Xanthine bronchodilators

Serious overdose with this xanthine bronchodilator can provoke serious hypotension, cardiac arrhythmias, and convulsions. These symptoms indicate a poor prognosis, particularly in elderly patients. Symptoms of poisoning after a high dose of a slow-release preparation can be delayed for several hours as the drug gradually accumulates to toxic concentrations. Patients with plasma concentrations greater than 60 Lig/ml may require charcoal haemo-perfusion. 

Formulations of xanthines include intravenous injection, tablets and capsules. Examples of xanthine bronchodilators are theophylline and aminophylline. 

Which information should the nurse discuss with the client diagnosed with reactive airway disease who is prescribed theophylline (Slo-Phyllin), a xanthine bronchodilator ... 

Apart from these few reports, the literature appears to be otherwise silent about an interaction between the MAOIs and xanthines. Whether this reflects their mildness and unimportance, or their rarity, is not clear. There would seem to be no need for any special precautions in patients taking MAOIs who are given xanthine bronchodilators or consuming caffeine-containing heverages or pharmaceuticals, but bear these adverse reports in mind in the event of any unexpected response. Nevertheless, some manufacturers of MAOIs recommend the avoidance of excessive amounts of tea and coffee, or caffeine in any form. " ... 

The modern usage of P2" go Asts for the treatment of asthma dates to 1903 when the effect of injected epinephrine [51-43-4] (adrenaline) C2H23NO2, (1 R = CH3) was investigated (see Epinephrine and norepinephrine) (33). As in some other modem treatments, eg, xanthines and anticholinergics, the roots of P2" go Ast therapy for asthma can be found in historical records which document the use of herbal extracts containing ephedrine [299-42-3] C qH NO, (2) as bronchodilators. Epinephrine and ephedrine are stmcturaHy related to the catecholamine norepinephrine [51-41-2] CgH NO, (1, R = H), a neurotransmitter of the adrenergic nervous system (see Neuroregulators). 

The bronchodilating effect of caffeine has been recognized for hundreds of years. In the western world the first description of a caffeine preparation for asthma was made in 1859 (59) by a Scottish physician who recommended strong black coffee as a bronchodilator. In many parts of the world, however, use of xanthines is less frequent than in the United States. 

Initially, it was beheved that the abiUty of xanthines phosphodiesterase (PDF) led to bronchodilation (Fig. 2). One significant flaw in this proposal is that the concentration of theophylline needed to significantly inhibit PDE in vitro is higher than the therapeutically useful semm values (72). It is possible that concentration of theophylline in airways smooth muscle occurs, but there is no support for this idea from tissue distribution studies. Furthermore, other potent PDE inhibitors such as dipyridamole [58-32-2] are not bronchodilators (73). EinaHy, although clinical studies have shown that neither po nor continuous iv theophylline has a direct effect on circulating cycHc AMP levels (74,75), one study has shown that iv theophylline significant potentiates the increase in cycHc AMP levels induced by isoproterenol (74). 

Examples of the xanthine derivatives (drag that stimulate the central nervous system [CNS] resulting in bronchodilation, also called methylxanthines) are theophylline and aminophylline. Additional information concerning the xanthine derivatives is found in the Summary Drag Table Bronchodilators. 

The xanthine derivatives, although a different class of drag, also have bronchodilating activity by means of their direct relaxation of tlie smooth muscles of the bronchi. 

In the clinical area, the largest share of analytical methods development and publication has centered on the determination of theophylline in various body fluids, since theophylline is used as a bronchodilator in asthma. Monitoring serum theophylline levels is much more helpful than monitoring dosage levels.44 Interest in the assay of other methylxanthines and their metabolites has been on the increase, as evidenced by the citations in the literature with a focus on the analysis of various xanthines and methylxanthines. 

AminophyUine [Bronchodilator/Xanthine Derivative] Uses Asthma, COPD bronchospasm Action Relaxes smooth muscle (bronchi, pulm... 

This xanthine derivative is an only a modest bron-chodilator in COPD, and because of its narrow therapeutic range, frequently seen adverse effect and drug interactions, it is becoming less frequently used, some patients experience side effects even within the therapeutic range. The non-bronchodilator effects of theophylline such as systemic and pulmonary vascular dilatation, central nervous system stimulation, improvement of the strength and effectiveness of respiratory muscles and possibly anti-inflammatory effects are of disputed clinical significance at usual therapeutic levels. 

