Sleep disruption in critically ill patients--pharmacological considerations

Sleep disturbances are common in critically ill patients and contribute to morbidity. Environmental factors, patient care activities and acute illness are all potential causes of disrupted sleep. Additionally, it is important to consider drug therapy as a contributing factor to this adverse experience, which patients perceive as particularly stressful. Sedative and analgesic combinations used to facilitate mechanical ventilation are among the most sleep disruptive drugs. Cardiovascular, gastric protection, anti-asthma, anti-infective, antidepressant and anticonvulsant drugs have also been reported to cause a variety of sleep disorders. Withdrawal reactions to prescribed and occasionally recreational drugs should also be considered as possible triggers for sleep disruption. Tricyclic antidepressants and benzodiazepines are commonly prescribed in the treatment of sleep disorders, but have problems with decreasing slow wave and rapid eye movement sleep phases. Newer non-benzodiazepine hypnotics offer little practical advantage. Melatonin and atypical antipsychotics require further investigation before their routine use can be recommended.

Clinical application of the Biotrack 516 system for determination of theophylline by a turbidimetric latex agglutination inhibition reaction

Several automated analytical systems for therapeutic drug monitoring (TDM) have been developed. In the present study, theophylline concentration in plasma was measured by the Biotrack 516 system for theophylline, a newly developed automated system based on the turbidimetric latex agglutination inhibition reaction, using whole blood samples obtained from 35 asthmatic patients receiving chronic theophylline therapy. The data were compared with those obtained by high-performance liquid chromatography (HPLC) and fluorescence polarization immunoassay (FPIA). Within-day and between-day precisions for the Biotrack system using blood samples obtained from nine patients ranged from 4.1 to 5.8% and from 2.0 to 6.2%, respectively. Comparison of this system with HPLC and FPIA methods indicated good correlation coefficients of > 0.960, while the respective slope and intercept did not differ from unity and zero. No cross-reactivity of this system with the main metabolites of theophylline and caffeine was observed, thus indicating that the antibodies possess specificity for theophylline. These findings suggest that the Biotrack-516 system is a method that enjoys both accuracy and precision to the same degree as established methods and hence will prove useful in the routine monitoring of plasma theophylline concentrations.

Asthma in children: emergency management

We review the pathophysiological alterations at work in asthma and outline pharmacological agents that are available for emergency therapeutic intervention, offering some general principles for management. A combined overview of predictors of outcome in asthmatic episodes in children also is presented.

The use of a rapid theophylline assay in the ambulatory setting

The Seralyzer reflectance photometer was evaluated in three ambulatory settings. Of the total 99 assays in the pediatric general medicine clinic, 47 were below the therapeutic range, and 20 patients were noncompliant. There were 13 low and nine high levels along with 22 noncompliant patients detected from a total of 109 in the allergy clinic. The physician's office documented 43 low and four high levels along with 10 noncompliant patients from 105 assays. The mean time required for Seralyzer results in both the allergy and pediatric general medicine clinic was 13 minutes. Regression analysis of both finger-stick and venipuncture split samples indicated a strong correlation between Seralyzer results and traditional methods of assay (r = 0.94 and 0.99, respectively). The Seralyzer proved accurate, timely, and simple to operate.

Comparison of two sustained-release theophylline preparations in adult patients with obstructive airways disease

The bioavailability profiles of two sustained-release oral theophylline preparations, Respbid and Theo-Dur, were compared in 19 adults with obstructive airways disease. Intravenous aminophylline was used as the reference standard. No significant differences were detected in fraction absorbed, peak-trough fluctuations, or time to peak concentrations.

