Dextropropoxyphene: What It Is And How It Works

Like morphine and methadone, dextropropoxyphene is a drug from the opioid group. It is used as a pain reliever for pain that is mild to moderate in intensity. Unlike other pain relievers, it has no antipyretic or anti-inflammatory effects.

Like the rest of opioids, this drug has an effect on the central nervous system, by binding to opiate receptors ; this union diminishes the sensation of pain.

The opioid system and dextropropoxyphene

The opioid system is a set of proteins and its receptors are responsible for modulating pain. The receptors are widely distributed throughout the central nervous system (brain and spinal cord).

In the human body,  the transmission of pain is through the nociceptive pathways . These pathways carry pain sensation from the site of damage to the central nervous system.

Under these circumstances, the opioid system is activated and inhibits this transmission. With this, the painful sensation decreases, that is, analgesia occurs.

There are three types of molecules of the organism that activate this system:

• Endorphins.
• Encephalins.
• Dinorphins.

These molecules bind to opioid receptors, activating them  and producing different effects. There are different types of receptors, the main ones are: kappa, delta, sigma and mu. Although each one has some characteristics, its activation produces in general features:

• Sedation.
• Analgesia.
• Respiratory depression
• Digestive symptoms, such as constipation or vomiting.

Data of interest

As the scientific literature indicates, opioids are involved in the reward circuit. The reward circuit is a physiological mechanism present not only in humans, but in all mammals. The purpose of this system is to strengthen those behaviors that produce pleasure, such as eating.

Activation of this system releases large amounts of dopamine ; which produces a pleasant sensation that facilitates learning and reinforcement of behavior.

Opioids alleviate pain, so their use is related to this circuit. This is the reason why the use of this type of medication can lead to dependence. Therefore, it must be regulated and always supervised by a doctor.

Dextropropoxyphene binds to opioid receptors, activating them, replacing in some way the action of endogenous opioids. This mechanism of action is called agonism, so dextropropoxyphene is an opioid agonist drug. 

Administration

Dextropropoxyphene is used orally. Once ingested, it is absorbed in the digestive tract quickly, passing into the blood. It is distributed through the circulatory stream, reaching the maximum concentration 2 hours after taking it.

It accumulates mainly in the brain, lungs, and liver. Like many other drugs, it is metabolized in the liver by a demethylation process.

Most of the demethylated dextropropoxyphene, which is called norpropoxyphene. This travels to the kidneys and is eliminated with the urine.

Indications

Dextropropoxyphene is used as a pain reliever. With regard to pain, different lines of treatment known as therapeutic steps are followed :

• The first step is made up of paracetamol and non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen.
• When these are not enough to relieve pain, it goes to the second step, where weak opioids such as dextropropoxyphene or tramadol enter. Opioid drugs can be used alone or in combination with other types of drugs.
• If the pain is severe and cannot be controlled with weak opioids, other stronger types of opioids are used, such as morphine or fentanyl, which constitute the third step. Like weak opioids, they can be associated with other types of pain relievers.

Side effects

Some side effects that this medicine can cause are the following:

• Changes in mood. 
  • Euphoria.
  • Anxiety.
  • Depression.
• Agitation.
• Disorientation.
• Insomnia / Drowsiness.
• Sickness.
• Vomiting
• Constipation.
• Urinary retention.
• Tolerance (in prolonged treatments).

As soon as you suspect that you are suffering from any of the aforementioned adverse reactions, you should consult your doctor. The professional will be the one who must proceed to evaluate the patient’s situation and take measures depending on the case.

Precautions

The use of opioid drugs in medicine is widespread and regulated. However, not all patients are candidates for the use of this type of medication.

Given that these drugs can produce dependence and tolerance, their withdrawal must be directed by the doctor and can never be abrupt, since this could cause a withdrawal syndrome, among other health complications.

Dextropropoxyphene is contraindicated in patients with:

• Respiratory pathologies such as asthma or COPD, due to the respiratory depression effect of this drug.
• Depressive disorder. Especially if they have suicidal tendencies (because they are predisposed to addiction to these substances).
• Severe liver or kidney failure, as it interferes with the metabolism and elimination of the drug and there may be an increased risk of overdose.
• Allergy to dextropropoxyphene or to another drug in this group.

Dextropropoxyphene overdose causes severe respiratory depression that can sometimes be fatal. To counteract this effect, naltrexone is used, which blocks opioid receptors.