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What Is Pentazocine/Naloxone Used For?

Pentazocine/naloxone is a medication prescribed to relieve moderate-to-severe pain in adults and children as young as 12 years old. It contains two medications -- one that helps with pain relief and one that helps prevent abuse of the drug. A healthcare provider may also prescribe this drug to treat mild pain; however this is an off-label (unapproved) use for pentazocine/naloxone.

An Overview of Uses for Pentazocine/Naloxone

Pentazocine/naloxone (Talwin® Nx) is an oral (taken by mouth) prescription medication approved for the treatment of moderate-to-severe pain. It contains a combination of two active ingredients: pentazocine (Talwin®) and naloxone (Narcan®).
Pentazocine is the pain-relieving component of the drug. It is classified as an opioid (narcotic) pain medication. When given as an injection, it is about one-sixth to one-third as potent as morphine. According to the manufacturer, when taken by mouth, 50 mg of pentazocine provides similar pain-relieving effects as 60 mg of codeine. Pentazocine/naloxone contains an oral form of pentazocine.
Like other narcotic medications, pentazocine has the potential for abuse, particularly abuse via injection. Therefore, pentazocine/naloxone contains naloxone, which is added to prevent the drug from being abused. Naloxone has no effect when taken as directed by mouth. However, if pentazocine/naloxone is crushed and injected, the naloxone component cancels out the action of pentazocine, potentially causing withdrawal symptoms.

How Does It Work?

As previously mentioned, this medicine contains pentazocine and naloxone. Pentazocine is the pain-relieving portion of the drug. It works by binding to opioid receptors and mimicking the action of naturally occurring chemicals that block pain. Once taken, pentazocine usually starts to relieve pain in 15 to 30 minutes and can continue to control pain for 3 hours or longer.
The main effects of pentazocine occur when it binds to receptors in the central nervous system (the brain and spinal cord). However, the drug can produce effects anywhere opioid receptors are found in the body.
There are several types of opioid receptors located throughout the body. Pentazocine/naloxone is classified as an opioid agonist-antagonist, which means it binds to and activates certain opioid receptors (kappa receptors), but also blocks certain other opioid receptors (called mu receptors).
As an antagonist at mu opioid receptors, pentazocine/naloxone partially blocks the action of opioid medications that bind to mu receptors, such as morphine. In addition, pentazocine/naloxone is only a partial agonist at kappa receptors, which means it only partially activates them.
Compared to full agonists, such as morphine, partial agonists-antagonists like pentazocine/naloxone usually have a limited effective dosing range. This means there is a maximum dose above which the drug will not have any further effects. This may help make pentazocine/naloxone a less-desirable drug for abuse, and make it less dangerous than full agonist drugs, particularly in the case of an overdose.
The naloxone portion of the medicine helps prevent it from being misused. When taken by mouth as directed, naloxone has no effects in the body. However, if the drug is crushed and injected, naloxone blocks the actions of pentazocine (as well as other narcotic medications), preventing it from working and potentially causing severe withdrawal symptoms. 
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Pentazocine/Naloxone Information

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