Naltrexone for Cocaine: Efficacy in Addiction Treatment

Naltrexone, a medication best known for treating alcohol and opioid dependence, has shown only inconsistent results when tested against cocaine addiction on its own. No medication is currently approved by the FDA specifically for cocaine use disorder, and naltrexone has not broken through that barrier despite decades of study. The story is more complicated than a simple pass-or-fail verdict, though, because certain patient subgroups and certain drug combinations involving naltrexone have produced genuinely encouraging signals in clinical research.

Why an Opioid Blocker Would Matter for a Stimulant

Cocaine is a stimulant, not an opioid, so the idea of prescribing an opioid receptor blocker to treat cocaine addiction can seem counterintuitive. The rationale rests on the fact that the brain’s own opioid system, sometimes called the endogenous opioid system, is deeply intertwined with the reward circuitry that cocaine hijacks. When someone uses cocaine, the resulting flood of dopamine does not happen in isolation; endogenous opioid peptides are also released and contribute to the reinforcing “high.” Blocking those opioid receptors with naltrexone could, in theory, weaken the reward signal that keeps a person coming back to the drug.

Animal studies have provided the clearest evidence for this connection. In rats trained to self-administer cocaine, naltrexone injected directly into the ventral tegmental area, a key hub of the brain’s reward pathway, reduced how much cocaine the animals took. The same effect was not seen when naltrexone was delivered to other brain regions like the nucleus accumbens or prefrontal cortex, suggesting the drug’s anti-cocaine action targets a specific circuit rather than blunting reward broadly.¹ Separately, research on rats that had been abstinent from cocaine showed that naltrexone reduced cue-triggered cocaine-seeking behavior, providing the first evidence that the opioid system is involved in how environmental cues pull a person back toward cocaine after they have stopped using it.²

The biology, in other words, is plausible. The question is whether that biological plausibility holds up when you move from a rat pressing a lever to a human navigating real-world triggers, stress, and the complexities of addiction.

What Clinical Trials Show When Naltrexone Is Used Alone

The short answer is that the clinical evidence is underwhelming for most people. In the majority of randomized trials, oral naltrexone at standard doses has not reliably beaten placebo in reducing cocaine use among broadly defined groups of cocaine-dependent individuals. The signal is weak enough that no regulatory body has approved naltrexone for this purpose.

One trial stands out as a partial exception. Eighty-five participants who had already achieved initial abstinence were randomized to naltrexone (50 mg) or placebo, each paired with either relapse prevention therapy or standard drug counseling. Over twelve weeks, the group receiving both naltrexone and relapse prevention therapy had fewer cocaine-positive urine tests than the other three groups.³ The finding is notable because it suggests naltrexone may work best when combined with a specific behavioral framework, not as a standalone pill. A small pilot study comparing naltrexone plus cognitive behavioral therapy against CBT alone also found that the naltrexone group had fewer cocaine-positive urine screens and lower craving scores.⁴

These results are interesting but far from definitive. The studies are small, and the benefits appeared only in specific treatment pairings. For most clinicians, the takeaway is that naltrexone alone, handed to a patient without a structured behavioral program, is unlikely to make a meaningful difference in cocaine use.

The Alcohol Connection

A large proportion of people with cocaine use disorder also drink heavily, and since naltrexone is already an established treatment for alcohol dependence, researchers have naturally wondered whether it could address both problems at once. Results here are a mixed bag, and the direction of the findings depends heavily on the dose, the formulation, and who is in the study.

An early open-label study treated patients dependent on both alcohol and cocaine with 150 mg of oral naltrexone per day, three times the usual dose for alcohol treatment. Participants showed a statistically significant reduction in both the percentage of days they used cocaine and the amount of money spent on it.⁵ That was encouraging, but it was a small, uncontrolled study without a placebo group.

A larger controlled trial tested the same high dose of 150 mg daily in cocaine-and-alcohol-dependent patients, this time with a placebo comparison and structured therapy. Naltrexone reduced heavy drinking days, as expected, but the probability of cocaine-positive urine samples did not differ between the naltrexone and placebo groups overall.⁶ A pilot trial of injectable extended-release naltrexone in a similar population also found no advantage over placebo for cocaine or alcohol use over eight weeks.⁷

Reading these studies side by side, a pattern emerges. When you look at the overall group, naltrexone does not clearly reduce cocaine use in people with dual cocaine and alcohol dependence. But when you start breaking the results down by subgroup, things get more interesting, especially by gender.

