# How to determine Single Therapeutic dosage?

I need some help in determining the single therapeutic dosage. Detailed responses will be greatly appreciated,

Case 1 (Only one active):

Product: Fluticasone Propionate Nasal Spray (700)
http://hitechpharm.com/products/product.aspx?title=Fluticasone%20Propionate%20Nasal%20Spray,%2050mcg&compareto=Flonase�&ndc=0700-16

Strength: 50 mcg

Information from product insert
http://hitechpharm.com/products/pi/pi_fluticasone.PDF

Dosage and Administration: The recommended starting dosage in adults is 2 sprays (50 mcg of fluticasone propionate each) in each nostril once daily (total daily dose, 200 mcg).

My Judgment:
Only one nostril will be counted, therefore SthD (Single Therapeutic Dosage) = 50 mcg = 0.005mg

Case 2 (Two actives in one Product):

Product:Dorzolamide Hydrochloride - Timolol Maleate Ophthalmic Solution (233)
http://hitechpharm.com/products/product.aspx?title=Dorzolamide%20HCl-Timolol%20Maleate%20Ophthalmic%20Solution&compareto=CoSopt�&ndc=0233-10

Strength: 22.3mg / 6.8mg per 1mL

Information from product insert
http://hitechpharm.com/products/pi/pi_dorzo_tim.pdf

Dosage and Administration: The dose is one drop of Dorzolamide Hydrochloride-Timolol Maleate Ophthalmic Solution in the affected eye(s) two times daily.

My Judgment:
Single Therapeutic Dosage = One drop
Volume of one drop = 0.04 mL
Now deteremine the amount of Active present in this volume
SthD = 0.04 (22.3 + 6.8) = 1.164mg

Am I correct to add the two actives?