Here is the design of a clinical trial:

Official Title: Effect of the Oral Route of Magnesium on Pre and Post-mastectomy on the Post-surgery Pain

Included conditions:
- Neuropathic Pain Induced by Mastectomy

Study Armgroups:
- {'label': 'magnesium', 'type': 'EXPERIMENTAL', 'interventionNames': ['Drug: Magnesium: Magnésium UPSA Action Continue®']}
- {'label': 'placebo', 'type': 'PLACEBO_COMPARATOR', 'interventionNames': ['Drug: Placebo: Lactose']}

Interventions:
- {'type': 'DRUG', 'name': 'Magnesium: Magnésium UPSA Action Continue®', 'description': 'This clinical trial compares magnesium and placebo for the prevention of neuropathic pain induced by mastectomy assessed with a (0-10) numerical pain rating scale', 'armGroupLabels': ['magnesium']}
- {'type': 'DRUG', 'name': 'Placebo: Lactose', 'description': 'This clinical trial compares magnesium and placebo for the prevention of neuropathic pain induced by mastectomy assessed with a (0-10) numerical pain rating scale', 'armGroupLabels': ['placebo']}

Primary Outcomes:
- {'measure': 'Measure of average pain intensity by a numerical rating scale', 'description': 'Measure of average pain intensity by a numerical rating scale assessed 5 days before the visit at 1 month post-mastectomy in magnesium and placebo groups.', 'timeFrame': '5 days before the visit at 1 month post-mastectomy'}

Please estimate the sample size based on the assumption: 
Significance level (α) is 0.05 (two-sided type I error) and power (β) is 0.10.
Sample size calculation
        Sample size estimation has been performed using Stata software V.13 (StataCorp) with command sampsi based on usual sample size estimation.49 Considering the literature, the prevalence of postmastectomy pain is 20%.50 51 However, these data may vary depending on demographic, psychological and medical/surgical factors52 and will be taken into consideration in this study. The number of subjects required is 100 patients with breast cancer undergoing total mastectomy (50 in each group). The minimum Î´ difference in numerical pain scale between magnesium and placebo groups at M1 is estimated at 1.0 and Ï standard deviation at 1.5 with Î±=0.05âtwo-sided type I error and Î²=0.10.