Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
Level II | Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
Level III | Other | Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[49] Amitriptyline, oral: Descombes S, Brefel-Courbon C, Thalamas C, Albucher JF, Rascol O, Montastruc JL, Senard JM. Amitriptyline treatment in chronic drug-induced headache: a double-blind comparative pilot study. Headache. 2001 Feb;41(2):178-82. https://www.ncbi.nlm.nih.gov/pubmed/11251703