Naltrexone has not been shown to cause erectile dysfunction in controlled studies, and a small but provocative body of research suggests it may actually help with erections in some men. The confusion likely arises because naltrexone is prescribed to people recovering from opioid or alcohol dependence, and both of those conditions carry their own significant sexual side effects. Separating the drug’s influence from the underlying condition turns out to be the real challenge.
What Controlled Studies Actually Found
The most direct test of naltrexone’s effect on erections comes from a randomized, placebo-controlled trial of twenty men with erectile dysfunction that had no identifiable vascular or neurological cause. After eight weeks of naltrexone treatment, the men experienced a significant increase in early-morning erections compared to placebo, while libido and frequency of intercourse stayed about the same between groups.1PubMed. Opiate antagonists in erectile dysfunction: a possible new treatment option? Results of a pilot study with naltrexone That finding alone is striking: rather than impairing erections, the drug appeared to support them.
An earlier clinical study reinforced the same direction. Fifteen men with erectile difficulties were given naltrexone, and eleven of them showed improved sexual performance, with significant increases in both successful intercourse and spontaneous full erections per week. The researchers found no significant changes in luteinizing hormone, follicle-stimulating hormone, or testosterone, suggesting the benefit wasn’t hormonal but rather something happening in the brain.2PubMed. Endorphins in male impotence: evidence for naltrexone stimulation of erectile activity in patient therapy No significant side effects were reported.
These are small studies, and the field never followed up with large-scale trials. But the evidence that does exist points away from naltrexone causing ED and, if anything, hints at a therapeutic effect. So why do some men on naltrexone report sexual problems?
Why Sexual Dysfunction Rates Look High in Naltrexone Users
The numbers that fuel concern come mostly from surveys of people taking naltrexone for opioid dependence. One study comparing men on buprenorphine maintenance with men on naltrexone maintenance found that about 67% of the naltrexone group reported erectile dysfunction, along with high rates of premature ejaculation and reduced desire.3PubMed. Sexual dysfunction among male patients receiving buprenorphine and naltrexone maintenance therapy for opioid dependence Those numbers sound alarming until you consider the context: these were men recovering from opioid dependence, and the buprenorphine group had similarly high rates of sexual dysfunction. On a standardized sexual function questionnaire, the two groups were not significantly different from each other, despite taking pharmacologically opposite drugs (buprenorphine activates opioid receptors; naltrexone blocks them).
That pattern is a strong clue that the sexual problems are tied to the patient population, not the medication. Opioid dependence itself disrupts the hormonal and neurological systems involved in sexual arousal and performance. Recovery from chronic opioid use takes time, and sexual function is often among the slower things to return to normal. Attributing the ED to naltrexone when the comparison group on a completely different drug shows the same problem is a classic case of mistaking correlation for causation.
Alcohol, the Other Confounding Factor
The other large group of naltrexone users is people being treated for alcohol use disorder. Chronic heavy drinking is itself a well-established cause of erectile dysfunction. Long-term alcohol use damages the blood vessels and nerves involved in erections, disrupts hormone balance, and causes oxidative stress in the erectile tissue of the penis.4PubMed. Chronic ethanol consumption induces erectile dysfunction: Role of oxidative stress The damage involves increased reactive oxygen species in the erectile tissue and activation of a pathway that makes the smooth muscle less able to relax, which is the fundamental mechanical step behind getting an erection.
Reviews of sexual dysfunction in chronic alcoholism have documented high rates of impaired desire, arousal, and performance across endocrine, neurological, and psychological dimensions.5PubMed. Chronic alcoholism and male sexual dysfunction A man who starts taking naltrexone for alcohol dependence and notices erectile problems may be experiencing consequences of his drinking history, not a side effect of the pill he just started. Some of this damage can improve with sustained sobriety, but it doesn’t resolve overnight, and the early months of treatment are exactly when someone is most likely to blame the new medication.
