Schmidt 1979.

Methods	1) Randomisation: not reported. 2) Allocation concealment: the numbers 1 to 12 were randomly assigned to packages of six bottles containing 180 capsules of 200 mg of either theophylline or placebo. Six of these packages contained three bottles labeled months 4,5, and 6. Six packages contained drug and placebo in reverse manner. 3) Masking: Double blind. Placebo tablets had the same appearance as theophylline. 4) Withdraw/Drop‐out: one dropped out after month 4 treatment. 3 patients had to be crossed over because of the treament efficacy, one after several days, one after 2 weeks, and the third after months. 5) Duration intervention: 3 months x 2 6) Design: Cross‐over groups. 7) Jadad quality score: 5 8) Location: Pennsylvania, USA
Participants	1) Inclusion outpatients criteria:COPD, without improve 15% response to inhaled isoproterenol. 2) Definition of COPD: FEV1 less than 70% of predicted. 3)Type of exercise test: none. 4) Definition of stable COPD: not described. 5) Age: not described (range 30 to 70) 6) FEV1: Mean = 1.05, SD not described. 7) Number of patients:12. Drop‐out: 1 (11 patients completed the study). 8) Baseline therapy: not reported. 9) Exclusion criteria: not reported.
Interventions	THEOPHYLLINE GROUP (n = 11, completed the study) 1) Drug: Elixophyllin 200mg capsules. 2) Short or long action: Short‐action 3) Dose: 800 mg theophylline per day total (dosing was 200mg qid). 4) Washout: not reported 5) Theophylline blood level: not measured. PLACEBO GROUP (n = 11, completed the study)
Outcomes	1) Pulmonary function tests (FVC (L), FVC (% pred), FEV1 (L), FEV1 (% pred), MMFER (L/min). Maximal mid flow expiratory rate. 2) Patient questionnaire pulmonary status 3) Symptom: subjective 4) Heart rate
Notes	1) Intention‐to‐treat analyses: no. 2) Sample size and statistical power: not reported. 3) Representativity: not described.
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Low risk	A ‐ Adequate