Gender Differences in Response

One of the more striking findings in the naltrexone-for-cocaine literature is a sex difference that held up across multiple analyses. In the high-dose (150 mg/day) trial mentioned above, researchers found a significant interaction between gender and medication response. Men taking naltrexone showed reductions in both cocaine and alcohol use compared to men on placebo. Women, by contrast, actually had higher rates of cocaine and alcohol use on naltrexone than women on placebo.⁸

A follow-up analysis tried to figure out what was driving this gap. In men, none of the pre-treatment characteristics measured predicted who would drop out of treatment. In women, though, those with severe pre-treatment psychiatric symptoms or who experienced nausea as a side effect were significantly more likely to stop taking the medication.⁹ Nausea is one of naltrexone’s most common side effects and can be worse at higher doses. If women are more likely to stop treatment because of it, any potential benefit never has time to appear.

These findings are preliminary, drawn from a single trial with secondary analyses, and should be treated cautiously. But they illustrate a broader point about addiction pharmacotherapy: “does the drug work?” is often the wrong question. The more useful question is “for whom does it work, and under what conditions?” Naltrexone for cocaine may eventually turn out to be a medication that benefits a definable subgroup rather than the population at large.

Combination Strategies

Given naltrexone’s modest track record as a standalone therapy for cocaine, researchers have shifted attention toward combinations that pair it with other medications. The most developed of these involves buprenorphine, a partial opioid agonist widely used in opioid addiction treatment. The pairing sounds paradoxical: why combine an opioid blocker with an opioid activator? The logic is that buprenorphine at low doses modulates the reward system in a way that reduces cocaine’s appeal, while naltrexone prevents buprenorphine from producing opioid dependence.

In rodent studies, buprenorphine alone reliably decreased cocaine self-administration. Adding a low dose of naltrexone preserved that anti-cocaine effect specifically in rats with compulsive cocaine-taking patterns, while also preventing the physical withdrawal symptoms that buprenorphine alone caused. The combination appeared to selectively target compulsive use without simply dulling all motivation.¹⁰

This preclinical work led to the CURB trial (Cocaine Use Reduction with Buprenorphine), a multi-site human study. In people who met criteria for cocaine dependence and also had current or past opioid problems, buprenorphine-naloxone combined with naltrexone was associated with reductions in cocaine use compared to placebo.¹¹ The important caveat is that this population had co-occurring opioid issues, so the results may not generalize to people who use cocaine alone. A follow-up trial, CURB-2, is now testing injectable extended-release formulations of both naltrexone and buprenorphine, partly to address adherence issues with daily pills.¹²

Another combination explored in animal models pairs naltrexone with amphetamine. In rhesus monkeys trained to choose between cocaine and food, a dose of naltrexone that had no effect on cocaine choice by itself enhanced the ability of a low dose of amphetamine to shift the animals toward choosing food instead of cocaine. The amphetamine dose used was low enough that it did not produce the kind of nonselective behavioral disruption seen at higher doses, and naltrexone seemed to sharpen its anti-cocaine effect while preventing some of its side effects.¹³ This is still strictly preclinical, but it offers one more proof of concept that naltrexone’s value in cocaine treatment may lie in how it modifies the action of another drug rather than how it works on its own.

A separate approach pairs naltrexone with bupropion, a medication already approved for smoking cessation and depression. A fixed-dose combination of naltrexone and bupropion (marketed as Contrave for weight loss) has been explored for cocaine use disorder in at least one clinical case. The rationale is that naltrexone’s opioid blockade and bupropion’s effects on dopamine and norepinephrine could jointly address the reward pathways driving cocaine use.¹⁴ Case reports are the lowest tier of clinical evidence, so this is worth watching rather than acting on, but it represents yet another angle for combination treatment.

Why Genetics May Determine Who Responds

The inconsistency of naltrexone’s results across trials has pushed some researchers toward a pharmacogenomic question: maybe the drug works, but only in people with certain genetic profiles. Since naltrexone acts on opioid receptors, genetic variation in the genes encoding those receptors could plausibly affect whether the medication does anything useful for a given individual.

One line of evidence involves the kappa opioid receptor gene, OPRK1. Certain variants of this gene are associated with higher stress-induced cocaine craving, stronger cortisol responses to stress, and a greater risk of relapse. In one study, individuals carrying a specific OPRK1 variant had significantly higher stress-induced craving and were more likely to return to cocaine use.¹⁵ Naltrexone has some antagonist activity at kappa receptors, which raises the possibility that people with these variants could respond differently to the medication, though that link has not been tested directly in a clinical trial.

