I have not found the possible side effects of "sleepiness or lethargy" associated with Yaz or any other combination hormonal birth control pills. Have you spoken with your doctor about your symptoms? Click here for a list of common side effects from birth control pills from the ACOG.
Another list of side effects from MedlinePlus Drug Information says "extreme tiredness, weakness, or lack of energy" is a "serious side effect, and to call your doctor immediately". Your description of being tired/sleepy did not read as "extreme" from your post, but it would be a very good idea to check in with your doctor!
The FDA consumer information page on Yasmin (Yaz) provides some information on side effects specific to Yaz:
As far as I have researched, the side effects of Yaz are similar to those of other hormonal contraception combination pills, EXCEPT that Yaz has been shown to elevate potassium levels, which may cause irregular heartbeats in some women. I'm surprised your doctor had not heard of Yaz, and still prescribed it!
Yaz has an added ingredient that the others combination pills do not: drospirenone (synthetic progestin). According to Go Ask Alice,"
Drospirenone has antimineralocorticoid activity that influences the regulation of water retention and electrolyte balance in the body, as well as antiandrogenic (anti-male hormone) properties.
As a result of this particular progestin, common benefits of Yasmin include:
* less water retention
* less premenstrual weight gain
* fewer PMS and menstrual symptoms
* prevention of acne"
Yaz has been advertised to be used primarily for PMDD (a severe form of PMS), as well as acne. However, many other combination pills can help improve acne; you can ask your health care provider...some pills are more "advertised" for acne improvement, although many of the combination pills have the same ingredients (with more or less doses), and can help with acne.
Lastly, the Go Ask Alice site has a great post on how to talk with your doctor about your specific symptoms, so that you can be prescribed the hormonal contraception that is RIGHT for YOU, not just what is being most heavily advertised at the time. There are so many birth control pills out there...just take a look at the bottom of this page for a list of brand names (there are 42!!): http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a601050.html. And, I remember a few years ago Ortho-Tri Cyclen was "THE" birth control pill for acne, as it was most advertised at the time.. Each of these combination pills have different levels of estrogen and progestin, that it may take a couple of tries to find the one that works best for you. For example, if you are more concerned with acne, a pill with less estrogen and more progestin might work best. However, if you are more concerned with headaches, then the lower estrogen and lower progestin may be best.