Feuerstein 1986.

Study characteristics
Methods	Randomised, double‐blind, placebo‐controlled trial Study type: single‐centre study Location: Germany (Freiburg) Study design: parallel Randomisation: not described Allocation concealment: not described Blinding: blinding of participants and evaluation personnel Follow‐up period: until healing of the headache
Participants	Randomised: 16 (not described the number of participants initially allocated to each group) Excluded (post‐randomisation): 5 (not described how many from each group). Analysed: 11 (intervention group: 6; control group: 5) Gender (women): 6 (54%) Age (years); n (%): 4 (36.4%) 10 to 30 years old (intervention group 3; control group 1); 4 (36.4%) 31 to 50 years old (intervention group 1; control group 3); 3 (27.3%) > 50 years old (intervention group 2; control group 1) Baseline VAS score: not evaluated Inclusion criteria: patients with a diagnostic lumbar puncture performed, with no headache during the last week before the lumbar puncture and a severe headache Exclusion criteria: not described
Interventions	Intervention group: oral theophylline 281.7 mg tablets (verum Euphyllin retard tablets) 3 times a day Control group: oral placebo tablets 3 times a day Co‐interventions: analgesics and hypotonic saline solution as needed
Outcomes	Number of participants with a conservative supplementary therapeutic option offered Change in pain severity ("sum of pain") during the treatment period Number of any possible adverse events Missing data (withdrawals, drop‐outs and participants lost to follow‐up)
Notes	Post‐dural puncture headache (PDPH): Quote "Subjective severe headache occurring only after arising and ceasing within a few minutes after lying down.". (Page 217) Sum of pain: 1 = slight headache; 2 = intermediate headache and 3 = severe headache. 3 values per day Sample size calculation: not described
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information provided. Reported as randomised
Allocation concealment (selection bias)	Unclear risk	No information provided
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: "The placebo tablets, indistinguishable from the verum Euphyllin retard tablets (281.7 mg theophylline), were kindly provided by Byk Gulden Pharmazeutika, Konstanz, FRG." (Page 217) Quote: "Verum and placebo tablets were randomised so that neither the patient nor the examining medical staff knew the real content of the administered tablets." (Page 217)
Incomplete outcome data (attrition bias) All outcomes	High risk	5 of 16 participants randomised dropped out, with insufficient information provided Quote: "Five patients of 16 dropped out (transferal to other clinical departments, dismissal before the end of the study or insufficient compliance)." (Page 217)
Selective reporting (reporting bias)	High risk	The study report fails to include results for a key outcome (PDPH persistence of any severity at follow‐up) that would be expected to have been reported for such a study
Size of study	High risk	Total 11 (intervention group: 6; control group: 5)