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Digoxin Pharmacokinetics

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Digoxin pharmacokinetics the therapeutic range for digoxin range between 0.5 to 2 microgram per liter for adults and 1 to 2.6 microgram per liter for neonates most commonly the target range when treating congestive heart failure is between 0.5 to 1 microgram per liter and point 8 to 1 point 5 microgram per liter when treating arrhythmias symptoms of digoxin toxicity

Might include muscle weakness gastrointestinal complaints such as anorexia nausea vomiting abdominal pain and constipation cns side-effects such as headache insomnia confusion vertigo and changes in color vision and serious cardiovascular side effect such as 2nd or 3rd degree av block bradycardia premature ventricular contractions and ventricular tachycardia the

Primary indications for digoxin monitoring might include suspected digoxin toxicity suspected poisoning from ingestion of plants or herb all medications that contain structurally similar to glycosides impaired renal function and suspected interaction with drugs or her balls when trying to simulate blood concentration of the jackson after oral administration in

First four to six hours there will be tremendous increase in digoxin serum level but this does not reflect therapeutic nor toxicity after six hours digoxin will be distributed into tissues hands decreasing serum level for this reason there is no value of obtaining the jackson serum level unless waiting for at least six hours after oral administration in case

Of iv digoxin serum level could be taken after four hours of administration and contrast digoxin concentration in myocardium tissues does not reaches the high concentration achieved in serum as shown in the graph digoxin samples for routine plasma level monitoring should usually be obtained between 7 to 14 days following initiation or change in the maintenance

Regimen in patients with end-stage renal disease it may require from 15 to 20 days for steady-state to be achieved digoxin bioavailability differ according to formulation the bioavailability of tablets is 70% for a lexer 80% and 100% for gelatin capsules the average volume of distribution for digoxin is approximately 7.3 later burke eg volume of distribution is

Decreased in patients with renal disease hypothyroid patients and in patients taking quinidine volume of distribution is increased in hyperthyroid patients total digoxin clearance equal to digoxin metabolic clearance plus digoxin renal clearance in healthy individuals digoxin metabolic clearance has an average of 0.8 mainly per minute per kg and renal clearance

Close to creatinine clearance in patients with congestive heart failure digoxin metabolic clearance is reduced more than 50 percent to 0.33 mainly per minute per kg and renal clearance is slightly reduced by an average of 10% so we multiply creatinine clearance by both nine loading dose for digoxin can be calculated using this formula which is equal to volume of

Distribution multiplied by target serum concentration divided by salt factor x bioavailability let’s assume we would like to calculate loading doors for 70 kg patient to achieve a target serum concentration of 1.5 microgram per liter let’s assume we will use the jocks and tablets we need to apply directly into the equation where volume of distribution equal to

Seven point three later berkley g multiplied by weight which is 70 kg x cb target which is 1.5 microgram per liter divided by salt value which is 1 as the jackson is not administered as salt multiplied by bioavailability for tablets which is point seven solving this equation where all values are available will result in a loading dose of 1095 microgram which is

Very close to 1 milligram loading those administration the usual procedure is to give 50% of the loading doors initially followed by 25% after 6 hours and another 25% after another 6 hours so in our example of one milligram loading dose 50% will be given initially which is 0.5 milligram followed by boeing 2 5 milligram after 6 hours and another point 2 5 milligram

After another 6 hours from the last dose maintenance those of the jackson can be calculated using this equation which is equal to clearance of digoxin multiplied by average the jackson concentration required multiplied by tau which is the dosing interval and that’s divided by s which is the salt factor multiplied by f which is the bioavailability let’s take an

Example to calculate maintenance dose let’s assume we would like to get the maintenance dose for the same patient and assuming patient is 50 years old male with the serum creatinine concentration of 1 milligram per deciliter with target concentration of 1.5 microgram per liter serum digoxin for the treatment of chf congestive heart failure first we need to calculate

Creatinine clearance to calculate creating any clearance we will use this equation where all variables are available solving this equation would result in creatinine clearance equal to 87 point 5 milli per minute to calculate the jackson clearance we will recall our equation where total clearance of the jackson equal to metabolic clearance blasts creatinine clearance

Multiplied by buoyant line the metabolic clearance of digoxin equal to 0.33 ml per minute per kg and that’s multiplied to 70 kg the weight of the patient plus 87 point 5 the creatinine clearance multiplied by buoyant 9 and that equal to 101 point 9 ml per minute and that’s equal to one hundred forty six point seven later birthday to calculate now the maintenance

Dose we just need two blood numbers into equations where clearance equal to one hundred forty six point seven later birthday cbss average equal to one point five microgram per liter dosing interval is one day salt factor is one and bioavailability is 0.7 for tablets and that’s equal to point 3 one milligram per day since the dosage forms available either point two

Five milligram or point three seven milligram then either to give any of these forms or to give each for an alternative day which will result in those very close to oh lated maintenance those

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Digoxin Pharmacokinetics By حسين العوامي