Inclusion Criteria:
The cohort will include older adult men aged 66 years or older with advanced CKD (an eGFR \<45 mL/min per 1.73 m² but not receiving dialysis or having a history of kidney transplantation) who have filled a new oral prescription for tamsulosin at an outpatient pharmacy under the Ontario Drug Benefit (ODB) program from January 1, 2008, to December 01, 2024. The age criterion is set to guarantee that individuals in this population had at least one year of prior prescription drug coverage. The date when the prescription was filled will serve as the patient's entry or index date for the cohort, with each patient entering the cohort only once.
Exclusion Criteria:
1. Data cleaning exclusions (e.g., individuals with missing or invalid age or administrative database number, OHIP ineligible on index date, death on or before the index date, non-Ontario residents). The investigators anticipate that very few records will be excluded due to data cleaning.
2. The investigators will exclude patients receiving tamsulosin doses other than 0.4mg/day or 0.8mg/day.
3. To ensure that patients are new tamsulosin users, the investigators will exclude those with any evidence of tamsulosin use in the 180 days before the index date.
4. Patients with more than one study drug prescription on the index date will be excluded, as this complicates the ability to ascertain the prescribed dose accurately.
5. The investigators will exclude patients with a prescription of Alpha1 blocker (alfuzosin, doxazosin, prazosin, silodosin, terazosin), 5 Alpha Reductase inhibitor (dutasteride, finasteride, dutasteride \& tamsulosin), and non-oral study drugs in the previous 180 days, including the index date.
6. Individuals with end-stage renal disease, chronic dialysis, or a kidney transplant prior to the index date.
7. Evidence with hospital discharge or emergency department visit in the two days prior to or on the index date to ensure a new outpatient prescription.
8. Patients with no outpatient serum creatinine measurement 0- 365 days before the index date will be excluded.
9. Patients with unstable baseline kidney function (If the most recent serum creatinine test before the index date was an inpatient test \[ER or hospitalization\] \<refer to this as test date 1\>, and there is not at least one 'outpatient' serum creatinine in the year before test date 1) (If the most recent prior serum creatinine test before the index date was an inpatient test \[ER or hospitalization\] \<refer to this as tests test date 1\>, and while there is at least 'outpatient' serum creatinine test in the year before \<test date 1\>, the most recent outpatient test before \<test date 1\> differs by an eGFR 10 mL/min/1.73 m2 or more from the value on \<test date 1\>) will be excluded. In Ontario, it has been shown that outpatient serum creatinine measurements in the province, conducted on a single occasion, indicate stable values.
10. If more than one eligible prescription is available, restrict it to the first. The date of this prescription will be the index date
