Side Effects of Cabenuva: Injection Site Reactions and Risks

Injection-site reactions are by far the most common side effect of Cabenuva, the long-acting injectable combination of cabotegravir and rilpivirine used to treat HIV-1. Beyond soreness at the injection site, people may experience fever, fatigue, and headache, though most who try the regimen report that these effects are manageable and preferable to daily pills. The side-effect profile is generally well tolerated, but the drug’s unusually long residence in the body creates some unique considerations that don’t apply to oral HIV medications.

Injection-Site Reactions Are the Headline Side Effect

If you’ve read anything about Cabenuva, you’ve probably heard about injection-site reactions. They are the most frequently reported adverse event in both clinical trials and post-marketing surveillance. Pain at the injection site tops the list, followed by injection-site nodules, meaning small lumps under the skin that can persist for days or sometimes weeks after the shot.¹ Swelling, redness, and warmth at the injection site also occur. Cabenuva involves two separate intramuscular injections given in the gluteal muscle (one for each drug), so both injection sites can be affected.

The intensity of these reactions varies. In clinical trials, most injection-site pain was rated as mild to moderate, and it typically resolved within a week. In the ECLAIR trial, injection-site pain rated as moderate or worse was the most frequently reported adverse event, yet few participants actually discontinued treatment because of it.² Many people report that the discomfort lessens with subsequent injections, as the body adapts to receiving the drug in muscle tissue. Applying a warm compress afterward and moving around gently can help, though the soreness is hard to avoid entirely.

Systemic Side Effects Beyond the Injection Site

Cabenuva can cause side effects that have nothing to do with where the needle goes in. The most commonly reported systemic effects in clinical trials include pyrexia (fever), fatigue, and headache.³ These tend to show up within the first day or two after an injection and resolve on their own, often within 24 to 48 hours. Some people describe it as feeling like they’re coming down with a mild flu that passes quickly.

Depression has also appeared as a frequently reported event in post-marketing surveillance data, based on adverse event reports submitted to the FDA’s reporting system.⁴ It’s worth noting that depression is common in people living with HIV regardless of which medication they take, so pinning it specifically on Cabenuva is tricky. Still, if you notice new or worsening mood symptoms after starting the injections, it’s worth raising with your healthcare provider. In case reports of patients with kidney failure who switched to Cabenuva, no increases in depression, insomnia, headache, rash, or other systemic effects were observed.⁵

Weight Gain and Metabolic Changes

Weight gain is a hot topic with several classes of HIV medications, and people understandably want to know whether switching to Cabenuva will affect their weight or metabolic health. The evidence here is reassuring. A review of clinical trials found that average weight gain was modest, roughly one to two kilograms over 48 to 96 weeks, with no meaningful impact on blood sugar or cholesterol levels.⁶

A head-to-head comparison against a common oral regimen (bictegravir/emtricitabine/tenofovir alafenamide) produced even more encouraging numbers. People receiving Cabenuva had a median weight change of about half a kilogram lost, while those on the oral regimen had essentially no change. Waist circumference, hip circumference, and markers of metabolic syndrome and insulin resistance showed no clinically relevant shifts in either group.⁷ In practical terms, Cabenuva does not appear to drive the kind of weight gain that has been associated with some integrase inhibitors when used in oral form. If you’ve been worried about metabolic side effects specifically, Cabenuva looks neutral to mildly favorable compared to many daily pill options.

Drug Interactions Worth Knowing About

Because Cabenuva is an injectable that stays in your system for weeks, drug interactions matter in a way that’s harder to manage than with pills. If a daily oral medication causes a bad interaction, you can stop taking it and the drug clears your body in hours or days. With Cabenuva, you can’t un-inject it. Once the drug is deposited in your muscle, it slowly releases over weeks, and there’s no practical way to speed that up.

The most important drugs to avoid are those that strongly induce certain liver enzymes, because they can lower cabotegravir and rilpivirine levels enough to cause the drugs to stop working. Contraindicated medications include rifamycins (used for tuberculosis), the seizure medications carbamazepine and phenytoin, the antibiotic flucloxacillin, and the antifungal griseofulvin.⁸ The concern isn’t just a temporary dip in drug levels. Subtherapeutic concentrations can lead to virologic failure and potentially allow the virus to develop resistance to the drugs, which could limit future treatment options.⁹

The tuberculosis interaction is particularly relevant in parts of the world where both HIV and TB are common. Rifampicin, a cornerstone of TB treatment, is one of the strongest enzyme inducers known. Anyone being considered for Cabenuva needs a careful review of all their medications, including supplements and over-the-counter drugs, before the first injection. This isn’t unique to Cabenuva, but the inability to quickly reverse the injection makes it more consequential.

The Long Tail Phase and What It Means for You

One of the most unusual aspects of Cabenuva is how long the drugs linger in your body after you stop getting injections. Cabotegravir has a very long apparent half-life. In a study of HIV-uninfected adults, the average terminal half-life was about 45 days in males and 60 days in females.¹⁰ That means it takes months, not days, for the drug to leave your system after the last injection.

The median time for cabotegravir to become undetectable was roughly 44 weeks after the last injection in males and about 67 weeks in females. Body mass also played a role: people with a higher BMI tended to clear the drug more slowly.¹¹ Some individuals had detectable drug levels for well over two years after their last injection.

