Drug safety relates to the potential for adverse effects related to the administration of drugs. Efforts to establish the safely profile of drugs begin early in their development, with in vitro and in vivo toxicity testing, and continue through clinical trials leading up to drug approval and following approval in specific post-marketing studies or general pharmacovigilance efforts. Information received from patients and healthcare providers via pharmacovigilance agreements (PVAs), as well as other sources such as the medical literature, plays a critical role in providing the data necessary for pharmacovigilance to take place. In fact, in order to market or to test a pharmaceutical product in most countries, adverse event data received by the license holder (usually a pharmaceutical company) must be submitted to the local drug regulatory authority. The impact factor of Drug Safety journal is a measure reflecting the average number of citations to recent articles published in the journal. It is frequently used as a proxy for the relative importance of a journal within its field, with journals with higher impact factors deemed to be more important than those with lower ones.