Drugs Used for Asthma Therapy - Case Study Example

Drugs used for asthma therapy Asthma is a respiratory disease associated with the lungs and is caused by the narrowing of airways due to the result of various irritants. The narrowing is in form of inflammation, and this inflammation results in obstruction for the free flow .The complete name of this disease is Bronchial Asthma. This disease is characterized by a wheezing effect, and at times is also termed as the wheezing disease .Almost everyone is prone to it, it is caused due to the sensitivity of the bronchial reactivity (Anon., 2002). Drug chosen: Sal-butamol : An anti asthmatic drug, used for providing relief in situations of asthma and suffocation. It dilates the airways and allows ease in breathing and comfort to the asthma patients. The dose, the frequency of the dosage, as well as the maximum number of inhalations in 24 hours of the beta2 agonist should be clearly specified to the patient. The patients must directly and immediately contact the physician in case the prescribed dose of salbutamol fails in providing the comfort or causes some irritation along with. Through mouth: 4mg. for elderly and sensitive patients’ initial dose of 2mg is suggested, taken 3-4 times a day. Or at most 8mg a day is sufficient and advisable. Children under 2 years of age are provided with dose of 100 micrograms per kilogram and on average four times a day Through intramuscular injection: 500 micrograms and repeat of dose around every four hours Through aerosol inhalation: 100-200 micrograms: This in case of persistent symptoms, on average four times a day (B.N.F 2008). Through inhalation of powder: Through inhalation of nebulised solution: Nebulizer (or respirator) solutions of salbutamol and terbutaline are used for the treatment of severe acute asthma in hospital or in general practice. Patients with a severe attack of asthma should preferably have oxygen during nebulisation since beta2 agonists can increase arterial hypoxemia (Szefler & Leung, 2001). Pharmacokinetics: Pharmacokinetic characteristics of drug molecules are associated with the processes of absorption, distribution, metabolism and excretion. Salbutamol is available for administration through the following routes: Inhalation, tablet, subcutaneous injection, elixir, intramuscular injection. Pharmacokinetics of salbutamol, Bioavailability: almost constant (50 percent) Peak plasma level 2 to 3 hours Plasma half life: 3 to 5 life Active Metabolite: none: Elimination: partially Renally. Salbutamol beta 2, receptor agonist and a bronco dilator is used as an I/V per oral inhalational drug. The I/V drug is already in the circulation but the oral dosage gets re absorbed and enters into circulation. The same way inhalational drug gets reabsorbed through the lung parenchyma into circulation and reaches its target organs where it acts on the beta 2 receptors and causes bronco dilation. The excretion of the drug is renal, so an appropriate renal function is required for the appropriate pharmacokinetics of the salbutamol. Asthma has symptoms like breathlessness, wheezing, cough and chest related constraints .The asthma affected patients have sensitive airways that are prone to even the slightest of irritations from various sources. Proper care needs to be taken in this regard, and negligence can result in severe problems and in extreme cases can cause stoppage of breath and ultimately death (Polk, 1997). Pharmaco dynamics: Salbutamol is a stimulant that results in the relaxation of the smooth muscles through the increase of the intracellular cyclic adenosine mono phosphate. Salbutamol is a selective β2 agonist which mainly binds to β2 receptors at the synapse with very little binding to β1 receptors. Metabolism: Salbutamol absorbed in the gastrointestinal tract has a substantial first pass and is metabolized into Phenolic Sulfate. Excretion: Salbutamol and Phenolic Sulfate are primarily excreted via the urinary system. Adverse Reactions: An unequivocal correlation between salbutamol and dangerous asthma events has not been safely established. Salbutamol (as well as fenoterol and terbutaline) seems to cause tolerance when it is used continuously and according to several studies, it is suspected to be a co-factor in asthma deaths. It is still not clear if the latter risk is also imminent in the newer, longer-acting beta-sympathomimetic agents (formoterol, salmeterol). Inhaled salbutamol can cause tremor, inner agitation, palpitation due to sinus tachycardia, muscle cramps or headaches. These effects are more frequent following repeated use and oral administration. Particularly the high doses administered with the nebulizer and with infusions can provoke premature contractions and other ECG changes, hypokalemia or psychotic reactions. Indications: This drug has a broncho dilatatory effect on all forms of bronchial asthma. For this reason it is aptly suited to the acute treatment of bronchospasms, even in case of the severe attacks. The right amount of use is very vital for ensuring success during the treatment.  