Bronchodilators

BRONCHODILATORS

BRONCHODILATORSOverview of bronchodilatorsDescription:Drugs that reverse airway constriction bronchodilation accurs with use of anticholinergic agents,adrenergic agents,and methylxanthines.A course of steroidsoften accompanies use of bronchodilators.Action:Methylxanthines relax bronchial smooth muscle by increasing cyclic adenosine monophosphate(cAMP)production through inhibitionof phosphodiesterase, an enzyme that breaksdown Camp.Indications:Relief of reversible bronchospasm associated with acute and chronic bronchial asthma,exercise induce bronchospasm,bronchitis,emphysema,bronchiectasis or other obstructive pulmonary diseases.Overview of nursing managementBecause of the CV side effects, monitor cardiopulmonary status before the start of drug therapy and periodically during therapy,paying particular attention to the presence of persistent respiratory wheezing,respiratory stridor,or continued dyspnea and tachyarrhythmias.In accordance with protocol,obtain blood samples for analysis of drug toxicity(eg,theophylline levels) to asses clients response to medication and to detect stabilization or change despite compliance with drug regimen.Assist the client to recognize and report signs of deterioratingrespiratory status(eg, use of hand-heldpeak flow meters)Teach the family and clients to recognize signs signifying possible drug toxicity(eg,nausea,vomiting,severe GI pain,irregular heart rate,restlessness,tremorsconvulsion)Evaluate the effectiveness of intervention using the following criterias:(a) the clients does not experience any deleterious effects from drug administration. (b) tissueperfusion is maintained,as evidence by improveoxygenation.Methylxanthine bronchodilatorsAre chemically related to the natural metabolite xanthine , a precursor of uric acid.they are also reffered to as the xanthines or xanthines derivatives.Because of their methyl attachments,these agents are also reffered to as methylxanthines.These agents are found as alkaloids in plant species.Pharmacodynamics /actionThe mechanism by which xanthines exert their effects and improve ventilation in cases of airway obstruction in uncertain.Although theophylline is usually classified as bronchodilator ,it actually relative weak bronchodilating effect compared with the beta against .its therapeutic action in asthma and chronic obstructive pulmonary disease (COPD) may occur by other means,such as stimulation of the ventilatory drive or direct strengthening of the diaphragm.Methylxanthine bronchodilators produce the following effects: cerebral stimulation,skeletal muscle stimulation,bronchodilation with increased vital capacity,coronary vasodilation,cardiac stimulation and diuresis.Pharmacotherapeutics/indicationSymptomatic relief or prevention of bronchial asthma and bronchospasm associated with chronic bronchitis,emphysema, and other COPD.Unlabeled use: treatment of apnea and bradycardia or prematurity(investigational only)PharmacokeneticsMethylxanthines are well absorb from oral liquids and from uncoated plain tablets.Onset varies with the type of preparation used.Maximal plasma concentrates are reached 2 hours after absorptionMetabolism is in the liver.Half-life is 3-15 hours(nonsmokers)or 4-5 hours(smokers).Excretion is in the urine.Contraindications/cautionsContra indicated in severe peptic ulcer,active gastritis,and in clients whom myocardial stimulation may prove dangerous.Used with caution in clients with acute cardiac disease,tachyarrhythmias, renal or hepatic disease,seizure disorder,hypertension,myocardial damage,glaucoma and alcoholics.interactionsDrug-drug interactionsAmphetamines,sympathomimetics:increased CNS stimulation effects of these agents.Cigarette and marijuana smoking,aminoglutethimide(adrenal steroid inhibitor),ketoconazole,phenytoin,phenobarbital.Cimetidine,erythromycin,influenza virus vaccine,oral contraceptives,troleandomycin,clindamycin,lincomycin:increase effect of methylxanthine.Sedatives:may antagonize sedative effects.

Drug-food interactionsLow-carbohydrates,high protein diet and charcoal-broiledbeef: increased effects of methylxanthines.High-carbohydrate,low-protein diet:decreased drug elimination.Food may alter: bioavailability,absorption of time-release theopylline preparations.Side/adverse effectsCNS: restlessness,diziness,insomia,muscle twitching,headache, reflex hyperexcitability,depression,speech difficulties,tonic and clonic convulsions.CV:palpitations,tachycardia,flushing,hypotension,circulatory failure.GI:nausea,vomiting,hematemesis,gastric reflux,diarrhea,intestinal bleeding,activation of ulcer pain.RENAL:diuresis,dehydration,protenuria.OTHER:tachypnea,respiratory arrest,fever,and rectal irritation.