If your blood pressure was initially in the 160s over 90s is 50 mg losartan a good dosage. Cardiologist put me on this.

BP treatment. Losartan 50 mg is a very good beginning dose. It likely will control your BP. The dose can be titrated upwards to 75 and 100 mg easily. Be sure you limit salt intake. Be sure you limit saturated fats. Be sure you work on your back pain so that you can limit NSAIDs, which can elevate BP a bit through salt retention.
Yes. After approximately 7-10 days on this dose, however, BP ought to be re-assessed and if BP still not optimal, uptitration to 100 mg ought to be considered.