A Phase IV trial is also known as postmarketing surveillance trial, or informally as a confirmatory trial . Phase IV trials involve the safety surveillance ( pharmacovigilance ) and ongoing technical support of a drug after it receives permission to be sold (. after approval under the FDA Accelerated Approval Program ).  Phase IV studies may be required by regulatory authorities or may be undertaken by the sponsoring company for competitive (finding a new market for the drug) or other reasons (for example, the drug may not have been tested for interactions with other drugs, or on certain population groups such as pregnant women, who are unlikely to subject themselves to trials).   The safety surveillance is designed to detect any rare or long-term adverse effects over a much larger patient population and longer time period than was possible during the Phase I-III clinical trials.   Harmful effects discovered by Phase IV trials may result in a drug being no longer sold, or restricted to certain uses; recent examples involve cerivastatin (brand names Baycol and Lipobay), troglitazone (Rezulin) and rofecoxib (Vioxx). The minimum time period mandatory for Phase IV clinical trials is 2 years. [ citation needed ]
Five randomised trials met our inclusion criteria (n = 302). Three studies objectively measured infant breastfeeding using standardised assessment tools. Pooled analysis of two studies (n = 155) showed no change on a 10-point feeding scale following frenotomy ( mean difference ( MD ) -, 95% confidence interval ( CI ) - to units on a 10-point feeding scale). A third study (n = 58) showed objective improvement on a 12-point feeding scale ( MD , 95% CI to units of a 12-point feeding scale). Four studies objectively assessed maternal pain. Pooled analysis of three studies (n = 212) based on a 10-point pain scale showed a reduction in maternal pain scores following frenotomy ( MD -, 95% CI - to - units on a 10-point pain scale). A fourth study (n = 58) also showed a reduction in pain scores on a 50-point pain scale ( MD -, 95% CI - to - units on a 50-point pain scale). All studies reported no adverse effects following frenotomy. These studies had serious methodological shortcomings. They included small sample sizes, and only two studies blinded both mothers and assessors; one did not attempt blinding for mothers nor for assessors. All studies offered frenotomy to controls, and most controls underwent the procedure, suggesting lack of equipoise. No study was able to report whether frenotomy led to long-term successful breastfeeding.