A 21-year-old woman with a heart condition is dead after consuming a heavily caffeinated energy drink at Panera Bread that she may have believed was regular lemonade, her parents alleged in a wrongful death suit against the restaurant chain.

In September 2022, after drinking 鈥淐harged Lemonade,鈥 Sarah Katz experienced cardiac arrest while at a restaurant with friends and died after being transported to the hospital and suffering a second arrest, according to the lawsuit, which was filed Monday morning in Philadelphia.

Katz鈥檚 parents are seeking compensatory and punitive damages.

鈥淲e were very saddened to learn this morning about the tragic passing of Sarah Katz, and our hearts go out to her family,鈥 Panera told CNN in a statement. 鈥淎t Panera, we strongly believe in transparency around our ingredients. We will work quickly to thoroughly investigate this matter.鈥

In an autopsy report obtained by CNN, the medical examiner cites Katz鈥檚 cause of death as cardiac arrhythmia due to long QT syndrome (LQTS). LQTS is a disorder that can cause fast and irregular heartbeats that can be life-threatening, according to the Mayo Clinic.

Katz was diagnosed with LQTS when she was five years old, and managed symptoms by taking medication and limiting caffeine, the lawsuit states.

Most energy drinks contain large amounts of caffeine; added sugars; vitamins, such as B vitamins; and other legal stimulants. Panera鈥檚 鈥淐harged Lemonade鈥 includes sugar, caffeine, coffee extract and guarana extract, which are both sources of caffeine.

Health professionals have warned that young people who consume energy drinks can encounter dangerous side effects, such as dehydration, irregular heartbeat and heart failure. People with certain heart conditions could be more sensitive to the stimulating effects of these drinks, and could be more susceptible to adverse effects.

However, Katz was 鈥渞easonably confident it was a traditional lemonade and/or electrolyte sports drink containing a reasonable amount of caffeine safe for her to drink,鈥 the lawsuit says, adding that Panera misled consumers by not properly labelling 鈥淐harged Lemonade鈥 as an energy drink in stores.

鈥淚nstead, Defendants market, advertise, and sell Panera Charged Lemonade as a product that is 鈥楶lant-based and Clean with as much caffeine as our Dark Roast Coffee,鈥欌 the lawsuit reads. However, in their stores, Panera does 鈥渘ot specify what size of Panera Dark Roast coffee is akin to a Panera Charged Lemonade,鈥 making the comparison vague and 鈥渦nhelpful.鈥

Online, Panera says its 鈥淐harged Lemonade鈥 has a comparable amount of caffeine to its Dark Roast coffee. A large size, which comes in a 30-oz cup, contains about 390 mg of caffeine. The US Food and Drug Administration says that a safe quantity of caffeine 鈥渇or healthy adults鈥 typically amounts to about 400 milligrams per day (around four or five cups of coffee).

Additionally, the 鈥淐harged Lemonade鈥 is mixed 鈥渋n-house鈥 by store employees, meaning that 鈥渋ts caffeine content is not controlled and, in turn, has an innate and dangerous potential to vary,鈥 according to the lawsuit.

According to Elizabeth Crawford, the attorney representing Katz鈥檚 parents, Katz drank out of the large size cup. Katz had a Panera Sip Club membership that gives subscribers free in-store refills, so it鈥檚 not possible to know how much she drank, said Crawford.

鈥淲e want to make sure that the drink includes a warning, or is taken off the shelf,鈥 Crawford told CNN. 鈥淚t鈥檚 a dangerous energy drink and it鈥檚 not advertised that way. We want to make sure this does not happen to someone else.鈥