How meaningful are studies that are stopped early?

Fenofibrate (e.g. LIPANTHYL) for type 2 diabetes?
Beta-blockers: only second line in hypertension?
Clopidogrel (ISCOVER, PLAVIX) and metoprolol (e.g. BELOC) in acute myocardial infarction

IDEAL-study: high-dose atorvastatin (SORTIS) not better than simvastatin (e.g. ZOCOR)

Is venlafaxine (TREVILOR) superior to other antidepressants?
Mistletoe (e.g. ISCADOR) and quality of life in cancer

Quality check: metoclopramide (e.g. PASPERTIN)
German "Sportbund": cachet for dietary supplements?

Depression with angiotensin II receptor antagonists like olmesartan (OLMETEC, VOTUM)

Oseltamivir (TAMIFLU): dangerous abnormal behaviour and suicides in children?
EVRA transdermal contraceptive: thromboembolism due to high estrogen levels?