Naloxone

Absorption

An intranasal dose of naloxone is 42-47% bioavailable. An 8 mg dose of nasal naloxone reaches a Cmax of 12.3-12.8 ng/mL, with a Tmax of 0.25 hours, and an AUC of 16.7-19.0 h*ng/mL. A 0.4 mg intramuscular dose reaches a Cmax of 0.876-0.910 ng/mL, with a Tmax of 0.25 hours, and an AUC of 1.94-1.95 h*ng/mL. A 2 mg intravenous dose reaches a Cmax of 26.2 ng/mL with an AUC of 12.8 h*ng/mL.

Toxicity

If a patient has not taken opioids, naloxone does not have a significant effect on patients.
The oral LD50 in mice and rats is >1 g/kg. The intraperitoneal LD50 is 80 mg/kg in mice and 239 mg/kg in rats. The subcutaneous LD50 is 286 mg/kg in mice and 500 mg/kg in rats.

Description

It is worth mentioning that N-allylic substitution in a number of morphine derivatives, as a rule, leads to antagonistic properties. Naloxone is a few times stronger than nalorphine as an antagonist. It blocks opiate receptors. It eliminates central and peripheral action of opioids, including respiratory depression. Naloxone is used upon overdose of narcotic analgesics.

Description

Naloxone—sold primarily under the trade name Narcan—has been widely publicized as a “rescue” drug for people whose lives are in danger from opioid overdoses. But this complex multiring compound has a long history.
Naloxone, a relative of morphine, has been recognized as an opiate antagonist since the early 1960s, when Mozes J. Lewenstein and Jack Fishman patented its synthesis in the United States, and the Japanese company Sankyo (now Daiichi Sankyo) patented it in Britain, among other countries.
In 1971, the US Food and Drug Administration approved it for treating opiate overdoses by intravenous or intramuscular injection. The moribund patient often begins breathing and regains consciousness immediately. The rapid rise in prescription painkiller and heroin overdoses in the past decade spurred practitioners to seek ways other than injection to administer naloxone. At first, people improvised devices to deliver the drug nasally, but the results were often inadequate because of improper personnel training or inconsistent dosages.
In 2012, Phil Skolnick at the National Institute on Drug Abuse and Roger Crystal, CEO of Opiant Pharmaceuticals (formerly Lightlake Therapeutics) joined forces to?develop an intranasal naloxone applicator?that would be easy to use and would supply a known amount of drug. FDA approved the device in November 2015. In February of this year, Opiant/Lightlake’s partner Adapt Pharma began to distribute Narcan nasal spray in the 38 states where it has been approved for use without a prescription. In the meantime, the Kaléo pharmaceutical company has begun to distribute Evzio, a new naloxone autoinjector.

Originator

Narcan,Du Pont,US,1971

The Uses of Naloxone

Naloxone is a specific opioid antagonist. Narcotic antagonist.

The Uses of Naloxone

antineoplastic

Indications

Naloxone nasal sprays are indicated for the reversal of an opioid overdose or suspected opioid overdose: it is intended for immediate administration as emergency therapy in settings where opioids may be present. Intramuscular, intravenous, and subcutaneous injections are indicated for complete or partial reversal of opioid depression, diagnosis of known or suspected opioid overdose, and as an adjunct therapy in the treatment of septic shock.
Sublingual tablets and films are formulated with buprenorphine for the treatment of opioid dependence. Naloxone is also formulated with pentazocine as an oral tablet for severe pain.
Intramuscular or subcutaneous naloxone autoinjectors are used for the emergency treatment of people 12 years of age and older where the use of high-potency opioids such as fentanyl analogues as a chemical weapon, is suspected.
Naloxone has been used off-label for the treatment of neuraxial opioid-induced pruritus.

