Morphine and related drugs: Fentanyl citrate, Methadone hydrochloride, Propoxyphene hydrochloride, Pentazocine, Levorphanol tartrate : Pharmaguideline -->

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Morphine and related drugs: Fentanyl citrate, Methadone hydrochloride, Propoxyphene hydrochloride, Pentazocine, Levorphanol tartrate

Morphine analogues are a class of drugs similar to morphine in their effects on the body.

SAR of Morphine analogues

Morphine analogues are a class of drugs similar to morphine in their effects on the body. These drugs treat pain and other conditions such as anxiety, depression, and addiction.
  • Some of these drugs, such as codeine and hydrocodone, are available over the counter; others, such as oxycodone and fentanyl, are available only by prescription.
  • Full agonists produce effects similar to those of morphine, while partial agonists produce weaker effects.
  • Morphine and its analogues are typically well-tolerated, but they can cause side effects.
  • These include drowsiness, constipation, nausea, and vomiting. Some of these drugs can also cause respiratory depression, which can be fatal.
Morphine and its analogues are schedule II drugs in the United States, which means they have a high potential for abuse and addiction.

SAR of Fentanyl citrate

Fentanyl citrate, also known as Sublimaze, is a potent, short-acting synthetic opioid analgesic medication. It is similar to morphine in its effects but more potent and has shorter acting.
  • It is typically used intravenously for surgery, severe pain, or epidurally for childbirth. Fentanyl was first synthesized by Paul Janssen in 1960 and approved for medical use in the United States in 1968.
  • Fentanyl citrate is a white powder that is insoluble in water. It is available in various formulations, including sublingual tablets, buccal tablets, transdermal patches, lozenges, and intranasal sprays.
  • The usual side effects of fentanyl citrate are nausea, vomiting, constipation, drowsiness, and dizziness.
  • Serious side effects include slowed or shallow breathing, low blood pressure, and fainting.
Fentanyl citrate is a powerful opioid medication that is only available by prescription. It is important to use it only as directed by a healthcare provider.

SAR of Methadone hydrochloride

Methadone hydrochloride is a medication used to treat pain and addiction. It works by binding to the same brain receptors as opioids but with a weaker effect.

This reduces the cravings for opioids and the risk of withdrawal symptoms. It is available only through a certified methadone treatment program.

SAR of Propoxyphene hydrochloride

The maximum recommended daily dose of propoxyphene is 100 mg. Propoxyphene hydrochloride has a potency similar to that of pentazocine.

Propoxyphene's action duration is usually four to six hours but may be prolonged in some individuals for up to 12 hours or longer.

Propoxyphene is well absorbed from the gastrointestinal tract, and peak plasma concentrations occur within two to three hours after an oral dose.

Propoxyphene is extensively bound to plasma proteins, and the free fraction in plasma is only about 5%. Metabolism of propoxyphene occurs primarily in the liver by N-demethylation to norpropoxyphene.

Norpropoxyphene is pharmacologically active but has one-sixth the potency of propoxyphene.

The elimination half-life of propoxyphene is usually three to four hours but may be prolonged in some individuals for up to eight hours or longer.

Propoxyphene and norpropoxyphene are excreted in the urine, primarily as conjugates.

Propoxyphene's most common adverse effects are drowsiness, dizziness, and lightheadedness. These effects may be dose-related and more pronounced in the elderly and debilitated.

Other less common adverse effects include nausea, vomiting, constipation, abdominal pain, headache, and rashes. Rarely, propoxyphene may cause hypotension, bradycardia, shortness of breath, and seizures.

Propoxyphene may also interact with various other drugs, including MAO inhibitors, tricyclic antidepressants, and warfarin.

SAR of Pentazocine

Pentazocine is a medication commonly which has been used to relieve pain ranging from moderate to severe. It is classified as an opioid agonist-antagonist, which means that it works by binding to opioid receptors in the brain and spinal cord to decrease the perception of pain.

Pentazocine also has a milder effect on the central nervous system than other opioids, making it a safer option for pain relief. The usual side effects of pentazocine include nausea, vomiting, and dizziness.

More serious side effects include slowed heart rate, low blood pressure, and respiratory depression.

Pentazocine should be used with caution in people with liver or kidney disease and those with a history of substance abuse.

SAR of Levorphanol tartrate

The levorphanol tartrate salt of (-)-(R)-2-methyl-3-(morpholino ethyl)morphinan is a white, crystalline solid with a molecular weight of 379.47.

Levorphanol tartrate is the active moiety of levorphanol and is a potent, centrally acting analgesic. Levorphanol tartrate has a binding affinity for mu-, kappa- and delta-opioid receptors.

It produces both supraspinal and spinal analgesia. The analgesic effect of levorphanol is 4 to 5 times that of morphine sulfate on a milligram basis.

The pharmacokinetics of levorphanol tartrate have been studied in healthy volunteers as well as the patients suffering from chronic pain. Following a 2 mg dose of levorphanol tartrate, the peak plasma concentration is reached in 1 to 2 hours.

The most common adverse reactions associated with levorphanol tartrate use are nausea, vomiting, dizziness, lightheadedness, and drowsiness. These effects are usually mild and resolve with continued treatment.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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