Tramadol Administration
The tramadol (as Zydol fast-acting soluble 2 × 50 mg tablets) was dispensed by the pharmacy department at the Medway Maritime Hospital. An unblinded investigator dissolved the dose in an opaque water bottle with 100 mL water, before passing this to the researchers administering the test protocol. This dose has previously been shown to induce an effect on µ-opioid receptors, is well-tolerated (