Here is the design of a clinical trial:

Official Title: Efficacy of Metamizole Versus Ibuprofen and a Short Educational Intervention Versus Standard Care in Acute and Subacute Low Back Pain: A Randomized, Factorial Trial

Included conditions:
- Low Back Pain

Study Armgroups:
- {'label': 'metamizole + educational intervention', 'type': 'ACTIVE_COMPARATOR', 'description': '(A) Metamizole (Novalgin® Oblong tablets 0,5 g) orally three times daily 2 capsules for 4 days followed by an as needed regimen (days 4 - 42). The treatment duration will depend on the duration of pain. Patients are considered to be recovered when their pain is below 2 (NRS 0-10) on 2 consecutive days after they stopped the pain medication (end of treatment).\n\n(B) Educational short intervention: patients receive two leaflets with information non-specific LBP and exercises to alleviate LBP. Further, patients receive a 10-minute standardized telephone intervention during the first 4 treatment days.', 'interventionNames': ['Drug: Metamizole Sodium', 'Behavioral: Patient education']}
- {'label': 'metamizole + standard care', 'type': 'ACTIVE_COMPARATOR', 'description': '(A) Metamizole (Novalgin® Oblong tablets 0,5 g) orally three times daily 2 capsules for 4 days followed by an as needed regimen (days 4 - 42). The treatment duration will depend on the duration of pain. Patients are considered to be recovered when their pain is below 2 (NRS 0-10) on 2 consecutive days after they stopped the pain medication (end of treatment).\n\n(B) Standard care will be prescribed by the GP.', 'interventionNames': ['Drug: Metamizole Sodium']}
- {'label': 'ibuprofen + educational intervention', 'type': 'ACTIVE_COMPARATOR', 'description': '(A) Ibuprofen (Ibufen-L® tablets 500 mg) orally three times daily 2 capsules for 4 days followed by an as needed regimen (days 4 - 42). The treatment duration will depend on the duration of pain. Patients are considered to be recovered when their pain is below 2 (NRS 0-10) on 2 consecutive days after they stopped the pain medication (end of treatment).\n\n(B) Educational short intervention: patients receive two leaflets with information non-specific LBP and exercises to alleviate LBP. Further, patients receive a 10-minute standardized telephone intervention during the first 4 treatment days.', 'interventionNames': ['Drug: Ibuprofen 600 mg', 'Behavioral: Patient education']}
- {'label': 'ibuprofen + standard care', 'type': 'ACTIVE_COMPARATOR', 'description': '(A) Ibuprofen (Ibufen-L® tablets 500 mg) orally three times daily 2 capsules for 4 days followed by an as needed regimen (days 4 - 42). The treatment duration will depend on the duration of pain. Patients are considered to be recovered when their pain is below 2 (NRS 0-10) on 2 consecutive days after they stopped the pain medication (end of treatment).\n\n(B) Standard care will be prescribed by the GP.', 'interventionNames': ['Drug: Ibuprofen 600 mg']}

Interventions:
- {'type': 'DRUG', 'name': 'Metamizole Sodium', 'description': 'Novalgin® Oblong tablets 0,5 g 2-2-2', 'armGroupLabels': ['metamizole + educational intervention', 'metamizole + standard care'], 'otherNames': ['Metamizole']}
- {'type': 'DRUG', 'name': 'Ibuprofen 600 mg', 'description': 'Ibufen-L® tablets 500 mg 2-2-2', 'armGroupLabels': ['ibuprofen + educational intervention', 'ibuprofen + standard care'], 'otherNames': ['Ibuprofen']}
- {'type': 'BEHAVIORAL', 'name': 'Patient education', 'description': 'Leaflet and phone call', 'armGroupLabels': ['ibuprofen + educational intervention', 'metamizole + educational intervention'], 'otherNames': ['Education']}

Primary Outcomes:
- {'measure': 'Pain improvement', 'description': 'Change in pain on the numeric rating scale (NRS, range 0 (no pain) -10 (worst possible pain) points)', 'timeFrame': 'Baseline to 14 days follow-up'}
- {'measure': 'Disability', 'description': 'Change in the Core Outcome Measures Index (COMI) sum-score (range 0-10). COMI sum score (0-10 points) is calculated by averaging the five domain scores (each on a 0-10 scale) for pain, back-related function, symptom-specific well-being, general quality of life and disability. Higher values represent a better or worse outcome.', 'timeFrame': 'Baseline to 42 days follow-up'}

Please estimate the sample size based on the assumption: 
The type-I error rate is adjusted to 0.025 for each test to maintain an overall type-I error rate of 0.05. The power is set at 90%, and a drop-out rate of 10% is accounted for. The standard deviation (SD) for the NRS is assumed to be 1.6, and for the COMI, it is assumed to be 2.2 points.
Estimated sample size and power
        Both interventions are considered for determining the sample size for this factorial trial.34 We expect the two primary hypotheses to be independent of each other and do not expect an interaction between both interventions. Therefore, we powered each hypothesis individually, but accounted for multiple testing by adjusting the type-I error rate by setting the alpha level to 0.025 in each test to keep the overall type-I error rate at 0.05. Thus, we aimed to include 120 patients to account for a drop-out of 10% which will allow to proof non-inferiority of the metamizole treatment at a one-sided alpha-level of 2.5% with a power of 90%.
        The sample size calculation for the comparison of metamizole versus ibuprofen was based on a difference in the change of pain score in the Numeric Rating Scale (NRS; range 0â10, higher score indicates more pain). We considered a change of â¥2 points between the two groups as clinically relevant and a change of â¤1 point as negligible.35 36 Therefore, we set the non-inferiority margin to â1 score point. Based on a two-sample means test and an SD of 1.6,35 we will need 108 patients (54 per group) to proof non-inferiority of the metamizole treatment at a one-sided alpha-level of 2.5% with a power of 90%.
        The sample size for the primary outcome comparison short intervention versus usual care (superiority) is based on a change in Core Outcome Measures Index (COMI; range 0â10, higher score indicates higher level of complaint, see primary outcomes) from baseline to week 6. We hypothesise that there is a difference between the two intervention groups regarding COMI. Mannion et al37 reported a minimal clinically important difference (MCID) for improvement in the COMI of 2.2 points and SD for changes in COMI ranging from 1.7 to 2.5 points. We see a difference of 2.2 points between the two groups as clinically relevant and assume a SD of 2.2 points. Based on a two-sample means test, we will need 54 patients (27 per group) to detect a difference in the change of the COMI at a two-sided alpha-level of 2.5% with a power of 90%.