Hello Andrew, Thanks for posting your query, It is correct that there are doses of up to 150mg per pill but they all have specific indications and how to take doxipin. Treatment should be initiated with low doses with progressive increases only if required and tolerated, and the patients should be under close surveillance at all dosage levels. So you taking 4 pills at ones without doctor s advice is contraindicated. If you started at low dose of 10mg and increased gradually (while monitoring your tolerance level), you might not have experienced the chest pain. This drug should be taken (if for medical reasons) with advise of a doctor but if you are doping then taking high doses is at your own risk and I recommend you stop before any irreversible damage occurs. One of the serious side effects is heart attack (worst one is cardiac arrest hence death) especially when you had a previous heart diseases (chances of heart attack increases). Hope you consider my advise and wish you a better health. Dr. Nsah