Background

Naloxone is an opioid antagonist medication used to block or reverse the effects of opioid drugs, particularly within the setting of drug overdoses which are rapidly becoming a leading cause of death worldwide. More specifically, naloxone has a high affinity for μ-opioid receptors, where it acts as an inverse agonist, causing the rapid removal of any other drugs bound to these receptors. When taken in large quantities, opioid medications such as morphine, hydromorphone, methadone, heroin, or fentanyl are capable of causing life-threatening symptoms such as respiratory depression, reduced heart rate, slurred speech, drowsiness, and constricted pupils. If untreated, this can progress to vomiting, absent pulse and breathing, loss of consciousness, and even death. Naloxone is indicated for the rapid reversal of these symptoms of central nervous system depression in opioid overdose. It's important to note that naloxone only works on opioid receptors within the body, and is therefore not capable of reversing the effects of non-opioid medications such as stimulants like methamphetamine or cocaine, or benzodiazepines like lorazepam or diazepam.
Also known as the brand name product Narcan, naloxone is currently available by intramuscular (IM) or subcutaneous (SubQ) injection, nasal spray, or intravenous (IV) infusion. Naloxone IM injections are commonly available in the form of "kits", which is ideal for making overdose treatment accessible and readily available for administration by minimally trained individuals within the community. Kits commonly include the supplies necessary to treat an overdose in a non-medical setting such as alcohol swabs, syringes, a rescue breathing mask, and instructions for use. Frequently also carried by medical and emergency personnel and at events known to be associated with heavy drug use like music festivals, naloxone kits are considered a key component of harm reduction strategies. There are over-the-counter nasal sprays available.
When injected intramuscularly (IM), naloxone acts within three to five minutes. Administration of naloxone is associated with very few side effects. Notably, if injected into a person not currently using opioid medications, there would be no noticeable effects at all. However, for individuals using opioid medications or experiencing an overdose, IM injection of naloxone rapidly reverses opioid effects and can cause the injected individual to immediately experience withdrawal symptoms. Common symptoms of opioid withdrawal include nausea, vomiting, sweating, runny nose, aches, and diarrhea. Although certainly physically uncomfortable, opioid withdrawal symptoms are not life-threatening; administration of naloxone is, therefore, appropriate for any person appearing to have any symptoms of an opioid overdose. Due to its short duration of action, persons injected with naloxone should be monitored for responsiveness and potentially injected a second time or taken to the hospital.
Naloxone is also available within the combination product Suboxone with the opioid medication buprenorphine. Suboxone is used for the maintenance treatment of opioid dependence and addiction. When taken orally, naloxone has no pharmacological effect and does not reduce the effectiveness of the opioid effect of buprenorphine. The primary purpose of including naloxone within Suboxone is to act as a deterrent to injection, as injected naloxone would rapidly reverse the effects of buprenorphine.
Naloxone was granted FDA approval on 13 April 1971.

Definition

ChEBI: A synthetic morphinane alkaloid that is morphinone in which the enone double bond has been reduced to a single bond, the hydrogen at position 14 has been replaced by a hydroxy group, and the methyl group attached to the nitrogen has been replaced by an all l group. A specific opioid antagonist, it is used (commonly as its hydrochloride salt) to reverse the effects of opioids, both following their use of opioids during surgery and in cases of known or suspected opioid overdose.

Manufacturing Process

10 grams of 14-hydroxydihydromorphinone (oxymorphone) was converted into its diacetate by warming it on the steam bath with 80 cc of acetic anhydride for about 2 hours. The acetic anhydride was removed on the water bath under a vacuum of about 30 mm absolute pressure. The melting point of the residue was 220°C. The residue was taken up in 100 cc of chloroform. An equal amount by weight of cyanogen bromide was added and the mixture was refluxed at about 60°C for about 5 hours. After refluxing, the mixture was washed with 100 cc of a 5% aqueous hydrochloric acid solution, dried over sodium sulfate and the chloroform removed by evaporation under a vacuum of about 30 mm. The residue had a melting point of 240°C.
The residue was then heated at about 90°C for 16 hours on a steam bath with 300 cc of 20% aqueous hydrochloric acid solution, and treated with a small amount, e.g., 1 gram of charcoal. The hydrochloric acid was then removed under a vacuum of 15 mm, the residue dissolved in 30 cc of water and precipitated by the addition of 2.4 cc of concentrated aqueous ammonia. The precipitate was filtered off and dried. It consists of 14- hydroxydihydronormorphinone. It is soluble in ethanol.
The 14-hydroxydihydronormorphinone was suspended in 200 cc of pure ethyl alcohol, half its weight of sodium bicarbonate and half its weight of allyl bromide added and the resulting mixture was refluxed at about 75°C for 48 hours. The solution was cooled, e.g., to 10°C and filtered and the alcohol removed under a vacuum of 30 mm. The residue was dissolved in chloroform and filtered. The chloroform was removed under a vacuum of 30 mm and the residue was crystallized from ethylacetate. The crystallized product, N-allyl- 1,4-hydroxydihydronormorphinone, has a melting point of 184°C, is soluble in chloroform and insoluble in petroleum ether. The yield amounts to 20% based on the weight of the reacted 14-hydroxydihydromorphinone.

brand name

Narcan (Bristol-Myers Squibb); Narcan (Endo).

