What is the equivalent dose for losartan 50 daily in diltiazem pls?

No equivalence: Diltiazem, a calcium channel blocker, cannot be substituted for losartan, and angiotensin receptor blocker. Both may be used to lower bp, but there is no simple way to figure if the patient is a good candidate for a switch or what kind of dose should be used. Depends on too many variables.

Equal dose?: You are comparing apples, losartan (L), with oragnes, Diltiazem (D). Both lower blood pressure and so by different means. Instead of focusing on the dose, in mg, one should focus on how well one's blood pressure is controlled and the any adverse side effects. Speak to your physician (P), as your P knows the you best of all.