Anticoagulation Therapy for Stroke Prevention - Case Study Example

Anticoagulation Therapy for Stroke Prevention Appropriate anticoagulation therapy for stroke prevention The existing inconsistencies in the medicalprofession depicts different strategies of using anticoagulant as the effective strategy in managing or preventing stroke, especially in patients suffering from Atrial Fibrillation calls for an assessment of the best anticoagulant and the benefits of such in the management approach. Recent studies show that administration of low intensities of anticoagulant helps by largely reducing or elimination of risks associated with Atrial Fibrillation. Ostensibly, the main contributing factor associated with anticoagulants is the fact that this strategy is still emerging as shown by Fendrick, (2010). Besides, there are concerns that evidence-based studies reporting the clinical trials on the benefits of using anticoagulation’s may not give the desired results as reported in the literature hence the lacklustre (NICE guidelines, 2014). Besides, selection of appropriate anticoagulation therapy for stroke prevention depends on the level or mildness of the condition. Therefore, this paper examines anticoagulants incriminated for the treatment of Atrial Fibrillation in the Elderly from three perspectives: Therapeutic perspective, pharmaceutical science perspective, and pharmacy practice perspective before identifying the best anticoagulant for the current patient and recommending the appropriate dosage. Therapeutic perspective: Most anticoagulants are associated with adverse drug reactions, concerns for their duration of action, bleeding risk, and the need to carry out monitoring while adjusting dosages during the treatment period. Therefore, selection of appropriate anticoagulant for preventing Atrial Fibrillation must ensure that the practitioner considers these factors. From a therapeutic perspective, reports show that Warfarin is the first line anticoagulant for patients with Atrial Fibrillation (Nice guideline 2012), especially when the condition is primary or severe because it curbs the development of stroke. Besides, reports show that oral administration has had long-term safety for the past 50 years (AABB, 2014). In addition to that, its effect can be reversed with vitamin k antidote in case of bleeding (AABB, 2014). Moreover, warfarin has reduced rates of major gastrointestinal bleeding and myocardial infarction comparing with the novel oral anticoagulants (NHS Information Centre, 2014). Despite its complete absorption after oral administration, Warfarin is slow acting anticoagulant with a long half-life. Its two active enantiomers (R and S forms) have different therapeutic potency, metabolism, and clearance pathways (Hirsh, 2003). Besides, it has a delayed anticoagulant effect from two to 3 days while its duration of action continues for 2 to 5 days after a single dose administration (Hirsh, 2003). However, dosing of Warfarin can be described as complicated; this is due to its interaction with some foods containing vitamin K because of being displaced from serum albumin by highly bound albumin drugs (Hirsh, 2003). Therefore, periodical monitoring of international normalized ratio (INR) is necessary (Ansell, 2008). Haemorrhage risk could restrict the use of Warfarin. Therefore, using novel oral anticoagulants would be superior in term of major bleeding control. Since no monitoring required while using NOACs if the patient has good liver and kidney functions and with no signs of severe heart valves problems (Connolly, 2009). Pharmaceutical science perspective: Any novel drug must have particular specifications that require the professionals to take into consideration before prescription and administration. Inappropriate use of monitoring tools will always lead to complications or even worsen the condition it aimed to treat (NICE guidelines, 2014). Monitoring of INR within the range of 2 to 3 unit is required during Warfarin use. Any increase above that range indicates bleeding risk. It is recommended to be checked daily or on alternate days in the first week of treatment and then twice weekly for 1 to 2 weeks, afterward weekly monitoring until INR stability is attained (NICE guidelines, 2014). The international normalized ratio is calculated by dividing the prothrombin time in seconds by the mean of specific normal range; then the resulted ratio is normalised by the International Sensitivity Index (Jaffer, 2003). The serum albumin level has no significant effect on the value of INR as any elevation in the level of a free fraction of warfarin increases its renal excretion (Jaffer, 2003). However, factors that could influence the effectiveness of INR test include calibration of the instrument, the used reagent and the correct use of INR calculation (Jaffer, 2003). Moreover, some limitations of INR system related to the haemostatic disorders, concomitant illnesses, and changes in the current medications or vitamin K consumption. All these factors make INR system with a diagnostic value only if the patient is stabilised on oral anticoagulants (Palkuti, 1995; Jaffer, 2003). Recently, the point of care coagulometers has been emerged for use after many studies had proved their efficacy produced acceptable results compared with the laboratory testing (NICE guidelines, 2014). From the pharmaceutical perspective, using Warfarin as a secondary prevention in Atrial fibrillation would be effective if the patient is willing to have periodical monitoring of INR either by visiting anticoagulant clinics or by effectively using the point of care tests. Practice perspective: The recent development of the invention of alternative anticoagulants with superior therapeutic indices adds value to the strategy of preventing stroke for patients with Atrial Fibrillation. For instance, the approval of Dabigatran etexilate by the FDA, after the clinical trial and comparison with warfarin, show that the drug has a clean bill of health (Shafeeq & Tran, 