Although available in Britain, it is only handed out with a prescription and strict instructions regarding its use.
Doctors use it to treat “moderate to severe” pain such as that following an operation or after serious injury.
Originally produced and marketed in Germany in the late 1970s, Tramadol is in use across the globe under brand names Invodol, Larapam and Mabron.
It is prescribed in the form of tablets, capsules, drops or as an injection.
Side effects include feelings of nausea and dizziness.
Tramadol’s addictive effects are similar to those of heroin and include feelings of warmth, wellbeing and drowsiness.
Earlier this year, I’m A Celebrity…Get Me Out Of Here! host Ant McPartlin sought rehab after taking the drug in a cocktail with morphine and alcohol.
NHS officials warn that it is possible to take controlled medicines abroad for personal use, but only if accompanied by an explanatory note from a doctor.
After Miss Plummer’s arrest, the Foreign Office updated its travel advice to holidaymakers heading for Egypt: “If you are travelling with prescription medication you should carry a medical certificate confirming that the medication has been prescribed for a medical condition.”