science

Ibutilide

Ibutilide is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ibutilide rather than just read about it. In short: Ibutilide is a Class III antiarrhythmic agent that is indicated for acute cardioconversion of atrial fibrillation and atrial flutter of a recent onset to sinus rhythm. It exerts its antiarrhythmic effect by induction of slow inward sodium current, which prolongs action potential and refractory period of myocardial cells.

Key takeaways

Ibutilide belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ibutilide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ibutilide from memory before moving on to harder problems.

Reference excerpt

Ibutilide is a Class III antiarrhythmic agent that is indicated for acute cardioconversion of atrial fibrillation and atrial flutter of a recent onset to sinus rhythm. It exerts its antiarrhythmic effect by induction of slow inward sodium current, which prolongs action potential and refractory period of myocardial cells. Because of its Class III antiarrhythmic activity, there should not be concomitant administration of Class Ia and Class III agents. Ibutilide is marketed as Corvert by Pfizer. Administration resulted in successful heart rhythm control in 31–44% of patients within 90 minutes, with sustained polymorphic ventricular tachycardia in 0.9–2.5% of patients. It appears to show better results in atrial flutter as compared to atrial fibrillation.

Mechanism of action Ibutilide, like other class III antiarrhythmic drugs, blocks delayed rectified potassium current. It does have action on the slow sodium channel and promotes the influx of sodium through these slow channels. Although potassium current seems to play a role, their interactions are complex and not well understood. Ibutilide's unique mechanism works by an activation of a specific inward sodium current, thus producing its therapeutic response in which a prolonged action potential increases myocytes’ cardiac refractoriness in case of atrial fibrillation and flutter.

Pharmacokinetics

Absorption Ibutilide is intravenously administered. It has a high first-pass metabolism, which results in a poor bioavailability when taken orally. Individual pharmacokinetic properties are highly viable during the clinical trial.

Distribution Ibutilide has a relatively large volume of distribution among individual subjects, which is about 11L/kg. Approximately 40% of the drug is bound with plasma albumin of healthy volunteers in a trial. This is also approximately close to patients with atrial fibrillation and flutter.

Metabolism Ibutilide has a high systemic plasma clearance that closes to the hepatic blood flow (29mL/min/kg). Its metabolic pathway is via liver's cytochrome P450 system by isoenzymes other than CYP3A4 and CYP2D6 by which the heptyl side chain of ibutilide is oxidized. With eight metabolites are detected in the urine, however, only one is an active metabolite that shares the similar electrophysiologic property of the Class III antiarrhythmic agents. The plasma concentration of this metabolite is only less than 10% of ibutilide.

Excretion After administration of ibutilide, it is quickly excreted by renal pathway with a half-life of approximately 6 hours. Approximately 82% of a 0.01 mg/kg dose is excreted in the urine during the trial. Among those, around 7% is excreted as unchanged drug. The remainder of the drug is excreted in feces (about 19%).

Adverse effects and contraindications Like other antiarrhythmics, ibutilide can lead to abnormal heart rhythms due to its ability to prolong the QT interval, which can lead to the potentially fatal abnormal heart rhythm known as torsades de pointes. Consequently, the drug is contraindicated in patients that are likely to develop abnormal heart rhythms; this includes individuals who have previously experienced polymorphic ventricular tachycardia, have a prolonged QT interval, sick sinus syndrome, or have recently had a myocardial infarction, among other conditions.

Patient Information

This medication will be given intravenously for your heart disease. You will have continuously ECG monitoring during the infusion and 4 hours after your infusion. Some of the minor side effects are headache and irregular heartbeat. If you experience chest pain and respiratory difficulties, you should report to your doctors immediately.

Illustrations

Worked examples

Example 1 — a first encounter with Ibutilide

Start with the simplest possible case. Write down what Ibutilide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ibutilide before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ibutilide ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ibutilide

In research: Ibutilide appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ibutilide in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ibutilide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Antiarrhythmic agents, Drugs developed by Pfizer, N-phenylmethanesulfonamide derivatives, so understanding it makes those chapters shorter.
In everyday life: Look for Ibutilide outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Ibutilide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ibutilide means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ibutilide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ibutilide in simple terms?

Why does Ibutilide matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ibutilide?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ibutilide.