After the arrest, Plummer signed a 38-page statement in Arabic that she thought would result in her being able to leave the airport, but instead she was transfered to a 15-ft by 15-ft cell with 25 other women and has been there for almost a month now.
He said his sister just thought she was doing a "good deed" by bringing the medication over to her husband, and said she will be "completely out of her comfort zone" in jail.
Tramadol has been illegal in Egypt since 2015, after it had become so popular that it replaced heroin and cannabis as the most popular recreational drugs.
Plummer visits her husband in Egypt at least four times a year. "She looked over at us and said "mum, mum, please help me, help me".
Ms Synclair said her sister is "naive and child-like" and "didn't even check what the drugs were".
"They say she's unrecognizable", her brother continued.
The 33-year-old Laura Plamer from the United Kingdom can be sentenced by Egyptian court to death for the found in her bag tramadol.
"She can't stay in there any longer or she will be murdered or kill herself".
She said her "naïve" sister travels out to see him between two and four times a year, according to the Mirror.
Ms Plummer was arrested after flying in to a Red Sea beach resort for a break with Omar. One lawyer has even mentioned the possibility of the death penalty. "But the conditions are going to be extremely basic and I'm sure she's petrified by what is unfolding before her".
Laura Plummer signed a statement in Arabic, believing she'd be able to leave the airport afterward and start her holiday.
Her brother went on to reveal that the family is feeling "helpless" and that she is "not a tough person at all". She is due to appear in the dock again on Thursday.
The last text message sent by the shop keeper was to her father, Neville, and said: 'I'm in trouble and I need your help'.
Tramadol, a strong painkiller, is legal in the United Kingdom but users must have a prescription.
He said that a British Embassy representative has been visiting Ms Plummer regularly and has been in touch with her family.