2014; Spinler & Shafir, 2012). The need for anticoagulant is estimated by CHA2 DS2 -VASc score, which is counterbalanced with the score of bleeding risk that is assessed by HAS-BLED system (NICE guidelines, 2014). A man scoring one from CHA2DS2 –VASc system should take an oral anticoagulant after considering the co-morbidities, the past and current medical history, and in addition to the blood urea and electrolytes results (NICE guidelines, 2014). From pharmacy practice perspective, NOACs would be a good alternative to Warfarin if not preferred or exhibits contraindication. Dabigatran etexilate is one of NOACs, which is administered orally, given that, it is a prodrug, and it undergoes rapid conversion to an active compound, which is a direct thrombin inhibitor (Shafeeq & Tran, 2014; Spinler & Shafir, 2012). The main advantages of Dabigatran over warfarin are that they do not cause haemorrhage (Spinler & Shafir, 2012). Besides, it is less likely to interact with other drugs or even food items. The action brought by this alternative is rapid and does not require monitoring of the blood tests, which is synonymous with warfarin. Its effects are short-lived because when withdrawn, they cease to impart its effects unlike warfarin, which lasts for many days when discontinued (Spinler &Shafir, 2012). Although this drug has better features when compared with warfarin, its safety in patients with renal failure is a major concern. Therefore, the clinicians should ensure they periodically evaluate the renal function of the patients above 75 years before the administration (Spinler & Shafir, 2012). The establishment of the creatinine level to such groups of patients, especially when the levels are below 50 mL/min is necessary so that the patient is excluded from Dabigatran etexilate if they have a problem (Shafeeq & Tran, 2014; Spinler & Shafir, 2012). The other issue of dabigatran is the lack of antidote in bleeding situations when immediate intervention is required. Moreover, its short duration of action increases the risk of stroke when the patient misses the doses (Nice guideline 2012). Section two: The analysis of anticoagulants from the three perspective helps in the elucidation of the best choice for Atrial Fibrillation with the aim of preventing stroke. Therefore, the selection of appropriate anticoagulation therapy for stroke prevention for the current patient would consider a practical perspective. The warfarin has demerits because it requires intensive monitoring through the periodic testing of blood to check INR (Shafeeq & Tran, 2014). Besides, its effects continue in the patient for a longer duration after withdrawal (Shafeeq & Tran, 2014; Spinler & Shafir, 2012). However, the likelihood of warfarin to cause haemorrhage and the interaction with foods and other drugs limit its selection given that other drugs with superior properties. Upon evaluation and approval for commercialisation by the NICE and FDA, NOACs were found to possess superior properties (Nice guideline 2012). These drugs include Dabigatran etexilate, which upon comparison with warfarin was found as a better alternative (Nice guideline 2012; Shafeeq & Tran, 2014; Spinler & Shafir, 2012). Therefore, Dabigatran etexilate anticoagulant has superior properties that best suits the current patient. The usual dose for the Dabigatran etexilate in patients with Atrial Fibrillation is 150 mg, which the patient must take twice every day without or with food as shown by previous studies (Shafeeq & Tran, 2014; Spinler & Shafir, 2012). Given that our patient is nearly 80 years, using other medications like Amiodarone should be avoided to minimise bleeding risk due to Dabigatran accumulation. Therefore, the suggested dose would be 110 mg twice daily (Nice guideline 2015, BNF, 2015). Upon administering the initial dosage, it is recommended to monitor the creatinine clearance. Patients with clearance between 30 to 50 ml per minute should be given an initial dose of 75 mg and maintenance doses of 150 mg once daily (BNF,2015). The need patient assessment every three months, the assessment includes reviewing compliance record, adverse effects, thrombo embolic events, and OTC medications use (NHS Information Centre 2014). The treatment should be stopped 2 to 4 days prior any major surgery (NHS Information Centre 2014). The patient would use dabigatran as an oral anticoagulant, the withdrawal of aspirin is necessary to avoid the risk of GI bleeding (NHS Information Centre 2014). Although the patient is using ACEIs (Ramipril 10 mg once daily), which is a good option for controlling blood pressure in patient with atrial fibrillation, switching to beta blockers could give better results in controlling both of hypertension and heart rate (NHS Information Centre 2014). Moreover, beta-blockers were reported as first-line therapy for long-term rhythm control and had reduced effect for atrial fibrillation episodes (NICE guidelines 2014; Athanasios, 2012).Therefore, Atenolol 50mg daily dose would be used instead of Ramipril (Daniel 2014, BNF, 2015). When Digoxin used with Amiodarone, Digoxin dose should be reduced by 50 % to avoid digitalis toxicity that results from inhibition of both renal secretion and P-glycoprotein transporter system (Yamreudeewong, 2003). In the current patient, prescription of beta-blocker means that they no longer need Amiodarone use because this eliminates its serious side effect. Therefore, the suggestion is to maintenance a dose of digoxin at 125 micrograms per day (BNF, 2015). References List Athanasios J., Enrico A, et al, (2012) Hypertension and atrial fibrillation: diagnostic approach, prevention, and treatment. Position paper of the Working American Association of Blood Banks (24 April 2014), "Five Things Physicians and Patients Should Question", Choosing Wisely: an initiative of the ABIM Foundation (American Association of Blood Banks), retrieved 25 July 2014 Ansell J, Hirsh J, Hylek E, et al. (2008). 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