Inhalation with a nebulizer or parenteral administration is only indicated if the asthma attacks are severe. Many specialists don’t term them safe for long term use, and believe they can have negative repercussions in case of extensive use of a large period of time. This drug can also be used in infusions for the prevention of premature labor at the end of pregnancy and for the therapy of hyperkalemia. Vulnerable groups: Pregnant Women: Inhalation is allowed during the entire pregnancy stage. During the treatment of potential premature birth tachycardia is dose limiting. Children: it is quite difficult for the young children to use metered dose aerosols. Use of nebulizer is recommended, inhalation aids (spacer) or powder inhalers are also recommended: when needed 3 to 4 daily inhalations of 100 to 200 µg. Maybe, even oral administration (syrup, single dose 1-2 mg). Contraindications: Salbutamol must not be used to prevent premature labour in the case of a pre-eclampsia, placenta previa or bleedings. Chlorofluorocarbon propellants used in some aerosol inhalers can produce cardiac arrhythmias and sensitize the heart to adrenalin induced arrhythmias. Nursing Mothers: Possibly eliminated in form of breast milk. No common and known problems are reported for the neonate. Elderly people: There are more side-effects (especially cardiovascular) in the elderly. Inhalation aids (spacer) or powder inhalers are often useful. Renal failure:  No particular cautionary measures necessary Liver Insufficiency: No particular cautionary measures necessary. Side effects: Salbutamol can have various side effects, a serious threat that is being noticed as a side effect of this drug is “Hypokalaemia”. Extra care and caution is needed in cases of severe asthma, since this effect may be potentiated by concomitant treatment with theophylline and its derivatives are corticosteroids, and diuretics. Plasma-potassium concentration needs to be kept in check and monitored on a regular basis in case of severe asthma in order to prevent any serious losses and problems. Various other side effects of salbutamol include muscle cramp, headache ,palpitation , tachycardia, arrhythmias, peripheral vasodilatation, myocardial ischemia, and disturbances of sleep and behavior, other side effects may include Paradoxical bronchospasm, urticaria, angioedema , hypotension, and collapse. All these side effects have been noticed in various asthma patients over periods of time, and all of them are equally dangerous and threatening and cannot be ignored. Increased risk of cardiovascular stroke: When parental salbutamol is given with atomoxetine, it possibly reduces plasma concentration of digoxin (Aronson, 2012). Caution: Salbutamol should be used with caution in hyperthyroidism, cardiovascular disease, arrhythmias, susceptibility to QT-interval prolongation, and hypertension. If additional doses are needed during pregnancy, they should be given by inhalation because a parenteral beta2 agonist (salbutamol) can affect the myometrium in an adverse manner. Accurate and repeated instructions for the use of the metered dose aerosol or of the spacer and for self-monitoring with the peak flow meter are indicated. There may be increased muscular performance after the inhalation of salbutamol (is not considered doping yet). For diabetes patients extra care should be taken and the drug should be taken only after the prescription of a physician. Element of addiction: The drug can prove addictive in nature, therefore, like any other drug, is not recommended for long use or intensive use during the dosage, a balance in intake must be taken, patients provided with a selective beta2 agonist injection for severe attacks should be advised to attend hospital immediately after using the injection, for further assessment. Beta2 agonists may also be given by intramuscular injection (Page & Barnes, 2004). References: Aronson, J. K., 2012. Side Effects of Drugs Annual: A Worldwide Yearly Survey of New Data in Adverse Drug Reactions. 33 ed. s.l.:Elsevier. Britain, R. P. S. o. G., 2008. British National Formulary. 56 ed. s.l.:BMJ Group and RPS Publishing. Info parents-Asthma Definition. (2002). Retrieved 2012 йил 7th-Mar from http://www.respirar.org/eng/infoparents/pdf/asthmadefinition.pdf Mann, J. (2000). Murder, magic and medicine. Oxford University Press. Page, C. P. & Barnes, P. J., 2004. Pharmacology and therapeutics of asthma and COPD. s.l.:Springer. Plaut, T. F., & Jones, T. B. (1999). Dr. Tom Plauts asthma guide for people of all ages. Pedipress, Inc. Polk, I. J., 1997. All about asthma: stop suffering and start living. s.l.:Insight Books, Plenum Press. Szefler, S. J., & Leung, D. Y. (2001). Severe asthma: pathogenesis and clinical management. CRC Press. Read More