i would say ethanol (grain alcohol) bro. Mine have stayed in solution for months now in ethanol. Just go to liquor store and pick up some everclear. This is what i would do if i were you:

What you would need:
1) letrozole powder (1,000mg)
2) (4) 100mL vials
3) A measuring cup that can hold atleast 500mL
4) 30cc syringe or bigger, to minimize time (i prefer 60cc terumo syringe, doesnt take as long)
5) accurate scale
6) 400mL Everclear

Say you wanted to make the solutions 2.5mg/mL. You have 1g (1000mg) of letrozole. so that equals 400mL final product. Remember, 1g usually displaces 1mL of liquid, so you will need 399mL of everclear.

First, measure out 399mL of everclear with the syringe, and put it in the measureing cup that holds 500mL or more (now you know why i said a 30cc syringe or bigger )
Second, measure out 1,000mg of letrozole powder, and add it to the everclear.
Third, stir it up a little bit and heat up.
Fourth, fill up the 100mL vials.

There is no need to filter it, as you will be using it orally, so sterility is not of concern. Now wasnt that easy?

on a side note, make sure after you heat up the everclear, you let it cool before trying to extract it and put in vials, dont wanna melt the tip of syringe. sounds like common sense, but i have done it more than once, you just get so anxious

This is what I was thinking.............I used bacardi 151 for some winny powder last year, that was some nasty tasting shit. How do you heat it, as well about how hot do you need it. I would be leary near a stove with everclear. I am guessing 1g of femera takes up 100cc of space? Thus giving 500ml of 2mg/ml?

no no, 1g letrozole displaces 1mL (1cc). but you are correct, at 2mg/mL you will have 500mL

so what you wanna do is get 499mL of evercler, instead of 399mL because your potency will be different than the 2.5mg/mL. Also, to heat it, you can actually put in microwave. Your right, open-flame stove could be dangerous (microwaves wont harm solution, dont worry) just heat until powder is no longer visible and you have a clear solution. If i remember correctly, this will happen before it reaches a boil