Use Of Foxglove In Heart Disorders Biology Essay

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The digitalis is usually a biennial plant, however it is some times a annual or perennial, this is different from species to species. It has a thick, rounded, fuzzy stem that can grow as tall as two yards. The first years growth, the leaves are in a thick rosette shape. These leaves war wooly, veined and have a bitter taste. Flowers usually grow in the first or second year, again dependent on the species. The flowers are bell-shaped and can grow to about three inches long. The flower color can be many different colors ("Digitalis," 2009).

The chemical that we are interested in is called cardiac glycoside. In particular it is called digoxin (Cavet). This is from the species Digitalis lanata leaves. This cardiac glycoside is extracted from the second year's leaf growth (Weiler). Digoxin contains a hydroxyl group at the C-3 position and the B-ring next to the pentane. It also contains a lactone and a triple-repeating sugar which is called the glycoside(Jeffrey et al., 1993).

Digitalis glycosides are used for congestive heart failure (Califf) and arrhythmia (Doherty), particularly atrial tachycardia and atrial fibrillation (Jordaens).

Congestive heart failure is when the heart is unable to maintain proper blood circulation in of the blood to all the body tissues. It also has to do with the failure to be able to pump out the blood that just returned by the veins (congestive heart failure).

Arrhythmia is when there is an alteration in the rhythm of the heartbeat. This can be either the timing of the beat or the force it pumps (arrhythmia).

Atrial fibrillation is when there is a very rapid and uncoordinated contractions of the atria of the heart. This results in a lack of ordination between the pulse and the heartbeat (atrial fibrillation).

Atrial tachycardia (a type of supraventricular tachycardia) can also be helped with this drug. This means that some structure above the ventricular (the atrium) is beating faster than it should be. It is cause by the lack of direct involvement from the AV node (Budzikowski).

Mechanism of drug action

The mode of action of Digitalis is by inhibiting sodium-potassium ATPase. This increases intracellular concentration of sodium. This causes an increase intracellular calcium by decreasing passively the action of the sodium-calcium exchange pump in the sarcoplasmic reticulum (Hansen, Gervais). It also has a effects the parasympathetic nervous system. Because of this it is used in cardiac arrhythmias during atrial fibrillation(Watanabe).

It should be noted that Digitalis is very toxic. It is cause from an overdose of any part of the plant. This can cause anorexia, nausea, vomiting and diarrhea and jaundice. Bradycardia also occurs. This could cause death(Smith, Soldin).

Comparison with conventional therapy/synthetic drugs

The therapeutic use of this foxglove is very narrow. If one was to dose the leaf for therapy, it would be 1.5 grams of the leaf divided between two daily doses. However, since it is very dangers, one would require close doctors supervision. When we compare this with the purified digoxin, it is usually used at 0.125 to 0.25 milligrams per day (Hood, Dec).

Following is a brief comparison between the different medications that are conventionally used. Angiotensin-converting-enzyme (ACE) inhibitors are the drug therapy first line of defense. It slows the progression of heart failure. It also acts as a vasodilator, which lowers blood pressure and reduces the workload on the heart. It also helps the body prevent the creation of angiotensin. Angiotensin causes a rise of blood pressure because of the tightening of the blood vessels (Flather).

Diuretics are used for people who have swelling in their tissues caused by fluid buildup. It causes the kidneys to remove more water and sodium from the blood. The end result is that the heart's workload is decreased because there is less less fluid that needs to be pumped(Faris). However, digoxin, as we know, increases the force of contractions in the heart. It relieves heart failure symptoms. Digoxin is especially used a lot when ACE inhibitors and diuretics are not working(Klabunde, 2010).

Beta blockers help reduce the heart's reaction to more fluid to beat faster. It acts on a specific receptor, the beta receptor, on the heart. This reduces the chemical signals that increase heart rate. This slows the heart and lowers blood pressure. It is sometimes used with other drugs like diuretics, ACE inhibitors and digoxin in heart failure(Klabunde, 2010).

Blood clots can form in blood vessels of people with heart failure. Warfarin is some times given to thin the blood. This helps prevent strokes (Reitsma).

Then next two drugs effect the different mechanisms that regulate heart rate. Angiotensin II receptor blockers prevent the angiotensin II from rising. This helps prevent this chemical from having any effects on the heart and blood vessels, in turn helps keep the blood pressure form rising(Klabunde, 2010). However, calcium channel blockers help interfere with calcium's role in helping the muscles of the heart contract. This helps decrease high blood pressure and improves the blood circulation in the heart(Klabunde, 2010).

Lastly, potassium is sometimes given to help control the rhythm of the heart. This helps the heart because it helps make sure there that the nervous system and the heart muscles are working correctly(Croxson).

It also must be noted that there are a number of drug interactions with digoxin. This should be taken seriously because some are deadly. Elevation of digoxon serum levels interacting with some drugs such as amiodarone, erythromycin, cyclosporine, etc. or electrolyte imbalances can cause this deadly interaction (Tatro).

Therapeutic promise of phytochemical

Foxglove extract digoxin is indicated in patients with current or prior symptoms of hart failure (stage C). This helps decrease the risk of hospitalization. [Hunt]

This plant chemical can be used for issues including positive inotropic effect, slowing of rapid ventricular rate, vasodilation of peripheral vessels, increasing baroreceptor (sensors located in the blood vessels) sensitivity, reducing plasma neurohormones, increasing vagal tone and diuresis. Many of these conditions were discussed before above. [Rahimtoola]

There are many benefits in including this drug in a regimen for someone who has heart failure. It can be taken by mouth only once a day. It is usual well tolerated by patients. Also it is relatively inexpensive which means that there is a reduction in the treatment of heart failure. [Ahmed].�

Also there is other beneficial effects such as symptomatic improvement, improved heart failure score, increased exercise capacity and VO2, improved hemodynamics at rest and on exercise, increased LVEF (left ventricular ejection fraction) at rest and on exercise and reduction of heart rate ("Cardiovascular diseases ," 2010).

On the down side and as already mentioned, digoxin and foxglove are both toxic at a certain quantity. Digoxin is limited to a narrow therapeutic range of 0.5-1 ng/mL. A greater dose of digoxin or this drug being used with certain other drugs can lead to digoxin intoxication. This means that if one is on digoxin one most be closely monitored. [Gheorghiade], ("Cardiovascular diseases ," 2010).

Conclusion

The use of foxglove and it's derivative, digoxin, has been used and researched for a number of years going back to the 18th century. The drug digoxin comes from the leaves of the species Digitalis lanata. Digoxin is made up of the chemical called a cardiac glycoside.

Digoxin is used for congestive heart failure and arrhythmias. It increases the force of heart contractions and relieves heart failure symptoms. Digoxin is especially useful for individuals who are not reacting to ACE inhibitors and diuretics in a positive way.

Digoxin is a very effective and low cost drug. Many people are able to tolerate it and decreases hospital stays.

However, as noted several times already, there is a concern for toxicity. If one takes the the herb or the processed drug, one needs to be under a physician�s supervision.

If one would like to take the natural route and use the leaf therapy, one needs to take 1.5 grams of the leaf divided between two daily doses. However, this is not to say that one should take this without a doctor's supervision. This quantity compared to purified digoxin, it is about 0.125 to 0.25 milligrams per day.

Overall this herb is still used in medicine a lot because it is so useful. However, one has to be very careful with it since its therapeutic dose is so close to its toxic dose.

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