The diseased lung and drugs

Among the numerous ways by which drug-lung relationships can be discussed we chose to examine three questions: Is the lung capable of directly modulating drug pharmacokinetics? Knowing that the pulmonary circulation can exert very selective and efficient clearance and catabolism of biogenic molecules such as serotonin (5-HT), norepinephrine (N.E.), prostaglandins PGE2 and PGF2 alpha, and bradykinin, as well as activation of angiotensin (A)I to AII, a similar behavior has been sought for drugs. Uptake of circulating drugs occurs clearance of biogenic amines, the significance of which remains to be fully evaluated, and iatrogenic phospholipidosis localization of which in the lung might result from the elevated drug concentration in the tissue. Lung cells contain enzymes, among them mixed function oxidases (MFO), which enables them to metabolize xenobiotics even in the intact organ. Although blood supply to the lung is higher than that to the liver, the comparatively low MFO content of the former organ predicts only a marginal pulmonary metabolic contribution in vivo. On the otherhand, enzymatic activity upon drugs can generate instable reactive metabolites which, even in minute amounts are toxic and can damage cells; furthermore, it is hypothesized that the relatively high bronchiolar Clara cell MFO content explains the striking susceptibility of the long to xenobiotics. Do lung diseases indirectly influence drug pharmacokinetics? Hindrance to blood flow is common in respiratory failure (R.F.), from both reduced area and hypoxic vasoconstriction, resulting in altered flow distribution to the liver and kidney.

Depression of theophylline elimination following BCG vaccination

This study investigated the effects of BCG vaccination on the elimination of a single dose of theophylline in twelve healthy female volunteers. Two weeks following BCG vaccination the mean serum theophylline half-life was increased significantly in subjects with a positive Mantoux test compared to the mean half-life determined prior to vaccination. The mean volume of distribution for theophylline was unchanged following vaccination. In two subjects with negative Mantoux tests theophylline half-life was unchanged after vaccination. It is therefore suggested that immunostimulation following BCG vaccination may impair the capacity of the liver to eliminate theophylline.

A difficult monitoring situation: theophylline toxicity

The author discusses the mishandling of drugs as one of the difficulties of monitoring serum theophylline levels, citing the case of a 68-year-old woman with long-standing chronic obstructive pulmonary disease, in whom the first three days of aminophylline therapy were prescribed and administered in a manner inconsistent with policy and procedure. The need for pharmacists to participate actively in clinical practice and patient care is stressed.

A practical guide to interactions involving theophylline kinetics

A practical guide to the drug interactions involving theophylline kinetics is presented. The text is classified into three categories--pharmacokinetics, pharmacodynamics, and miscellaneous drug interactions. In the discussion of pharmacokinetics, interactions are classified according to site; in vitro, intestinal, metabolic, protein binding, and renal mechanisms are considered. The pharmacodynamic section concentrates on possible additive effects of theophylline and other commonly used bronchodilators, while in the miscellaneous section, discussion is devoted to those interactions involving allergic skin testing and changed results of commonly used assay methods for theophylline. Increased awareness of possible interactions should lead to a more critical approach to theophylline prescribing, particularly in those cases where an unexpected therapeutic effect (or theophylline serum concentration) is obtained during the treatment of asthmatic patients.

Computer-simulated conversion from intravenous to sustained-release oral theophylline

A computer equipped with a pharmacokinetic program was used to theoretically determine the proper time to administer the first dose of a commonly prescribed, sustained-release oral theophylline product (Theo-Dur) in patients maintained on a continuous intravenous aminophylline infusion. Four conversion methods were tested. They included giving the first oral dose (1) immediately upon discontinuation of the iv infusion, (2) two hours after discontinuing the iv infusion, (3) four hours after discontinuing the iv infusion, and (4) two hours before discontinuing the iv infusion. Each of the four methods was simulated in three groups of patients: smokers, nonsmokers, and patients with cirrhosis. Results showed that, in most situations, given the first oral dose immediately upon discontinuation of the intravenous infusion provided minimal deviation from eventual steady-state levels. In addition, this computer simulation suggests that the initial 12-hour maintenance dose recommended by the FDA may result in toxicity in certain patient groups.