How Blocking Opioid Receptors Affects the Sexual Brain
To understand why naltrexone might actually help rather than hurt erections, it helps to know what endogenous opioids do during sex. Your body releases its own opioids (endorphins and related peptides) during sexual activity, and these natural chemicals have a dampening effect on certain aspects of sexual response. In animal research, injecting an opioid that selectively activates the mu receptor caused rats to take much longer to ejaculate and to ejaculate fewer times overall. That inhibitory effect was completely reversed by pretreatment with an opioid blocker.6PubMed. Endomorphin-1, effects on male sexual behavior
Naltrexone works by blocking those same opioid receptors, particularly the mu receptor. In the brain’s reward circuitry, opioids normally inhibit dopamine signaling. Blocking opioid receptors with naltrexone can disinhibit dopamine neurons, effectively allowing more dopamine activity in circuits involved in motivation and arousal. Research in rats has shown that naltrexone administered into the ventral tegmental area, a key hub of the brain’s reward system, reversed sexual exhaustion in experienced animals by lifting the opioid-driven brake on dopamine.7PubMed. The mesolimbic system participates in the naltrexone-induced reversal of sexual exhaustion The effect depended specifically on mu-opioid receptors, not delta-opioid receptors, which aligns with naltrexone’s primary binding profile.
The interplay between opioids and dopamine in sexual function is genuinely complex. Opioids released during arousal and orgasm feed into reward and bonding pathways, and blocking them changes the dynamics of pleasure and motivation in ways that aren’t fully mapped out.8Sexual Medicine Reviews. Orgasms, sexual pleasure, and opioid reward mechanisms But the available animal data consistently shows that opioid blockade tends to facilitate or restore sexual behavior rather than impair it. That matches the human pilot data showing improved erections.
Naltrexone Combined With Antidepressants
One situation where men might worry about stacking sexual side effects is when naltrexone is prescribed alongside an antidepressant, which is common in addiction treatment. A study that specifically tested this question randomized veterans into four groups receiving different combinations of the antidepressants desipramine or paroxetine with either naltrexone or placebo. The researchers tracked reports of decreased sex drive and impotence at weekly visits. Adding naltrexone made no difference: there were no significant differences in sexual side effects between the naltrexone and placebo groups, regardless of which antidepressant they were taking.9PubMed. A Comparison of Sexual Side Effects of Antidepressants With and Without Naltrexone
Naltrexone also didn’t improve the antidepressant-related sexual side effects, which dashes a hypothesis some clinicians had floated. But the key finding for anyone worried about ED is that naltrexone didn’t add to the problem. If you’re on an antidepressant and also taking naltrexone, your sexual side effects are likely driven by the antidepressant, not the naltrexone.
Low-Dose Naltrexone and Sexual Function
Low-dose naltrexone (LDN), typically in the range of 1.5 to 4.5 milligrams daily compared to the standard 50-milligram dose, has developed a following for various off-label uses including autoimmune conditions, chronic pain, and multiple sclerosis. A randomized placebo-controlled trial of low-dose naltrexone in patients with multiple sclerosis measured quality of life across many domains, including sexual function. No meaningful difference appeared between the LDN group and the placebo group on sexual function measures.10Multiple Sclerosis Journal. The effect of low-dose naltrexone on quality of life of patients with multiple sclerosis: a randomized placebo-controlled trial
That’s a null finding, and null findings are easy to dismiss, but they carry real information. At the low doses used by people experimenting with LDN for inflammation or pain, there is no signal of sexual harm. The mechanism is different from full-dose naltrexone (LDN is thought to cause a brief, partial opioid blockade that leads to a rebound increase in endorphin production), but neither dosing strategy has been tied to erectile dysfunction in controlled settings.
When Naltrexone Compared Favorably
One head-to-head comparison that catches the eye involved patients with opioid use disorder receiving either extended-release naltrexone implants or sublingual buprenorphine/naloxone. The naltrexone implant group actually scored significantly better on a standardized sexual experiences scale than the buprenorphine/naloxone group, along with better scores on sleep quality and overall quality of life.11Addicta: The Turkish Journal on Addictions. A Comparison of Buprenorphine/Naloxone and Extended-Release Naltrexone Treatments in Terms of Sleep Quality, Sexual Life, Eating Behavior, and Quality of Life in Patients with Opiate Use Disorder
The researchers concluded that extended-release naltrexone may provide better sexual outcomes than buprenorphine-based treatment for opioid use disorder. This is consistent with what you’d expect pharmacologically: buprenorphine is a partial opioid agonist, meaning it activates opioid receptors to a degree, and chronic opioid receptor activation is well known to suppress testosterone and impair sexual function. Naltrexone, by blocking those receptors instead of activating them, avoids that particular problem.
