chemistry

Halofantrine

Halofantrine 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 Halofantrine rather than just read about it. In short: Halofantrine is a drug used to treat malaria. Halofantrine's structure contains a substituted phenanthrene, and is related to the antimalarial drugs quinine and lumefantrine.

Key takeaways

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

Reference excerpt

Halofantrine is a drug used to treat malaria. Halofantrine's structure contains a substituted phenanthrene, and is related to the antimalarial drugs quinine and lumefantrine. Marketed as Halfan, halofantrine is never used to prevent malaria and its mode of action is unknown, although a crystallographic study showed that it binds to hematin in vitro, suggesting a possible mechanism of action. Halofantrine has also been shown to bind to plasmepsin, a haemoglobin degrading enzyme unique to the malarial parasites. Halofantrine was developed at SRI International for the Walter Reed Army Institute of Research from 1965 to 1975 by a team led by medicinal chemist William Colwell.

Adverse reactions Halofantrine can cause abdominal pain, diarrhoea, vomiting, rash, headache, itching and elevated liver enzymes. It can be associated with cardiotoxicity. The most dangerous side effect is cardiac arrhythmias: halofantrine causes significant QT prolongation, and this effect is seen even at standard doses. The drug should therefore not be given to patients with cardiac conduction defects and should not be combined with mefloquine. A survey from 2009 suggests that the drug is safe when correctly administered.

Other adverse reactions Consumption of grapefruit combined with certain medications can cause serious side effects, even death. Halofantrine combined with this fruit or grapefruit juice is dangerous. The mechanism of action is inhibition of CYP3A4, which is necessary to metabolize the drug and eliminate it from the body. Without CYP3A4, levels of the drug will become toxic in the body.

Pharmacology The mechanism of action of halofantrine is unknown. The absorption of halofantrine is erratic, but is increased when taken with fatty food. Because of fears of toxicity due to increased halofantrine blood levels, halofantrine should be taken on an empty stomach. Plasma levels peak at 16 hours and the half-life of the drug is about 4 days.

Uses Halofantrine is only used to treat malaria. It is not used to prevent malaria (prophylaxis) because of the risk of toxicity and unreliable absorption.

Dosing Adult dose: three doses of 500 mg six hours apart. Halofantrine should be taken on an empty stomach.

Manufacturing information and availability Halfan (GlaxoSmithKline) is available as 250 mg tablets. A full course of treatment (6 tablets) costs US$1.40 in the developing world. Halofantrine is not available in the UK or U.S.

References

Illustrations

Worked examples

Example 1 — a first encounter with Halofantrine

Start with the simplest possible case. Write down what Halofantrine 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 Halofantrine 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 Halofantrine 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 Halofantrine

In research: Halofantrine 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 Halofantrine 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: Halofantrine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Antimalarial agents, CYP2D6 inhibitors, Chloroarenes, so understanding it makes those chapters shorter.
In everyday life: Look for Halofantrine 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 Halofantrine in 20 minutes

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

Frequently asked questions

What is Halofantrine in simple terms?

Halofantrine is a drug used to treat malaria. Halofantrine's structure contains a substituted phenanthrene, and is related to the antimalarial drugs quinine and lumefantrine.

Why does Halofantrine 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 Halofantrine?

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 Halofantrine.