Therapeutic Function

Narcotic antagonist

Biological Functions

Because of its fast onset (minutes), naloxone (Narcan) administered IV is used most frequently for the reversal of opioid overdose. However, it fails to block some side effects of the opioids that are mediated by the δ- receptor, such as hallucinations. The rapid offset of naloxone makes it necessary to administer the drug repeatedly until the opioid agonist has cleared the system to prevent relapse into overdose. The half-life of naloxone in plasma is 1 hour. It is rapidly metabolized via glucuronidation in the liver and cleared by the kidney. Naloxone given orally has a large first-pass effect, which reduces its potency significantly. Often an overshoot will follow the administration of naloxone for overdose. The heart rate and blood pressure of the patient may rise significantly. The overshoot is thought to be due to precipitation of acute withdrawal signs by naloxone. Given alone to nonaddicts, naloxone produces no pharmacological effects.
Naloxone is approved for use in neonates to reverse respiratory depression induced by maternal opioid use. In addition, naloxone has been used to improve circulation in patients in shock, an effect related to blockade of endogenous opioids. Other experimental and less well documented uses for naloxone include reversal of coma in alcohol overdose, appetite suppression, and alleviation of dementia from schizophrenia. Side effects of naloxone are minor.

General Description

Naloxone (Narcan) is a pure antagonist at allopioid receptor subtypes. Structurally, it resembles oxymorphoneexcept that the methyl group on the nitrogen isreplaced by an allyl group. This minor structural change retains high binding affinity to the receptor, but no intrinsicactivity. It is used to reverse the respiratory depressant effectsof opioid overdoses.
Naloxone is administered intravenously with an onset ofaction within 2 minutes. Because it is competing with theopioid for the receptor sites, the dose and frequency of administrationwill depend on the amount and type of narcoticbeing antagonized. Overdoses of long-acting opioids(methadone) may require multiple IV doses of naloxone orcontinuous infusions. Neonates born to opioid-exposedmothers may be given IV naloxone at birth to reverse the effectsof opiates.
Very few metabolism studies on naloxone have beenconducted, although the major metabolite found in the urineis naloxone-3-glucuronide.

Pharmacokinetics

Naloxone is an opioid receptor antagonist indicated in the reversal of opioid overdoses. Naloxone has a shorter duration of action than opioids and multiple doses may be required. The therapeutic window of naloxone is wide, as it has no effect if a patient has not taken opioids. Patients treated with naloxone may experience opioid withdrawal and a person administering naloxone should be aware that reversal of opioid overdoses may not resolve all the symptoms a patient is experiencing if other drugs are involved.

Clinical Use

Naloxone has no analgesic activity. The compound is the standard antidote to treat opioid adverse reactions, opioid overdoses, or to stop an intended use of an opioid compound. Typical indications are inhibition of opioid-induced respiratory depression, termination of opioid anesthesia or protection of neonates following opioid treatment during labor. Naloxone has a short duration of action and repetitive administration may be necessary to antagonize longer acting agonists. To avoid parenteral misuse of nonscheduled oral opioid formulations (tilidine, pentazcocine), a small amount of naloxone is added which is orally inactivated, but is fully active after parenteral administration.
Naloxone is orally inactive and is only used parenterally in single or repetitive doses of 0.4– 2 mg up to a total dose of 10 mg, as an intravenous bolus injection or by infusion. The compound is more potent against pure opioid agonists than against mixed agonist – antagonists. Caution should be used in opioid-dependent persons or in persons under high-dose opioid treatment, as naloxone may precipitate an acute withdrawal reaction. Naloxone is relatively free of side effects. Nausea, vomiting, and convulsions have occasionally been reported.

Synthesis

Naloxone, (-)-17-(allyl)-4,5-epoxy-3,14-dihydroxymorphinan-6-one (3.1.92), is synthesized by the alkylation of 14-hydroxydihydronormorphinane (3.1.82) by allylbromide [55¨C58].

Metabolism

Naloxone primarily undergoes glucuronidation to form naloxone-3-glucuronide. Naloxone is also N-dealkylated to noroxymorphone or undergoes 6-keto reduction to naloxol.