Why People Still Believe Naltrexone Causes ED
The persistence of this belief comes down to a few converging factors. Drug information labels list sexual side effects that were reported during clinical trials without necessarily establishing that the drug caused them. If 10% of trial participants with alcohol dependence report ED over a 12-week trial, that number goes on the label regardless of whether the rate in the placebo group was similar. People understandably read the label and assume the drug is responsible.
Online forums amplify the signal. Someone who starts naltrexone and experiences ED posts about it; someone who starts naltrexone and has perfectly fine sexual function doesn’t post about it. The resulting sample is wildly skewed toward negative experiences. Add in the fact that most naltrexone users are dealing with substance use disorders that independently harm sexual function, and you have a recipe for a widespread but poorly supported belief.
There’s also a psychological dimension. Starting a new medication creates heightened body awareness, and performance anxiety around sex is both common and self-reinforcing. A man who expects a new pill to cause ED is more likely to experience difficulty, which confirms his expectation, which increases anxiety the next time. This nocebo effect is well documented across many classes of medication.
Genetic Variation and Individual Response
Not everyone responds to naltrexone in the same way, and genetics play a role. Research has identified that variations in the gene encoding the mu-opioid receptor (OPRM1), along with genes involved in dopamine signaling like the dopamine transporter gene (DAT1) and the catechol-O-methyltransferase gene (COMT), interact to predict how well naltrexone works for reducing heavy drinking.12PubMed Central. Opioid and Dopamine Genes Interact to Predict Naltrexone Response in a Randomized Alcohol Use Disorder Clinical Trial These same opioid and dopamine pathways are the ones involved in sexual arousal and response, so it’s biologically plausible that genetic makeup could also influence whether naltrexone has positive, negative, or neutral effects on a given person’s sexual function.
This research is in its early stages for sexual outcomes specifically, but it fits with the broader clinical observation that some men report feeling more sexually responsive on naltrexone while others notice no change and a minority feel something is off. The drug’s effects on the opioid-dopamine interaction are real, but the direction and magnitude depend on your individual neurochemistry. Blanket statements that naltrexone either causes or cures ED miss this person-to-person variability.
Practical Considerations if You’re Concerned
If you’ve been prescribed naltrexone and you’re worried about sexual side effects, a few things are worth keeping in mind. First, the controlled evidence leans toward naltrexone being sexually neutral or mildly beneficial, not harmful. Second, if you’re taking naltrexone for alcohol or opioid use disorder, those conditions themselves are far more likely culprits for any sexual difficulties than the medication is. Sustained recovery tends to improve sexual function over time as the body heals.
If you do notice changes after starting naltrexone, give it time. The early weeks of addiction treatment involve enormous physiological and psychological adjustment, and sexual function can fluctuate for reasons that have nothing to do with the drug. Track whether things improve over weeks rather than making a judgment in the first few days. If erectile difficulties persist and are genuinely new, a conversation with your prescriber can help sort out whether other medications, underlying health conditions, or psychological factors are more likely explanations. Stopping naltrexone because of a side effect it probably isn’t causing would be trading a real treatment benefit for a misattribution.
The Unfinished Science of Opioid Blockade and Erections
The pilot studies suggesting naltrexone could treat erectile dysfunction were published in the late 1980s and 1990s, and despite promising results, large confirmatory trials never materialized. The arrival of PDE5 inhibitors in the late 1990s effectively ended interest in alternative oral approaches to ED. Pharmaceutical companies had little incentive to fund expensive trials for a generic opioid antagonist when a blockbuster class of drugs was already dominating the market.
That leaves the field in an awkward position. The mechanistic logic is sound: blocking opioid receptors disinhibits dopamine in reward and arousal circuits, and animal models consistently show that opioid antagonism facilitates sexual behavior. The small human trials were positive. But the definitive proof that would turn naltrexone into an accepted ED treatment simply doesn’t exist, and probably never will. For the narrower question this article set out to answer, though, the evidence is fairly clear. Naltrexone has not been shown to cause erectile dysfunction in any controlled comparison against placebo. The drug remains one of the more sexually benign medications in the psychiatric and addiction pharmacopoeia.