Kinetics and efficacy of theophylline in the treatment of apnea in the premature newborn

Aminophylline (theophylline-ethylenediamine) was administered to 27 premature newborns to prevent apneic spells. Of the 22 patients monitored for theophylline concentration, a therapeutic blood level was reached in 19 in 1--2 days, and 3 stayed below it. "Toxic" blood levels (less than or equal to 20 microgram/ml) were reached in 3 cases, one of whom showed signs of toxicity. Theophylline treatment was not efficient in the prevention of apnea when a serious underlying disease was present. Theophylline blood half-life (mean:27.0 h) and clearance (mean 12.9 ml/h/kg) confirmed the slow elimination pattern of the drug in the premature infant.

Plasma concentrations of diazepam, noradiazepam and amylobarbitone after short-term treatment of anxious patients

Twenty-four anxious inpatients were treated with diazepam, amylobarbitone and placebo, each given in flexible dosage for one week, according to a fully-balanced design. Plasma concentrations of diazepam and of its metabolite nordiazepam and of amylobarbitone were determined after two, four and seven days of treatment. Clinical and psychological assessments were made after seven days of each treatment by means of psychiatrist rating scales, patient's self-rating and a comprehensive battery of performance measures. Diazepam and nordiazepam but not amylobarbitone were accumulating over the seven days of treatment. In patients on diazepam without previous amylobarbitone, nordiazepam accumulated more rapidly than diazepam over the week so that the ratio of diazepam to nordiazepam was 2.21 after two days but only 1.14 after seven days; those with previous amylobarbitone on the other hand always had nordiazepam concentrations higher than those of the administered drug and both were accumulating equally. Diazepam and nordiazepam were still detectable in most patients two weeks after the interruption of treatment. No correlations were found between drug concentrations and clinical and psychological effects.

Clinical pharmacokinetics of diazepam

Diazepam is still one of the most used of the benzodiazepine group of drugs. Extensive studies over 10 years have defined a fairly complete profile of its kinetics. Minor aspects relating to patterns of its metabolism and excretion in certain age groups and in some disease states remain to be described quantitatively. However, there is more than sufficient kinetic information available for the requirements of good clinical practice. For optimum clinical benefit with minimum side-effects the following kinetic properties should be borne in mind: (a) there is a large interindividual variation (up to 30-fold) in dose/blood level ratios, especially when treatment is short-term; (b) the elimination half-life is prolonged in the elderly and the newborn and in some cases of liver disease; (c) there is accumulation of the active N-desmethylated metabolite during long-term treatment; and (d) administration of diazepam to pregnant women leads to rapid distribution from the maternal to fetal compartment: accumulation of both diazepam and desmethyldiazepam could cause prolonged sedation in the newborn. As there does not appear to be any clear relationship between the concentration of diazepam in the plasma and clinical effect, measurement of blood levels, other than for research purposes, is unnecessary. Based on kinetic data, a single administration of diazepam at night should be adequate for hypnotic and anxiolytic effects in most patients.

Distribution of fenfluramine in normal and obese mice

Concentrations of fenfluramine and its metabolite, norfenfluramine, were measured in blood, brain and parametrial adipose tissues 15, 30, 60 and 120 min after intraperitoneal (i.p.) administration of fenfluramine hydrochloride (10 mg/kg) to normal and gold-thioglucose obese mice. Concentrations of fenfluramine were higher in the brain of obese mice than in normal mice, while there was no difference in norfenfluramine levels in the two groups. This difference may be related to higher blood levels of fenfluramine but not of norfenfluramine in obese animals. The drug was presented in about the same concentrations in the adipose tissue of the two groups. These results may explain previous findings that fenfluramine was more effective as an anorectic agent in obese than in lean mice.

Human pharmacokinetics and bioavailability of temazepam administered in soft gelatin capsules

Plasma levels of temazepam were determined in healthy subjects after single oral administration of soft and hard gelatin capsules, and after 7 consecutive night-time doses in soft capsules. Absorption from soft gelatin capsules was significantly faster and produced earlier and higher peak plasma levels. The two pharmaceutical forms did not show any significant difference in relative availability. The apparent half-life of temazepam after night-time administration was significantly shorter than after morning administration, but no change in half-life was observed between the first and seventh night-time doses.

Bioavailability and platelet aggregation inhibitory activity of solufenum. A comparison with ibuprofen

Bioavailability and platelet aggregation inhibitory activity of the lysine salt of ibuprofen (solufenum) were compared with those of the parent molecule in 5 healthy male volunteers. The study had a randomized, cross-over design. The average peak plasma level and the area under the curve were higher when solufenum was administered orally as compared to the same preparation given i.m. or as compared to oral ibuprofen. However, the bioavailability of the 3 preparations studied was not significantly different. In contrast, the inhibitory effect on adrenaline-induced platelet aggregation appeared significantly different. In contrast, the inhibitory effect on adrenaline-induced platelet aggregation appeared significantly earlier after the administration of both solufenum than after ibuprofen. The clinical relevance of these findings is discussed.

