Osteoporosis is a common disease defined as a decrease in bone mass and strength which increases risk of fragility fractures. This disorder may affecting health in many adults which causing disability, morbidity, and mortality. Current first-line medical therapy is bisphosphonates which alendronate is one of the most widely used. However, expenditure on medicines is one of the major problem of inadequate access to treatment.

The investigators hypothesized that generic alendronate will have the same clinical efficacy as the brand formulation. Therefore, the result of this study is extremely crucial. If adequate efficacy of generic alendronate could be established and if it affords the same safety profile as those of brand alendronate, the use of generic alendronate could then be recommended.

Osteoporosis is a common disease which estimated that over 200 million people worldwide are suffered. The prevalence is continuing to escalate with the increasingly elderly population. The risk of fragility fractures in elder over age 50 is approximately 50% in women and 20% in men.

Current first-line medical therapy is bisphosphonates which alendronate is one of the most widely used. However, expenditure on medicines is one of the major problem of inadequate access to treatment. Generally, insurances and health care providers prefer physicians to prescribe generic instead of brand drug, due to its lower costs. However, clinical information on bone mineral density (BMD), fracture reduction and side effects with new generic alendronate is limited.

The objective of this study is to evaluate the efficacy and safety of a new generic alendronate (Bonmax®) comparing to brand alendronate (Fosamax®). The efficacy of generic alendronate will be determined by measuring the percent changes of bone mineral densities at lumbar spine and total hip after 1 year of treatment and then comparing to those changes in the brand alendronate group.

Inclusion Criteria: patients who are postmenopausal women or men who aged older than 50 years and meet the indications for osteoporosis treatment according to the Thai Osteoporosis Foundation's 2010 treatment guidelines.

• History of spinal or hip fractures with low energy trauma.
• BMD by Dual energy X-ray absorptiometry (DXA) scan with T-score ≤ -2.5 at the femoral neck, total hip, or L1-L4 spine.
• BMD by DXA scan with T-score between -1 and -2.5 at the femoral neck, total hip, or L1-L4 spine and a 10-year hip fracture probability ≥ 3% or a 10-year major osteoporosis-related fracture probability ≥ 20% based on Fracture risk assessment tool (FRAX)

Exclusion Criteria:

• Patients who have contraindications to use bisphosphonates e.g. gastroesophageal reflux disease or drug allergy to bisphosphonates
• Patients with an abnormality of serum calcium levels (more than 10.2 mg/dl or less than 8.7 mg/dl)
• Patients with estimated glomerular filtration rate less than 30 mL/min/1.73 m2
• Patients with metabolic bone diseases such as Paget's disease, hyperparathyroidism, etc.
• Patients who were received anti-osteoporotic drugs during the past 1 year.
• Patients who currently taking steroids, hormone replacement therapy, or selective estrogen receptor modulators (SERMs) within 1 year.

small sample sizes and only one generic brand of bisphosphonate was used.