standard dose of disulfiram reported
significantly fewer drinking days than their
peers over the course of a year.^140 One
explanation for the variation in effectiveness
may be related to addiction severity: those with
more severe addiction may drink despite the
adverse reactions caused by disulfiram, or avoid
taking the medication altogether.^141
Naltrexone, used in the treatment of addiction
involving alcohol and opioids, blocks opioid
receptors in the brain, leading to reductions in
the reinforcing effects of these drugs.^142 It does
this by disrupting the transmission of dopamine-
-and thus the endorphin rush--caused by alcohol
and opioid ingestion.^143
Oral naltrexone (brand names ReVia and
Depade), which is available as a daily tablet,
was approved by the FDA to treat addiction
involving alcohol in 1984. Injectable naltrexone
(brand name Vivitrol), which is an extended
release monthly deep intramuscular gluteal
injection,* 144 was approved by the FDA in 2006
for addiction involving alcohol and in 2010 for
the treatment of addiction involving opioids.^145
Naltrexone is prescribed for patients who have
not ingested opioids for seven to 10 days
because it can cause serious withdrawal
symptoms if used at the same time as an
opioid.^146
Because of naltrexone’s mechanism of action—
reducing the reward or “high” associated with
substance use-- some patients may not take the
medication regularly.^147 Noncompliance also
may be associated with experiencing
uncomfortable side effects† at the start of a
course of treatment.^148 Unless participants
adhere to their treatment regimen 70 to 90
percent of the time,‡ naltrexone does not
produce significant outcomes.^149 Injectable
- When injected, the pharmacological agent releases
its active compound in a consistent way over a long
period of time.
† Side effects can include gastrointestinal problems
such as nausea, vomiting and abdominal pain and
central nervous system-related symptoms such as
headache and fatigue.
‡ The necessary adherence rate varies by the duration
of treatment.
naltrexone provides two advantages which may
improve retention and success rates: the need
for a monthly injection rather than a daily pill
and the need for regular contact with medical
and other supporting staff in the course of a
clinic visit which is required to obtain the
medication.^150 A disadvantage of the injection
formulation, however, is that it has more side
effects at higher doses.^151For addiction involving alcohol, the medication
is more effective at reducing heavy drinking
than increasing abstinence rates.^152 Several
randomized, placebo-controlled trials found that
compared to patients taking placebos, patients
taking naltrexone report significantly fewer
drinking days, fewer drinks per drinking day,
reduced cravings and reduced relapse.^153Because naltrexone blocks the euphoric effects
of opioids and does not produce a high when
taken, there is much less potential for misuse or
diversion than there is for other pharmaceutical
treatments, such as methadone, for addiction
involving opioids.^154 In one randomized,
controlled study, patients with addiction
involving heroin who received naltrexone
injections were significantly likelier to have
remained in treatment over the course of the
study than patients receiving a placebo
injection.§ 155 Buprenorphine,** when added to
naltrexone, has been found to improve retention
in treatment.^156 Relapsing to the use of opioids
after beginning naltrexone treatment can
increase patients’ risk of overdosing, due to
naltrexone’s effect on increasing the sensitivity
of opioid receptors in the brain to the effects of
opioids.^157Varenicline (brand name Chantix) is an effective
therapy for smoking cessation that works by
reducing the rewarding effects of nicotine
among patients who smoke while on the
medication and by reducing the craving and
withdrawal symptoms that occur among
abstinent patients.^158§ Naltrexone patients also were less likely than
placebo patients to test positive for cocaine,
benzodiazepine, marijuana and amphetamine use.
** See page 101.