NALTREXONE IMPLANTS

This clinical overview explores the history, science and development of sustained-release naltrexone implants.

Established in 2001, Naltrexone Implant Clinic RYW provides medical consultations, detoxification assessments and long-acting naltrexone implant treatment for patients travelling from London and elsewhere in the UK, Ireland and across Europe.

Naltrexone implants are sustained-release formulations developed to deliver naltrexone gradually over an extended period. Naltrexone is an opioid receptor antagonist used in the treatment of opioid dependence and, in a different clinical context, alcohol dependence. Implant development has involved different formulations and approaches to controlling medication release, with variations in composition and intended duration.

This article traces the development of naltrexone implants, from early pellet-based formulations to later sustained-release designs. It also examines how the implants work, their potential benefits and limitations, liver safety considerations, and the clinical evidence and regulatory issues surrounding their use.

For information on treatment suitability, available implant options, procedures and current fees, please visit our Naltrexone implant patient guide and the Pricing pages.

Contact us via WhatsApp +447424474635

Our patients’ positive experiences with naltrexone implants for alcohol dependence

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What is Naltrexone?

Naltrexone is an opioid receptor antagonist. It blocks opioid receptors, reducing or preventing the effects of opioid drugs such as heroin, morphine and other opioids. It is also used in the treatment of alcohol dependence, where it can help reduce the rewarding effects of alcohol and the risk of heavy drinking.

Learn more about Naltrexone pills 

Naltrexone is available in different formulations, including oral tablets and long-acting preparations. Oral tablets are usually taken daily, while sustained-release implants are designed to deliver medication gradually over an extended period. This can reduce the need to remember daily doses, although the release profile and duration depend on the formulation used.

Unlike oral naltrexone, which is taken regularly by mouth, a slow-release implant delivers naltrexone over time. The medication still enters the bloodstream and is metabolised by the body, including the liver. A sustained-release formulation should not automatically be assumed to have no liver-related risks.

Naltrexone does not cause opioid-type physical dependence. However, stopping treatment removes its opioid-blocking effect, and the risk of relapse may remain. Following detoxification, reduced opioid tolerance can also increase the risk of a potentially fatal overdose if opioid use resumes.

Naltrexone treatment must be carefully planned. Patients must be free from opioids before treatment begins because starting naltrexone too soon can precipitate severe withdrawal. An appropriate medical assessment is therefore essential before an implant is considered.

Read more about Naltrexone implants

History and development of Naltrexone implants

Naltrexone was synthesized in the 1960s. Scientists had first used Naltrexone clinically in the early 1970s. It soon became evident that its therapeutic potential was undermined by poor compliance. Therefore, the first studies of depot Naltrexone date from the mid 70s. Human studies took place in the early 1980s, and most of the basic science was known by then.

85% Naltrexone implants success rate in alcohol addiction treatment reported in the USA

Is Naltrexone toxic?

Oral naltrexone at the standard dose of 50 mg daily undergoes substantial first-pass metabolism in the liver, whereas sustained-release implants are designed to deliver the medication gradually over time. Because implants bypass the heavy hepatic first-pass spikes associated with daily oral dosing, they usually present a lower risk of liver toxicity, though this can depend on the specific formulation and requires supporting clinical evidence.

First generation of Naltrexone blockers

The first Naltrexone implants for clinical trials took place around 1997th. Dr Lance L Gooberman (Pellet Technologies LLC, NJ), George Malmberg (Wedgewood Pharmacy, NJ) and Alan R Tripp were the first experts to test them. See the patent

These ‘first generation’ implants consisted of a cigarette-butt size pellet. It was made of

• - compressed naltrexone powder
• - small percentage of magnesium stearate
• - slow-release triamcinolone

Magnesium stearate is a normal component of implants. However, it sometimes causes tissue irritation. Therefore, 10 mg of slow-release triamcinolone was added to reduce allergic reactions.

These drug implants dissolve and disappear completely in about  5-7 weeks on average.

All these changed have led to Naltrexone implants success rate significant improvements.

Pharmacy of a Berlin hospital has made similar drug implant for internal use . Thanks to removing stearate component better tissue tolerability was achieved. These implant became available at theend of 2006.

George Sherman (USA) at Towne Pharmacy has  manufactured the later implant. It is a 1g  pellet with 10mg of slow release triamcinolone. It is manufactured in a more advanced manner producing effective opioid blockage for 12 to 14 weeks.

The same product is now licensed in Russia as Prodetoxone. It is currently being used in three extensive trials. The trials are conducted at St.Petersburg Scientific-Research Centre of Addictions and Psychopharmacology. Also at Pavlov Medical University, St.Petersburg,Russia in conjunction with the University of Pennsylvania, Department of Psychiatry, Philadelphia, USA. Naltrexone implants success rate in Russia is not known because of lack research.

Naltrexone prices in British pounds - £ (UK).

Second generation of Naltrexone implants

Second generation’ of Naltrexone implants apply another established implant technique. Dr George O’Neill of GO-Medical Industries in Perth (an article about Dr George O'Neil in ABC), WA had made the first implant of this type.  The pellet takes longer to dissolve and naltrexone is released for 5-12 months or more. The effectiveness  may be only partial after about 9-13 months though.

These implants are generally well-tolerated and there is no need to include a steroid. Both types of implants are usually inserted with antibiotic prophylaxis. They also can block very large amounts of heroin thanks to containing large quantity of Naltrexone.

Basic composition of the O’Neill implant is as follows:

• - 50% naltrexone
• - 49% of biodegradable polymer
• - 1% magnesium stearate

The polymer material is similar material to that used in biodegradable sutures and has the FDA’s license.

Types of Naltrexone implants

There are several "new" second generation implants:

The most recent is the LI LA naltrexone implant from China, and is also based on the use of biodegradeable polymer. However, the LI LA naltrexone implant appears to give good blood levels and hence effective opiate blockage over one year.

Afterwords three American companies have developed blockers:

1. Addex naltrexone implants - Bartor Pharmacal Inc.

2. Trident naltrexone implants - Trident Inc.

3. Hydron naltrexone implants - Valera Pharma Inc. the implants are at various stages of development.

The polymer technology used in sustained-release naltrexone formulations has also been applied to depot injections. Alkermes Inc. in the USA developed Vivitrol, an extended-release naltrexone formulation administered as an intramuscular injection. Vivitrol uses biodegradable polymer microspheres to release naltrexone gradually and is approved by the US Food and Drug Administration (FDA) for the treatment of alcohol dependence and for the prevention of opioid relapse following opioid detoxification. Unlike naltrexone implants, Vivitrol is administered by injection and does not require surgical insertion beneath the skin.