The Batman is full of Easter eggs and clues for potential sequels. One moment towards the end of the movie has sparked a lot of discussions. With Batman seemingly down for the count, he musters his last bit of energy and injects himself with a vial of bright green liquid. It gives him immediate energy and strength. He saves Catwoman but loses control and has to be held back from killing her assailant. But what serum did Batman inject himself with in The Batman? Could he have used simple adrenaline? Here’s why we suspect it’s something more—an early version of a drug from the Batman universe, Venom.

Real-life substances like adrenaline have some similar properties to Batman’s mystery compound, but this serum seems to be something else. In certain comic stories, Bane uses as a strength serum called Venom, and a precursor to this substance seems the most likely answer for Batman’s injection. For one, adrenaline is colorless and Batman’s drug is bright green. The movie has very little color in it at all, indicating that director and co-writer Matt Reeves add color to Batman’s injected serum for a reason.

The drug Venom from the Batman & Robin movie
Warner Bros.
 What Is Adrenaline? How Does It Compare to Batman‘s Venom

Also, called epinephrine, adrenaline is a natural hormone. The human body releases more of it in stressful situations, thus the term adrenaline rush. This increases blood sugar levels, which results in more energy. Heart rate also increases. The muscles around the lungs and airway relax, making it easier to breathe. This combination prepares the body for physical activity, whether you choose the fight or the flight response. Of course, unlike what we saw in The Batman after Bruce Wayne injected himself, super-strength and berserker rage are not known side effects.

Synthetic adrenaline, like that in an EpiPen, has the same effect on the body. The pre-loaded syringe injects 0.3 milliliters of epinephrine, equal to 1/16 of a teaspoon or roughly 6 drops. Severe asthma or allergies that cause anaphylaxis can narrow a person’s airway, making it hard or impossible to breathe. Epinephrine opens the airways. Both natural and synthetic adrenaline can be fast-acting. Think of the way your heart pounds when you narrowly avoid a traffic accident, or when watching a scary movie. But the full effects take a few minutes to kick in. So it’s unlikely that a dose of adrenaline alone would allow anyone to leap into immediate action like Batman did after injecting himself with his serum, again hinting there is something more at play.

Epinephrine also only lingers in your system for a short time. If someone is in anaphylactic shock, one dose isn’t always enough to get them back to normal. Once someone gets an EpiPen injection, they should still get medical attention. They may require more doses. And they will certainly need time to recover.

A Serum Shot for Batman’s Heart

Another use of adrenaline is to treat an irregular heartbeat, sometimes due to blunt force trauma. Batman is shot at close range by a shotgun. Even when wearing body armor, he could be severely injured. Cardiac concussions can happen in car accidents and sports injuries. When a person gets hit in the chest it can cause a disruption to the heart’s rhythm, breathing problems, and even a heart attack. This is diagnosed with an EKG or treated in the field with an AED (automated external defibrillator).

There are often AEDs in public areas. There is likely one present somewhere in Gotham Square Garden, but probably not above the stage where this scene took place. Two pads placed on the skin check heart rate and apply electricity if needed. How long would it take to get Batman out of the suit? It is good he had this injectable option in this case but perhaps going forward, he should have an AED built into his suit. Venom (if that’s what Batman’s serum is) also has many more adverse side effects than an AED.

A shot of adrenaline can shock the heart into its normal rhythm. At hospitals, the dosage is 1 milliliter given intravenously rather than straight to the heart. Like in Pulp Fiction, if there’s no time to set up an IV line, an injection into the heart can save someone.

Warner Bros.
 Venom or Adrenaline, The Batman‘s Serum Could Become Addictive

Batman‘s Venom is highly addictive. As for adrenaline, small studies of sky-divers and rock-climbers found that the activities have addictive qualities. So-called adrenaline junkies even show withdrawal symptoms when they’re not engaged in a risky activity. Repeated stress cycles have negative effects. The fight or flight response is trigged in small ways nearly every day. Activities like waiting until the last minute to meet a deadline or picking fights in the comments section are more subtle ways to get a rush of adrenaline.

People at risk of severe allergies or asthma attacks carry EpiPens wherever they go. Those at risk of cardiac events often have an AED in their home. Batman carrying his own treatment is probably smart considering the risk. Dosing that with other chemicals to make the effects more immediate or last longer is a logical step for him. It is a slippery slope and one we may see on-screen if Batman becomes addicted to the mysterious serum. Or a villain, such as Bane, uses it for their own purposes.

Batman is certainly not the first comic book character to tinker with potentially dangerous substances. Or rush human trials. Because The Batman is not an origin story, we don’t get to see the R&D phase for Batman’s gadgets, serums, or any other contraption. The Batman‘s surprise reveal of this vial of green liquid serum sparked debate and leaves us with a lot of questions.