The aim of this study is to test if alkali treatment will preserve kidney graft function and diminish the progression of chronic kidney disease in renal transplant patients. Additionally the underlying mechanisms of nephrotoxicity of metabolic acidosis will be investigated in this cohort.

This study is a multi-center, prospective, randomized, single-blind (patient), placebo-controlled interventional trial to test the superiority of alkali treatment in comparison to placebo on preservation of kidney function in 300 kidney transplant recipients. The duration of the study will be 2 years for the individual participant. The patients will be randomized into 2 arms: intervention arm (sodium hydrogen carbonate, product: Nephrotrans®) and placebo arm (placebo comparator).

Several studies in CKD (chronic kidney disease) patients have shown that alkali therapy slows progression of CKD.

Inclusion Criteria:

• Informed consent as documented by signature
• age ≥ 18 years and able to give informed consent
• ≥ 12 months after renal transplantation
• stable clinical condition
• stable graft function over the last 3 months (creatinine changes ± 15%)
• eGFR between 15-89 ml/min/1.73 m2
• serum bicarbonate ≤ 22 mmol/l within the last 6 months

Exclusion Criteria:

• uncontrolled hypertension or use of > 4 antihypertensive agents
• uncontrolled heart failure
• serum potassium < 3.0 mmol/l
• serum sodium > 150 mmol/l
• use of alkali in the preceding 4 weeks
• use of mineralocorticoid antagonists, topiramate, carbo anhydrase inhibitors or any drugs with similar effects
• history of noncompliance with clinic visits
• hereditary fructose intolerance
• known hypersensitivity or allergy to the drug used in this study or to peanut, sorbitol, and soy
• pregnancy or breastfeeding
• intention to become pregnant during the course of the study
• lack of safe contraception, defined as: Female participants of childbearing potential, not using and not willing to continue using a medically reliable method of contraception for the entire study duration, such as oral, injectable, or implantable contraceptives, or intrauterine contraceptive devices, or who are not using any other method considered sufficiently reliable by the investigator in individual cases.
• please note that female participants who are surgically sterilised / hysterectomised or post-menopausal for longer than 2 years are not considered as being of child bearing potential.
• suspected drug or alcohol abuse
• inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant
• enrolment of the investigator, his/her family members, employees and other dependent persons