Mechanism of Action A xanthine derivative that acts as a bronchodilator by directly relaxing smooth muscle of the bronchial airways and pulmonary blood vessels. Therapeutic Effect Relieves bronchospasm and increases vital capacity. Pharmacokinetics Rapidly and well absorbed. Protein binding Moderate (to albumin). Extensively metabolized in liver. Partially excreted in urine. Half-life 6-12 hr (varies). 

Of the xanthines, theophylline is the most effective bronchodilator, and it has been shown repeatedly both to relieve airflow obstruction in acute asthma and to reduce the severity of symptoms and time lost from work or school in patients with chronic asthma. Theophylline base is only slightly soluble in water, so it has been administered as several salts containing varying amounts of theophylline base. Most preparations are well absorbed from the gastrointestinal tract, but absorption of rectal suppositories is unreliable. 

Metaproterenol (Alupent, Metaprel) [Bronchodilator/ Beta-Adrenergic Agonist] Uses Asthma reversible bronchospasm Action Sympathomimetic bronchodilator Dose Adults. Neb 0.2-0.3 mL in 2.5-3.0 mL of NS Peds. Neb 0.1-0.2 mL/kg of a 5% soln in 2.5 mL NS Caution [C, /-] Contra Tach, other arrhythmias Disp Aerosol 0.65 mg/inhal soln for inhal 0.4, 0.6% tabs 10, 20 mg syrup 10 mg/5 mL SE Nervousness, tremors (common), tach, HTN Interactions T Effects W/ sympathomimetic drugs, xanthines T risk of arrhythmias W/ cardiac glycosides, halothane, levodopa, theophylline, thyroid hormones T HTN W/ MAOIs effects W/ BBs EMS Separate additional aerosol use by 5 min fewer 3i effects than isoproterenol longer-acting monitor lung sounds before/after administration... 

Xanthine derivatives are a group of chemically similar compounds that exert a variety of pharmacologic effects. Common xanthine derivatives include theophylline, caffeine, and theobromine (Fig. 26-2) these compounds are frequently found in various foods and beverages (tea, coffee, soft drinks). Theophylline and several theophylline derivatives are also administered therapeutically to produce bronchodilation in asthma and other forms of reversible airway obstruction (bronchitis, emphysema).65,79 Theophylline and caffeine are also potent CNS stimulants, and some of the more common side effects of these drugs are related to this CNS excitation (see Adverse Side Effects, later in this chapter). 

Bronchodilators [xanthine derivatives] -phylline Theophylline, aminophylline Bronchodilation (26)... 

With HPLC, serum concentrations of this important bronchodilator can be determined in about 10 min on approximately 5 p,L of serum, allowing quick dosage adjustment to ensure therapeutic levels while avoiding toxicity. In addition, LC eliminates the need for extraction procedures and prevents interference from metabolites, other medications, and dietary xanthines such as caffeine. Using an internal standard, the technician can obtain... 

Q10 Other bronchodilator agents include nebulized ipratropium. Ipratropium is a muscarinic receptor antagonist that helps to relax bronchial smooth muscle which has contracted via parasympathetic stimulation. The xanthines theophylline and aminophylline (theophylline ethylenediamine) are alternative bronchodilator agents. These agents may act as phosphodiesterase inhibitors and, although they have been used as bronchodilators for many years, adverse CNS, GI and cardiovascular effects may limit their usefulness. 

ADENOSINE BRONCHODILATORS -THEOPHYLLINE 1 efficacy of adenosine Theophylline and other xanthines are adenosine receptor antagonists Watch for poor response to adenosine higher doses may be required... 

PENTOXIFYLLINE BRONCHODILATORS- THEOPHYLLINE Possibly t theophylline levels Uncertain possibly competitive inhibition of theophylline metabolism (pentoxifylline is also a xanthine derivative) Warn patients of the possibility of adverse effects of theophylline monitor levels if necessaiy... 

ALLOPURINOL BRONCHODILATORS -THEOPHYLLINE t theophylline levels Allopurinol inhibits xanthine oxidase Watch for early features of toxicity of theophylline (headache, nausea)... 

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