One of the most serious concerns is the possibility of severe allergic pneumonia, which given the nature of the products involved may be prolonged. In the featured study, pre-testing patients with oral naltrexone did not alert medical staff to allergic reactions It is not clear what form these took. in the three patients who developed them. Several other studies have not reported such reactions and it remains unclear how common they are. Pre-testing with small doses of the long-lasting product has been advised.
Such considerations will be taken in to account in any decision to licence implants or depot injections for medical use. A depot injection whose opiate-blocking effects last about a month (1 2) has been licensed in the USA, but for the treatment of alcohol dependence. Since this is injected it avoids the surgical procedure required for implants and cannot be removed Or by medical staff, meaning that opiate-based pain relief is irreversibly compromised while the injection remains active. by the patient. Side effects are generally mild and/or short-lived and not sufficient to cause patients to discontinue treatment. However, injection site complications are not uncommon and occasionally severe. These may be considered of greater concern among alcohol patients than drug injectors, for whom naltrexone injections may prevent the perhaps greater risks of injecting site damage due to unhygienic injection of illegal opiates.
The single implant patient who in the featured study repeatedly overdosed shows that this is possible, but fatal overdose seems rare. In Australia over the five years from 2000 to 2004, coroners recorded just one clear case of death from opiate overdose in a patient with an active naltrexone implant, and a further case where the patient overdosed on a mixture of non-opiate drugs. Research to date suggests that (unlike oral forms of the drug), long-acting naltrexone formulations are protective against opiate overdose. Also in Australia, adult and adolescent patients at high risk of overdose on oral naltrexone have been found to reduce their risk once implanted. Hospital records and deaths among the same set of adult patients were tracked for three and a half years following implantation, revealing a long-lasting reduction in opiate-related overdose and other admissions, counterbalanced somewhat in the first six months by an increase in admissions related to other drugs. Of the 384 Western Australian residents implanted during the two years of the study, just four had their implants removed, indicating a high level of acceptance of the procedure. Among 354 Includes 13 patients who transferred to implants following methadone treatment. of the same set of patients, there were no deaths in the first six months when the implants would have been active and eight over on average the following four years, of which at most five were or might have been drug-related, a death rate about the same as for methadone patients during the same period in the same area. Nevertheless, unless carefully managed (and perhaps even then) the transfer from an implant or depot preparation to oral naltrexone or non-medicated aftercare can still be a high-risk period for return to heroin and accidental overdose. Prescribing information for a depot injection licensed in the USA for the treatment of alcohol dependence warns that attempts to override the opiate blockade can be fatal, and that after treatment is discontinued patients accustomed to opiates may find they are now more sensitive to these drugs, increasing the risk that the doses they previously took could now be dangerous.
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