Another gene of interest is OPRM1, which encodes the mu-opioid receptor, naltrexone’s primary target. Variants in OPRM1 have been shown to influence cocaine self-administration behavior in animal models. Mice carrying certain OPRM1 variants showed greater cocaine intake, along with altered gene expression in brain regions involved in reward processing.¹⁶ If the human equivalent of these variants similarly modifies how someone responds to naltrexone, it could explain why trials that lump all participants together tend to wash out. Some people might be getting a genuine benefit that gets diluted by the non-responders in the same study.

This kind of precision medicine approach is still in its early stages for cocaine use disorder. No genetic test currently exists that would tell a clinician whether to prescribe naltrexone for a particular patient with cocaine addiction. But the direction of the research suggests that future trials might be more successful if they pre-select participants based on genetic markers rather than treating everyone the same.

The Adherence Problem

One factor that haunts every naltrexone study, whether for opioid, alcohol, or cocaine use disorder, is medication adherence. Naltrexone does not make you feel good. It blocks the brain’s opioid receptors, which means it can subtly dampen the experience of natural pleasures on top of blocking drug-induced reward. Many patients simply stop taking it. In the gender-difference analyses described earlier, women were especially prone to dropping out because of nausea, but men also stopped treatment at significant rates.⁹

Injectable extended-release naltrexone, given as a monthly shot, partly solves this by removing the daily decision of whether to take a pill. Once the injection is administered, the medication is active for about four weeks regardless of whether the person would have chosen to keep taking it. This is why the CURB-2 trial specifically chose injectable formulations for both naltrexone and buprenorphine.¹² However, even injectable formulations require the person to show up for the injection appointment. And the pilot trial of injectable naltrexone for co-occurring cocaine and alcohol dependence did not show a benefit over placebo, so the delivery method alone is not a magic fix.⁷

Adherence matters because it muddies the interpretation of every negative trial. When a study reports that naltrexone did not beat placebo, it is hard to know whether the drug truly does not work or whether too many participants stopped taking it for the drug to have a fair shot. This is a challenge across addiction medicine, but it is especially acute with naltrexone because the medication offers no immediate subjective reward to motivate continued use.

How Naltrexone Compares to Other Pharmacological Options

Naltrexone is far from the only medication that has been tried for cocaine use disorder. Disulfiram, traditionally used for alcohol dependence, has shown some promise in reducing cocaine use, possibly through its effect on dopamine metabolism. In the small pilot trial comparing disulfiram and naltrexone, both medications paired with CBT outperformed CBT alone in reducing cocaine-positive urine tests, with disulfiram and naltrexone performing comparably.⁴ Topiramate, modafinil, and various dopamine-targeting agents have also been tested, mostly with similarly mixed results. The broader reality is that cocaine use disorder remains one of the hardest addictions to treat pharmacologically, and no single drug has emerged as clearly effective across the general population.

Behavioral treatments remain the backbone of cocaine addiction care. Contingency management, where patients receive tangible rewards for drug-free urine samples, has the strongest evidence base of any intervention for cocaine use disorder. Cognitive behavioral therapy also has solid support. The most realistic near-term scenario for naltrexone in cocaine treatment is not as a replacement for these approaches but as an add-on that might boost their effectiveness for the right patient, particularly men with co-occurring alcohol problems who can tolerate the medication and who are engaged in structured behavioral treatment.

Off-Label Prescribing in Practice

Despite the lack of FDA approval for cocaine use disorder, some addiction medicine specialists do prescribe naltrexone off-label to patients who use cocaine, especially when those patients also have alcohol use disorder, which is approved. Since naltrexone is already indicated for alcohol dependence, a clinician treating someone who drinks heavily and uses cocaine may prescribe it with the primary justification being the alcohol problem, while hoping it also helps with the cocaine. This is common and legal, though it puts the clinician in the position of relying on limited evidence for the cocaine component.

At the higher dose of 150 mg sometimes studied in trials, the off-label nature becomes more pronounced, since the standard approved dose for alcohol dependence is 50 mg daily. Higher doses carry a greater risk of liver enzyme elevations and gastrointestinal side effects, and patients need monitoring accordingly. Anyone being prescribed naltrexone at any dose should not be taking opioid medications, as the combination can trigger acute withdrawal. This is relevant to cocaine-using populations because many people who use cocaine also use opioids, and the interaction can be dangerous if not properly managed.