Mepacrine

Key takeaways

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

Reference excerpt

Mepacrine, also called quinacrine or by the trade names Atabrine or Atebrin, is a medication with several uses. It is related to chloroquine and mefloquine. Although available from compounding pharmacies, as of August 2020 approved formulations are not available in the United States.

Medical uses

The main uses of mepacrine are as an antiprotozoal, antirheumatic, and an intrapleural sclerosing agent. Mepacrine finds off-label use as a primary antimicrobial agent for patients with metronidazole-resistant giardiasis and patients who should not receive or cannot tolerate metronidazole. Giardiasis with a high level of drug resistance may even require a combination of mepacrine and metronidazole to cure. Mepacrine is also used off-label for the treatment of systemic lupus erythematosus, indicated in the treatment of discoid and subcutaneous lupus manifestations, particularly in patients who are unable to take hydroxychloroquine. As an sclerosing agent, it is used as pneumothorax prophylaxis in patients at high risk of recurrence, e.g., in those with cystic fibrosis. Mepacrine is not the drug of choice because side effects are common, including toxic psychosis, and may cause permanent damage. See mefloquine for more information. In addition to medical applications, mepacrine is an effective in vitro research tool for the epifluorescent visualization of cells, especially platelets. Mepacrine is a green fluorescent dye taken up by most cells. Platelets store mepacrine in dense granules.

Mechanism Its mechanism of action against protozoa is uncertain, but it is thought to act against the protozoan's cell membrane. It is known to act as a histamine N-methyltransferase inhibitor. It also inhibits NF-κB and activates p53.

History

Antiprotozoal

Mepacrine was initially approved in the 1930s as an antimalarial drug. It was used extensively during the second World War by Allied forces fighting in North Africa and the Far East to prevent malaria. This antiprotozoal is also approved for the treatment of giardiasis (an intestinal parasite), and has been researched as an inhibitor of phospholipase A2. Scientists at Bayer in Germany first synthesised mepacrine in 1931. The product was one of the first synthetic substitutes for quinine although later superseded by chloroquine.

Anthelmintics In addition it has been used for treating tapeworm infections.

Creutzfeldt–Jakob disease Mepacrine has been shown to bind to the prion protein and prevent the formation of prion aggregates in vitro, and full clinical trials of its use as a treatment for Creutzfeldt–Jakob disease are under way in the United Kingdom and the United States. Small trials in Japan have reported improvement in the condition of patients with the disease, although other reports have shown no significant effect, and treatment of scrapie in mice and sheep has also shown no effect. Possible reasons for the lack of an in vivo effect include inefficient penetration of the blood–brain barrier, as well as the existence of drug-resistant prion proteins that increase in number when selected for by treatment with mepacrine.

Non-surgical sterilization for women The use of mepacrine for non-surgical sterilization for women has also been studied. The first report of this method claimed a first year failure rate of 3.1%. However, despite a multitude of clinical studies on the use of mepacrine and female sterilization, no randomized, controlled trials have been reported to date and there is some controversy over its use. Pellets of mepacrine are inserted through the cervix into a woman's uterine cavity using a preloaded inserter device, similar in manner to IUCD insertion. The procedure is undertaken twice, first in the proliferative phase, 6 to 12 days following the first day of the menstrual cycle and again one month later. The sclerosing effects of the drugs at the utero-tubal junctions (where the Fallopian tubes enter the uterus) results in scar tissue forming over a six-week interval to close off the tubes permanently. In the United States, this method has undergone Phase I clinical testing. The FDA has waived the necessity for Phase II clinical trials because of the extensive data pertaining to other uses of mepacrine. The next step in the FDA approval process in the United States is a Phase III large multi-center clinical trial. The method is currently used off-label. Many peer reviewed studies suggest that mepacrine sterilization (QS) is potentially safer than surgical sterilization. Nevertheless, in 1998 the Supreme Court of India banned the import or use of the drug, allegedly based on reports that it could cause cancer or ectopic pregnancies.

Skin dye During World War II, Caucasian American operatives involved in Sino-American Cooperative Organization activities the Second Sino-Japanese War yellowed their skin using mepacrine tablets in order better blend in with the native Chinese population.

See also Chloroquine Amodiaquine Pamaquine Mefloquine

References

External links National Institute on Aging (NIA) trial

Illustrations

Worked examples

Example 1 — a first encounter with Mepacrine

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

In research: Mepacrine 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 Mepacrine 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: Mepacrine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acridines, Antimalarial agents, Antiprotozoal agents, so understanding it makes those chapters shorter.
In everyday life: Look for Mepacrine 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.

How to study Mepacrine in 20 minutes

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

Frequently asked questions

What is Mepacrine in simple terms?

Mepacrine, also called quinacrine or by the trade names Atabrine or Atebrin, is a medication with several uses. It is related to chloroquine and mefloquine.

Why does Mepacrine 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 Mepacrine?

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 Mepacrine.