You are a final year medical student on an Emergency Medicine attachment. Dr. Kyriacou is your supervisor. 

Mattias Garcia, a 62-year-old man presents to the Emergency Department with his wife, complaining of diffuse muscle pain and severe muscle weakness, which started about 24 hours ago. You take a short history and establish that he was diagnosed with hypertension three years ago and dyslipidaemia a year ago. He is currently taking hydrochlorothiazide, simvastatin and low-dose aspirin. Mr Garcia is obese, and you ask about his diet. He tells you that he has recently started a new diet, the so-called grapefruit diet, which he heard was effective for weight loss. 

Investigations show elevated creatine kinase and creatinine, which is in line with the diagnosis you suspected. Dr. Kyriacou asks you to explain what has happened. 

What is the most likely explanation?