Naltrexone
What is naltrexone?
Naltrexone is a drug that blocks the effects of opiates. When naltrexone is taken, it attaches to the opiate receptors in the brain. This stops opiate molecules being able to bind to the receptors and so the effects or ‘high’ associated with the opiate are eliminated.
Unlike other treatments for opiate dependence such as methadone and buprenorphine, naltrexone dose not produce a ‘high’ and does not cause dependence. It is considered an abstinence therapy, where methadone and buprenorphine are considered to be maintenance therapies.
Naltrexone is currently registered as an oral tablet (Revia® 50mg) for the treatment of opiate and alcohol dependence. It is also used off-label for amphetamine-type stimulants. Naltrexone is also registered in the USA as a 30-day injection (Vivitrol®) for alcohol dependence. Fresh Start also uses a sustained release implantable naltrexone formulation where appropriate known as the O’Neil Long Acting naltrexone Implant.
The naltrexone implant
The O’Neil Long Acting Naltrexone Implant was developed in 1999, because of problems associated with patients not taking oral naltrexone regularly. Since then, the implant has been used in about 3 000 patients including over 270 amphetamine patients and over 250 alcohol patients.
The implant is made of microspheres of naltrexone mixed with a special body-compatible polymer that gradually dissolves, compressed into pellets. Each implant consists of 10 pellets and patients are usually implanted with 2 to 3 implants.
The implants are put under the skin through a small cut below the belt line. Two typical arrangements are shown below. The cut is then closed with a few stitches or medical glue. The procedure is done under local anaesthetic.
The implants are inserted into the subcutaneous tissue of the abdomen, below the belt line.
As the implant breaks down under the skin, naltrexone is released into the body. Naltrexone is released for approximately 3 to 6 months at levels high enough to have the desired effect and continues to release at lower levels for 6 to 12 months. The polymer continues to break down completely over 18 to 30 months.
Patients at Fresh Start Clinic have been treated with the implant under the Special Access Scheme (SAS) or clinical trials. The SAS allows the use of unregistered drugs for the treatment of patients that are at a high risk of premature death. The process of registering the implant for use in Australia is currently underway.
“Everyone we knew took drugs,” Mitchell, 50, says. “Drugs made me feel 10 foot tall and bullet proof but life was only about the next hit; nothing else mattered.” Mitchell’s recovery from a 36-year heroin addiction started last year when he received his first naltrexone implant. “Naltrexone saved my life,” Mitchell says. The road to recovery has not been easy. Although he went back to heroin, Mitchell received a second implant in August and is getting help from his church family to prevent future relapse.
Follow-up
As part of Fresh Start’s commitment to the health and safety of our patients, we are committed to conducting regular follow up interviews on all of our implant patients. The follow up interviews are done over the phone, or in person at 1 week, 4 weeks, 12 weeks and 24 weeks. The interview takes approximately 15 to 25 minutes to complete. All information collected is confidential. The follow up interviews cover areas such as general health and well being, drug use, adverse events and hospital admissions.
Adverse reactions to naltrexone
Naltrexone is generally considered a well tolerated drug with minimal side effects. However, some side effects associated with oral naltrexone include: nausea, headache, dizziness, nervousness, insomnia, vomiting, fatigue, joint and muscle pain, loss of appetite, diarrhoea, constipation, decreased energy. Many of these effects are less severe with implant naltrexone.
In a small number of patients, the implants may cause irritation or inflammation at the site of administration as a result of an allergic response or other inflammatory process. Some tenderness may also be experienced. Please contact the clinic if you experience excessive itchiness or pain, especially between days 14 and 21 after getting an implant (which is when most allergic responses are noticed). Allergic responses can generally be treated successfully with steroids. Allergic responses are estimated to occur in 1% of implant procedures and can usually be managed without removing the implant.
There is a risk of infection with any surgical procedure of this type. Patients are prescribed antibiotics at treatment to prevent infections. If an implant does become infected, the infection can be treated with antibiotics. If the area does not respond to antibiotics the implants may need to be surgically removed. This is extremely rare.
Pain Relief
In the unlikely event that you require narcotic painkillers for severe pain during the active phase of your naltrexone implant, these types of painkillers may have a reduced effect whilst naltrexone is still being released from the implant. If Panadol, Tramadol or non-steroidal tablets (eg Ibuprofen) do not work, pain relief should be managed by an anaesthetist. Anaesthetists can usually manage pain with ketamine, intravenous patient controlled analgesia, sedation or local regional blocks.