This matters for side effects in two ways. First, if you develop an adverse reaction to Cabenuva, you can’t just stop taking it and have the drug leave quickly. Any side effects caused by the drug itself will persist until levels drop sufficiently, which could take weeks or months. Second, the long tail creates a period where drug levels are present but declining, meaning they may be too low to suppress the virus yet too high to ignore. For people living with HIV, this creates a window of risk for developing drug resistance if they stop Cabenuva without bridging to an oral regimen. The tail phase isn’t a “side effect” in the traditional sense, but it shapes how every other side effect needs to be managed.

Staying on Schedule

Cabenuva is given either every month or every two months, depending on the formulation. Missing or significantly delaying an injection isn’t like forgetting a pill for a day. Because the drug is slowly released from a depot in the muscle, a late injection means drug levels may dip below what’s needed to keep the virus suppressed. In one real-world study tracking patients over 44 months, about 84 percent of injections were given on time, but 82 percent of patients experienced at least one delay, with a median delay of 10 days.¹²

In clinical trials, participants showed up on schedule more reliably, which is typical of controlled trial settings. The real-world data suggest that life gets in the way: scheduling conflicts, clinic availability, illness, travel. While the drug’s long half-life does provide some buffer, delays still carry risk. Product-dose omission and inappropriate scheduling were among the most common implementation-related issues flagged in post-marketing safety reporting.¹³ These aren’t side effects of the drug itself, but they are side effects of the delivery model, and they matter for outcomes.

Safety During Pregnancy

Data on Cabenuva in pregnancy are still being gathered, and the honest answer is that we don’t have enough information yet to draw firm conclusions. Animal studies have not shown reproductive toxicity or birth defects, which is encouraging but not definitive. The Antiretroviral Pregnancy Registry tracks birth outcomes in women exposed to cabotegravir, but the number of first-trimester exposures reported so far has been too small to calculate reliable risk estimates.¹⁴

In one large study that tracked nearly 500 confirmed pregnancies, adverse pregnancy outcome rates among those exposed to cabotegravir during pregnancy were similar to background rates and to rates among those not using the drug. Two major congenital anomalies were observed in the cabotegravir-exposed group (omphalocele and trisomy 21), neither of which was considered related to the drug.¹⁵ Still, the long tail phase adds a wrinkle. Because cabotegravir remains detectable for many months after the last injection, someone who stops Cabenuva before becoming pregnant may still have the drug in their system during early pregnancy. This isn’t an immediate cause for alarm given what animal studies and the available human data show, but it means pregnancy planning conversations need to happen well in advance of discontinuing the injections.

How People Actually Feel About the Trade-Off

Side-effect lists can make any medication sound alarming, so it helps to zoom out and ask how the people taking Cabenuva actually experience it. The consistent finding across multiple studies is that the large majority of users prefer the injections to daily pills, even with the injection-site discomfort. In the ECLAIR trial, about three-quarters of participants who received consecutive injections said they preferred the long-acting injection over oral medication, roughly the same proportion reported overall satisfaction, and 87 percent said they would recommend the therapy to others.¹⁶

A systematic review of patient-reported outcomes across clinical trials echoed these results. Most participants found injection-site reactions manageable and did not consider them a reason to stop treatment. The prevailing sentiment, as one participant in the LATTE-2 trial put it, was that the injection “hurts a bit, but it’s nothing compared to the relief I feel from not having to take pills every day.”¹⁷ For many people, the psychological benefit of not dealing with a daily pill, and not having a visible pill bottle that might prompt unwanted questions about their HIV status, outweighs the temporary physical discomfort of an injection every month or two.

Adolescents and Ongoing Research

Most of the safety data for Cabenuva come from studies of adults. Whether the side-effect profile is the same in younger people is being actively investigated. A large ongoing trial called LATA is evaluating Cabenuva in adolescents aged 12 to 19 in several African countries, comparing it to daily oral treatment over 96 weeks.¹⁸ Results from this trial will fill a significant gap, since adolescents face particular challenges with daily medication adherence and may also metabolize drugs differently than adults.

Adolescents living with HIV often struggle with stigma, privacy concerns, and the burden of lifelong daily treatment. If the side-effect profile in younger people turns out to mirror what’s been seen in adults, long-acting injections could meaningfully improve both adherence and quality of life in this group. But until the data are in, the safety profile in anyone under 18 remains an open question. Providers are prescribing Cabenuva to older adolescents in some clinical settings, typically weighing the known adult data against the individual patient’s circumstances, but it’s not yet standard practice for this age group.

When Cabenuva Might Not Be the Right Fit

The side-effect profile alone doesn’t tell you whether Cabenuva is appropriate for someone. Several clinical situations make the drug a poor fit regardless of tolerability. You need to be virally suppressed on your current oral regimen before switching, which means Cabenuva isn’t a first-line option for someone just starting treatment. Your virus also needs to lack certain resistance mutations to rilpivirine or cabotegravir, since the injectable format leaves no room for quick switches if resistance emerges.

People who take medications that are contraindicated with Cabenuva, like the anti-TB and anti-seizure drugs mentioned earlier, cannot use the regimen at all. And for anyone who may need to start one of those medications on short notice, the long tail phase creates a planning headache, since cabotegravir and rilpivirine will be present in the body for months after the last injection and could interact with newly added drugs during that time.

Reliability of clinic visits is another practical consideration. If your life circumstances make it difficult to show up for injections on a predictable schedule, the risk of missed or delayed doses and the potential for resistance development may outweigh the convenience of not taking daily pills. Cabenuva exchanges one type of adherence challenge (remembering a pill every day) for another (keeping regular clinic appointments), and neither is universally easier. The best candidates for the regimen tend to be people who are already virally suppressed, have no major drug interactions, and have reliable access to a clinic that can administer the injections on schedule.