Propecia is a drug for treating hair loss. Proscar is the same drug,
sued for a different purpose and sold at a higher dosage. To save
money, some people who are perscribed propecia will buy proscar and
break the pills in half, giving them something that is close to (but
still a little higher than) the recommended dosage. Is this as safe
and effective as taking propecia pills?

Hello again gremlin,

With respect to dosages, one of the articles I cited in response to
another of your questions gives the answer. The paper by Roberts and
colleagues, details of which I have pasted in again below found that a
1 mg dose (as found in Propecia) and a 5 mg dose (as found in Proscar)
were equally effective in the treatment of hair loss. The authors also
stated "No significant safety issues were identified in the trials". 
So half a Proscar tablet, which would give a dose of approx. 2.5 mg,
would fall within a dose range that is both safe and effective.

I also looked at the drug information on finasteride (ie Propecia and
Proscar) provided on Medline Plus at the National Library of Medicine
at
http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202649.html
One important piece of information from there is that if you do decide
to go this route, you must NEVER let a woman of childbearing age break
up the tablets for you "Women of childbearing potential should not use
or handle crushed finasteride tablets. Finasteride can cause birth
defects in male fetuses."

The article also has the following advice: "For individuals taking
this medicine for  hair growth: You may have to take this medicine for
at least 3 months to see an effect. The effect will last only as long
as the medicine continues to be used. The new hair will be lost within
1 year after finasteride is stopped." So if you do decide to use
Propecia, you will have to be prepared to continue with it on a
permanent basis or lose all the benefit. Proscar was approved by the
FDA for treatment of benign prostatic hyperplasia in 1992, but
Propecia was approved for treatment of male hair loss only in 1997. 
Therefore, little will be known so far about potential effects of
long-term treatment in humans.  This is something you might wish to
take into consideration when making your decision, depending on your
current age.

Of course, a further factor is that both Propecia and Proscar are
prescription-only drugs. You would have to find a doctor willing to
prescribe Proscar on the understanding that you will break up the
tablets and use half each time.

Article on dosage:
Roberts JL, Fiedler V, Imperato-McGinley J, Whiting D, Olsen E,
Shupack J, Stough D, DeVillez R, Rietschel R, Savin R, Bergfeld W,
Swinehart J, Funicella T, Hordinsky M, Lowe N, Katz I, Lucky A, Drake
L, Price VH, Weiss D, Whitmore E, Millikan L, Muller S, Gencheff C, et
al.
 Clinical dose ranging studies with finasteride, a type 2
5alpha-reductase inhibitor, in men with male pattern hair loss.
J Am Acad Dermatol. 1999 Oct;41(4):555-63. 
“Two separate clinical studies were conducted to establish the optimal
dose of finasteride in men with this condition.” (The numbers of
subjects are not reported) “Men from 18 to 36 years of age with
moderate vertex male pattern hair loss received finasteride 5, 1, 0.2,
or 0.01 mg/day or placebo…  Efficacy was demonstrated for all end
points for finasteride at doses of 0.2 mg/day or higher, with 1 and 5
mg demonstrating similar efficacy that was superior to lower doses.
Efficacy of the 0.01 mg dose was similar to placebo…  CONCLUSION:
Finasteride 1 mg/day is the optimal dose for the treatment of men with
male pattern hair loss”
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10495375&dopt=Abstract

Search strategy: The Medline article was retrieved for a previous
question. I was already aware of the drug information provided by
Medline Plus