Plasma levels of di-no-propylacetate and clonazepam in epileptic patients

Plasma levels of DPA and CNP and associated antiepileptic drugs were measured in groups of respectively 106 and 30 epileptic patients aged from 3 to 49 years. A poor correlation between daily oral dose and plasma levels of both drug was observed when the whole group of patients was considered. A better correlation was seen in a group of adult patients who received DPA and PB. Children below 10 years of age disposed both drugs faster than adults and the difference was significant (p less than 0.01) in groups receiving PB as associated drug. Patients medicated with PB and DPA or CNP showed lower plasma levels of both drugs; on the other hand DPA appeared to cause a decrease of PB clearance which was more marked in children. The clinical significance of the fluctuations of daily plasma levels of both drugs are discussed in relationship to the schedule of administration and plasma sampling. Observations on the therapeutic ranges and adverse effect of the drugs are reported.

Regional distribution of diazepam and its metabolites in the brain of cat after chronic treatment

Repeated administration of diazepam leads to remarkable accumulation of N-desmethyldiazepam in white matter structures and in subcortical areas such as thalamus, hypothalamus, and hypophysis. Diazepam and the hydroxylated metabolites were present in lesser amounts. The distribution pattern of diazepam and N-desmethyldiazepam offers a rationale for its efficacy in inhibiting seizures spreading and for the lack of effect on primary foci discharges.

An integrated approach for the evaluation of psychotropic drug in man. I. Studies on amphetamine. Relationship between drug levels and psychophysiological measurements

Following an integrated approach based on the contemporary recording of drug plasma levels, central (CNS) and peripheral responses and performance tests, the effects of two different amphetamine formulations were evaluated in healthy volunteers. Interesting relationships were observed between amphetamine initial rate of entry into the blood stream and both incidence of side effects (S.E.) and rise in arterial blood pressure. Minimal thresholds for CNS (5 ng/ml) and peripheral (20 ng/ml) effects could also be determined. It appeared also that the personality of the subject may have some bearing on both incidence of side effects and performance. The described methodology seems valuable in valuating psychotropic drug effects in man through a comprehensive integrated approach.

Pharmacokinetics of N-demethyldiazepam in patients suffering from insomnia and treated with nortriptyline

1 Hospitalized patients suffering from insomnia were treated with N-demethyldiazepam (30 mg p.o.) for 10 days, while continuing treatment with nortriptyline (75 or 100 mg daily). 2 Clinical evaluation performed by objective rating scales showed a positive therapeutic effect. No correlation was found however between drug plasma levels and clinical efficacy. A high inter-individual variability was observed. 3 In three cases the N-demethyldiazepam disappearance curve showed a biexponential decay, with a slow first component followed by a faster one. 4 Compared with diazepam the tested drug has a longer plasma apparent half-life and a lower relative clearance.

Placental transfer to diazepam and its disposition in the newborn

Diazepam (DZ) placental transfer in pregnant women at term, following single or repeated drug administration by various routes, was evaluated. DZ and its metabolite N-demethyldiazepam (NDZ) were constantly present in umbilical cord plasma at concentrations comparable to the mother's shortly after drug administration. N-methyloxazepam (MOX) was detected in cord plasma only in a limited number of cases following chronic DZ treatment. Postmortem analysis of fetal tissue concentrations showed accumulation of NDZ in heart and lungs. Differences in NDZ concentrations between venous cord (VC) and arterial cord (AC) plasms suggest metabolic degradation of DZ in the fetus. The DZ apparent plasma half-life in the newborn was found to be longer (31 plus or minus 2 hr) than previously observed in infants and children. The low drug clearance appears to be linked to reduced urinary excretion of hydroxylated metabolites, suggesting limited capability to dispose of DZ in the newborn.

N-desmethyldiazepam and amylobarbitone sodium as hypnotics in anxious patients. Plasma levels, clinical efficacy and residual effects

Drug plasma levels of N-desmethyldiazepam (10 and 20 mg/day given at night) and amylobarbitone sodium (200 mg/day given at night) were determined in 45 patients after 1 and 7 days of treatment together with estimates of hypnotic and residual effects. No relationships were found between clinical rati ngs of hypnotic effect and drug plasma levels, while significant correlations were observed between some performance taska and drug plasma concentrations of amylobarbitone sodium, and of the higher dose of N-desmethyldiazepam.

Differential effects of amphetamine, fenfluramine and norfenfluramine stereoisomers on the increase of striatum homovanillic acid in rats

(+)-Amphetamine is more effective in increasing the concentration of striatum homovanillic acid (HVA) in rats than the (-)-isomer while the (-)-isomers of fenfluramine and norfenfluramine are more active than their (+)-isomers. The concentrations of the drugs in the striatum do not explain the difference observed between the isomers on striatum HVA. Fenfluramine does not appear to act on striatum HVA through the formation of norfenfluramine.