Metabolites are the byproducts of a substance after it has run through your system. To determine whether you will pass or not, it is important to know how much of the illicit metabolites are in your urine and how much is tested for. Testing method and levels tested for are major factors.
Introduction Theophylline was once the cornerstone in the management of both the acute and chronic phases of reversible airway obstruction. However, it has fallen out of favor and is seldom used these days.
One Emit assay theophylline overdose may be that it has a narrow therapeutic index. Fortunately, theophylline serum levels correlate well with both therapeutic and toxic effects. The clearance of theophylline is affected by many variables which necessitate carefully individualized dosage.
Age, smoking, congestive heart failure, other diseases and drug interactions all contribute to a change in the metabolism of theophylline. These factors all necessitate dosage adjustments in order to achieve and maintain therapeutic serum levels and avoid toxicity.
So wide is the variation in clearance rates that no dose which will produce effective levels of theophylline in most patients will fail to produce toxic levels in a few. Serum theophylline measurements are essential for accurate dosage adjustment.
For these patients, small increases in doses may result in dramatic increases in serum concentrations.
Such patients have not been well characterized. Therefore, to minimize the risk of toxicity, doses of theophylline should be increased cautiously, especially at the upper levels of the therapeutic range. Monitoring Parameters An accurate and thorough patient history is essential for proper dosing of theophylline.
Take special note the following conditions: Serum theophylline level monitoring If the patient has taken a theophylline product within the previous 24 hours, obtain a level before administering any IV theophylline. Monitoring IV theophylline Obtain theophylline levels at 1, 7 and 24 hours after initiating IV therapy and every 24 hours while receiving IV theophylline.
Monitoring oral theophylline When initiating oral therapy obtain theophylline levels daily until stable. Other monitoring parameters pulse and blood pressure four times a day Signs of toxicity daily nausea, insomnia, etc.
This lower target range may be especially suited to outpatients in order to avoid potential toxicity. Precautions Adjust dosage carefully Theophylline has a relatively long half-life in certain patient populations the elderly and CHF patientsconsequently it may take several days to reach steady state.
Dosage increases should be made with caution. The patient must be followed closely for signs of toxicity. Proper serum sampling is important when monitoring oral theophylline. Suggested serum sampling times: Factors affecting theophylline elimination Hepatic disease Patients with decompensated cirrhosis, acute hepatitis, and, possible, cholestasis have reduced theophylline clearance.
A correlation between slow hepatic metabolism and serum albumin and bilirubin concentration has been made in patients with cirrhosis. Cardiac disease Patients with CHF have decreased theophylline clearance due to diminished blood flow to the liver.
With treatment of CHF, theophylline clearance increases. Fever Acute illnesses associated with fever have been reported to prolong theophylline half-life.
If fever is high and sustained, e. Diet Ingestion of a high protein, low carbohydrate diet accelerates theophylline metabolism presumably by increasing liver enzyme activity.
Dietary intake of methylxanthines, caffeine in particular, decreases theophylline metabolism by acting as a substrate for metabolizing enzymes.The molecular formula of anhydrous theophylline is C 7 H 8 N 4 O 2 with a molecular weight of Theo is available as capsules intended for oral administration, containing mg, mg, mg, or mg of anhydrous theophylline per capsule, in an extended-release formulation which allows a hour dosing interval for appropriate patients.
Enhancement of theophylline clearance by oral activated charcoal A randomized crossover trial of the effect of oral activated charcoal on the kinetics of intravenous theophylline was carried out in six normal male subjects.
After intravenous aminophylline (6 mg /kg), subjects received water or water. Lab Medicine Conference: Toxicology Studies Jim Holliman, M.D., F.A.C.E.P.
Professor of Surgery and Emergency Medicine Director, Center for International. This is relevant to an experiment I did recently finding concentrations of the drug theophylline in samples of blood serum. The therapeutic dose. The EMIT assay is performed by following a complex sequence of steps.
First a drop of urine is mixed with antibodies against the drug being sought, known quantities of the drug labeled with an enzyme, and a . After ingestion, theophylline is released from aminophylline, and theophylline relaxes the smooth muscle of the bronchial airways and pulmonary blood vessels and reduces airway responsiveness to histamine, methacholine, adenosine, and allergen.