chemistry

Penbutolol

Penbutolol is a chemistry 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 Penbutolol rather than just read about it. In short: Penbutolol (brand names Levatol, Levatolol, Lobeta, Paginol, Hostabloc, Betapressin) is a medication in the class of beta blockers, used in the treatment of high blood pressure. Penbutolol is able to bind to both beta-1 adrenergic receptors and beta-2 adrenergic receptors (the two subtypes), thus making it a non-selective β blocker.

Key takeaways

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

Reference excerpt

Penbutolol (brand names Levatol, Levatolol, Lobeta, Paginol, Hostabloc, Betapressin) is a medication in the class of beta blockers, used in the treatment of high blood pressure. Penbutolol is able to bind to both beta-1 adrenergic receptors and beta-2 adrenergic receptors (the two subtypes), thus making it a non-selective β blocker. Penbutolol is a sympathomimetic drug with properties allowing it to act as a partial agonist at β adrenergic receptors. It was approved by the FDA in 1987 and was withdrawn from the US market by January 2015.

Medical uses Penbutolol is used to treat mild to moderate high blood pressure. Like other beta blockers it is not a first line treatment for this indication. It should not be used or only used with caution in people with heart failure and people with asthma. It may mask signs of low blood sugar in people with diabetes and it may mask signs of hyperthyroidism. Animal studies showed some signs of potential trouble for women who are pregnant, and it has not been tested in women who are pregnant. It is not known if penbutolol is secreted in breast milk.

Side effects Penbutolol has a low frequency of side effects. These side effects include dizziness, light headedness, and nausea.

Pharmacology

Pharmacodynamics Penbutolol is able to bind to both beta-1 adrenergic receptors and beta-2 adrenergic receptors (the two subtypes), thus making it a non-selective β blocker. Penbutolol is a sympathomimetic drug with properties allowing it to act as a partial agonist at β adrenergic receptors. Blocking β adrenergic receptors decreases the heart rate and cardiac output to lower arterial blood pressure. β blockers also decrease renin levels, which ultimately results in less water being reabsorbed by the kidneys and therefore a lower blood volume and blood pressure. Penbutolol acts on the β1 adrenergic receptors in both the heart and the kidney. When β1 receptors are activated by a catecholamine, they stimulate a coupled G protein which activates adenylyl to convert adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP). The increase in cAMP ultimately alters the movement of calcium ions in heart muscle and increases heart rate. Penbutolol blocks this and decreases heart rate, which lowers blood pressure. The ability of penbutolol to act as a partial agonist proves useful in the prevention of bradycardia as a result of decreasing the heart rate excessively. Penbutolol binding β1 adrenergic receptors also alters kidney functions. Under normal physiological conditions, the enzyme renin converts angiotensinogen to angiotensin I, which will then be converted to angiotensin II. Angiotensin II stimulates the release of aldosterone from the adrenal gland, causing a decrease in electrolyte and water retention, ultimately increasing water excretion and decreasing blood volume and pressure. Like propranolol and pindolol, it is a serotonin 5-HT1A and 5-HT1B receptor antagonist; this discovery by several groups in the 1980s generated excitement among those doing research on the serotonin system as such antagonists were rare at that time.

Pharmacokinetics Penbutolol is rapidly absorbed from the gastrointestinal tract, has a bioavailability over 90%, and has a rapid onset of effect. Penbutolol has a half life of five hours.

Chemistry The experimental log P of penbutolol is 4.15. Penbutolol showed the second highest predicted lipophilicity of 30 clinically relevant beta blockers, with the most lipophilic beta blocker predicted to be the lesser-known bopindolol.

Society and culture

Availability Penbutolol was approved by the FDA in 1987. In January 2015 the FDA acknowledged that the penbutolol was no longer marketed in the US, and determined that the drug was not withdrawn for safety reasons.

References

Illustrations

Worked examples

Example 1 — a first encounter with Penbutolol

Start with the simplest possible case. Write down what Penbutolol claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 Penbutolol 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 Penbutolol 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 Penbutolol

In research: Penbutolol appears in chemistry 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 Penbutolol 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: Penbutolol is common in secondary-school and first-year university syllabi. It links to neighbouring topics 5-HT1A antagonists, 5-HT1B antagonists, Beta blockers, so understanding it makes those chapters shorter.
In everyday life: Look for Penbutolol 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 Penbutolol in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Penbutolol 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 Penbutolol out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Penbutolol in simple terms?

Why does Penbutolol matter?

Because it connects several chemistry 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 Penbutolol?

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 Penbutolol.