Nefopam

Key takeaways

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

Reference excerpt

Nefopam, sold under the brand name Acupan among others, is a centrally acting, non-opioid analgesic medication, with stimulant and sympathomimetic properties that is primarily used to treat moderate to severe pain.

History Nefopam is based on a benzoxazocine compound. It was developed in the 1960s and marketed under the name fenazocine. It was initially used in shivering, as a muscle relaxant and as an antidepressant, but then increasingly as an analgesic.

Medical uses

Analgesic Nefopam was significantly more effective than aspirin as an analgesic in one clinical trial, although with a greater incidence of side effects such as sweating, dizziness and nausea, especially at higher doses. The estimated relative potency of nefopam to morphine indicates that 20 mg of nefopam HCl is the approximate analgesic equal of 12 mg of morphine with comparable analgesic efficacy to morphine, or oxycodone. Nefopam tends to produce fewer side effects, does not produce respiratory depression, and has much less abuse potential, and so is useful either as an alternative to opioid analgesics, or as an adjunctive treatment for use alongside opioids or other types of analgesics.

Postoperative pain A 2025 review, covering 17 studies, found that nefopam was an effective adjunctive postoperative analgesic with benefits in pain management, and correlated with a mean decrease in opioid consumption across the studies of 38%. Adverse effects were not discussed in detail in the included studies.

Chronic pain For chronic pain nefopam may sometimes be used when common alternatives are contraindicated or ineffective, or as an add-on therapy.

Other medical uses Nefopam is used to treat severe hiccups. Nefopam is thought to have some efficacy for treating (off-label) Parkinson's disease, in a similar fashion to those of Bupropion and Methylphenidate.

Nefopam is effective for prevention of shivering during surgery or recovery from surgery.

Dosage Dosage is normally 90-180mg per day. Maximum dose is regarded as 270mg/day. One 1979 study found that a ceiling effect on post-operative pain relief occurred at 60mg/day.

Contraindications Nefopam is contraindicated in people with convulsive disorders, those that have received treatment with irreversible monoamine oxidase inhibitors such as phenelzine, tranylcypromine or isocarboxazid within the past 30 days and those with myocardial infarction pain, mostly due to a lack of safety data in these conditions.

Side effects Common side effects include nausea, nervousness, dry mouth, light-headedness and urinary retention. Less common side effects include vomiting, blurred vision, drowsiness, sweating, insomnia, headache, confusion, hallucinations, tachycardia, aggravation of angina and rarely a temporary and benign pink discolouration of the skin or erythema multiforme.

CNS side effects Some side effects, such as feeling confused or hallucinating, are more likely in patients over 65 years old. Nefopam has been shown to have anticholinergic properties and has a score of 2 on the anticholinergic burden (ACB) scale.Anticholinergic drugs have caused concerns about cognitive decline in older people.

Overdose Overdose and death have been reported with nefopam. Overdose usually manifests with convulsions, hallucinations, tachycardia, and hyperdynamic circulation. Treatment is usually supportive, managing cardiovascular complications with beta blockers and limiting absorption with activated charcoal.

Interactions Nefopam has additive anticholinergic and sympathomimetic effects with other agents with these properties. Its use should be avoided in people receiving some types of antidepressants (tricyclic antidepressants or monoamine oxidase inhibitors) as there is the potential for serotonin syndrome or hypertensive crises to result.

Mechanisms of action The mechanism of action of nefopam and its analgesic effects are not well understood.

Analgesic mechanisms of action Nefopam may have three analgesic mechanisms in the brain and spinal cord;

antinociceptive pain modulation effects by triple neurotransmitter reuptake inhibition of serotonin, norepinephrine, and dopamine (that is, acting as an SNDRITooltip serotonin–norepinephrine–dopamine reuptake inhibitor). antihyperalgesic activity through modulation of glutamatergic transmission via modulating sodium and calcium channels. inhibition of long-term potentiation mediated by NMDA from the inhibition of calcium influx.

Pharmacology A 2025 review noted a significant literature gap on the pharmacokinetic and pharmacodynamic properties of nefopam.

Pharmacokinetics The absolute bioavailability of nefopam is low. It is reported to achieve therapeutic plasma concentrations between 49 and 183 nM. The drug is approximately 73% protein-bound across a plasma range of 7 to 226 ng/mL (28–892 nM). The metabolism of nefopam is hepatic, by N-demethylation and via other routes. Its terminal half-life is 3 to 8 hours, while that of its active metabolite, desmethylnefopam, is 10 to 15 hours. It is eliminated mostly in urine, and to a lesser extent in feces.

Chemistry Nefopam is a cyclized analogue of orphenadrine, diphenhydramine, and tofenacin, with each of these compounds different from one another only by the presence of one or two carbons. The ring system of nefopam is a benzoxazocine system.

Manufacture A 2025 review highlighted the difficulties and environmental costs of current Nefopam manufacturing processes, but the potential for improvement.

Use by country Nefopam is used in the UK, under prescription only, although some UK regions do not advise initiation of use. It is used in France, although some concerns have been raised, due to it being misused, as it was used orally instead of intravenously.. An oral form is now commercialized in France, as to lessen the misuse of the intravenous form. As of 2014 Nefopam was not FDA-approved in the US.

Society and culture

Recreational use Recreational use of nefopam has rarely been reported, and is far less common than with opioid analgesics.

Illustrations

Worked examples

Example 1 — a first encounter with Nefopam

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

In research: Nefopam 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 Nefopam 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: Nefopam is common in secondary-school and first-year university syllabi. It links to neighbouring topics Analgesics, Drugs with unknown mechanisms of action, Muscarinic antagonists, so understanding it makes those chapters shorter.
In everyday life: Look for Nefopam 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 Nefopam in 20 minutes

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

Frequently asked questions

What is Nefopam in simple terms?

Nefopam, sold under the brand name Acupan among others, is a centrally acting, non-opioid analgesic medication, with stimulant and sympathomimetic properties that is primarily used to treat moderate to severe pain. History Nefopam is based on a benzoxazocine compound.

Why does Nefopam 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 Nefopam?

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 Nefopam.