To the Editor: Gibson et al provide us with five cases of fatal drug overdose in an article titled “Opioid overdose deaths can occur in patients with naltrexone implants”.1
In one of these, the cause of death was combined non-opioid drug toxicity, including amphetamine and a cocktail of other drugs, where opioids were not present. Obviously, naltrexone, an opioid antagonist, will not protect against non-opioid drug overdose.
Clearly these four cases should never have been included under the title “Opioid overdose deaths can occur in patients with naltrexone implants” (our italics).
That leaves a single fatal opioid overdose in a patient who had an active implant, and in which the cause of death was acute narcotism, where the individual had injected heroin. Here at last is a case study that should be included, and the authors note that the effects of naltrexone can be overcome, and alert us to the danger of using excess heroin to overcome naltrexone blockade.
However, this information is less than new. MIMS annual notes under “Attempts to overcome [naltrexone] blockade”:
While . . . [naltrexone] is a potent . . . [opioid] antagonist . . . the blockade produced . . . is surmountable . . . [and] poses a potential risk to individuals who attempt, on their own, to overcome the blockade by administering large amounts of exogenous opioids. Indeed, any attempt by a patient to overcome the antagonism by taking opioids is very dangerous and may lead to a fatal overdose . . . Patients should be told of the serious consequences of trying to overcome the opiate blockade.2
It is also surprising that no denominator is attempted on the number of patients who may have received treatment by implanted naltrexone between 2000 and 2004. This information is available through the Therapeutic Goods Administration, and would have given the reader a clearer ability to evaluate the significance of this single case study. For example, one of the articles they cite reports one fatality in nearly 600 person-years of follow-up,3 giving a very different impression of risk compared with the article by Gibson and colleagues.
