A painkiller used to treat moderate to severe pain.

Brand name Talwin.

Works by activating κ-opioid receptors (KOR) and antagonizing μ-opioid receptors (MOR).

An opioid delivering its effects on pain by interacting with the opioid receptors

Side effects include: constipation, nausea, itching, drowsiness and a reduced effort to breathe, but unlike most other opioids it fairly frequently causes hallucinations, nightmares and delusions.

It is subject to a ceiling effect, which is when at a certain dose no more pain relief, or side effects, is obtained by increasing the dose any further.

Pregnancy category US: C (Risk not ruled out) or D (if used near to term)

Routes of administration Oral, IV, IM.

US: Schedule IV

Bioavailability about 20% orally.

Metabolism is hepatic

Onset of action 15 min.

Elimination half-life 2 to 3 hours.

Excretion Renal

Usually, combined with naloxone so as to prevent people from crushing the tablets, dissolving them in a solvent and injecting them for a high.

Rapidly and substantially reduces symptoms of mania in individuals with bipolar disorder that were in the manic phase of the condition.

Adverse side effects are similar to those of morphine.

Due to its action at the kappa opioid receptor it is more likely to invoke psychotomimetic effects.

At high dose it may cause hypertension or tachycardia.

It may also increase cardiac work after myocardial infarction when given intravenously.

Respiratory depression is a common side effect.

Rarely associated with agranulocytosis, erythema multiforme and toxic epidermal necrolysis.

Injection site necrosis and sepsis has occurred with multiple injections.

Classified in Schedule IV.

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