Nefopam

Nefopam (Acupan) is a centrally-acting but non-opioid analgesic drug of the benzoxazocine chemical class which was developed in the early 1970s. It is widely used, mainly in European countries, for the relief of moderate to severe pain as an alternative to opioid analgesic drugs. Animal studies have shown that nefopam has a potentiating (analgesic-sparing) effect on morphine and other opioids by broadening the antinociceptive action of the opioid and possibly other mechanisms, generally lowering the dose requirements of both when they are used concomitantly.

Use
Nefopam has additional action in the prevention of shivering, which may be a side effect of other drugs used in surgery.

Nefopam at a dose of 30–120 mg is significantly more effective than aspirin as an analgesic, although with a greater incidence of side effects such as sweating, dizziness and nausea, especially at higher doses.

Nefopam is around half the potency and slightly less effective as an analgesic compared to morphine, or oxycodone, but 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 opioids, or as an adjunctive treatment for use alongside opioid(s) or other analgesics.

Nefopam is also used to combat severe hiccups.

Pharmacology
The mechanism of action of nefopam is not well understood, although inhibition of serotonin, dopamine and noradrenaline reuptake is thought to be involved in its analgesic effects,  and there may be other modes of action such as through histamine H3 receptors and glutamate. Recently, like its analogue orphenadrine which also has analgesic effects, nefopam has been found to act as a voltage-gated sodium channel blocker, and this may in part or fully mediate its antinociceptive effects.

Recreational Use/Overdose
Recreational use of nefopam and death from overdose have both been reported, although these events are less common with nefopam than with opioid analgesic drugs.