylline clearance, area under the curve to 8 h AUC (0‐8), area under the curve to infinity AUC (0‐infinity) and elimination half‐life (t1/2) did not change appreciably. No statistically significant changes in nifedipine pharmacokinetics occurred in the presence of theophylline.