Heath Ledger was also taking antihistamines one of the mored overused drugs. Antipsychotic drugs are similar to antihistamines and were developed when it was noticed that paople in mental institutions became zonked out and passive on antihistamines. Longterm use of them causes Parkinson's disease.
He is reported to have had pneumonia,which is unusual in someone his age. I used to get pneumonia as a secondary infection after I had a cold or flu until I stopped taking OTC cold meds. Medications which suppress symptoms and prevent elimination of toxins cause more serious ilnesses.