When a drug patent expires, the FDA may grant a six-month exclusivity period to one company to produce the generic version. During this time it is a "single-source" generic drug, produced by only one manufacturer and priced higher than multi-source generics. After the exclusivity period expires, other manufacturers can produce generic versions, and the drug becomes "multi-source." Examples given include paracetamol, which is now available generically from many sources due to expired patents.

2. • When a company patents a drug, that
company is the only manufacturer of the
drug.
• When a patent expires for a brand drug, the
FDA sometimes grants a period of exclusivity
(typically lasting six months) to one company
to make the generic form of the drug.
• The company may be the same maker as the
brand drug or an entirely different company.

3. • During this time, there is a “single
source” for the generic drug and no other
company can produce the generic until
the exclusivity period expires.
• A single-source generic drug is more
expensive than other generics because
the drug is made by only one
pharmaceutical company.

4. • A multisource drug product is a drug
product that contains the same active
drug substance in the same dosage form
and is marketed by more than one
pharmaceutical manufacturer.

5. • The day the patent expires and multiple
manufacterers are allowed to produce therapuetical
equiviquent, drug becomes multi source as it is
produced by more than one source.
• This applies to both brand and generic drugs. When
generics are released to marketplace, the first
generic is considered to "hold original patent" and
therefore is allowed to price as a brand.
• All other generics thereafter for that drug are called
"non-innovators" and price as true generics.

6. • The compound patent on abacavir expired in
2010 in all jurisdictions
• However, other patents on forms and
formulations of abacavir that may affct the
market for abacavir and abacavir-containing
formulations.
• A patent on the hemisulfate salt is expected to
expire in 2018.
• Until then, it is found from a single source:
(VIIV HEALTHCARE)

7. • There are many examples of multiple source
generic drugs!
• For example; the most available drug:
paracetamol.
• The U.S. patent on paracetamol has expired
long ago.
• Generic paracetamol are widely available
under the Drug Price Competition and Patent
Term Restoration Act of 1984 in U.S.A. from
many sources.

8. • FDA has evaluated for therapeutic equivalence only
multisource prescription drug products approved
under Section 505 of the Act.
• For such products, a therapeutic equivalence code
is included and, in addition, product information is
highlighted in bold face and underlined.
• Those products with approved applications that are
single-source are also included on the List, but no
therapeutic equivalence code is included with such
products.

9. • Any drug product in the List repackaged and/or
distributed by other than the application holder is
considered to be therapeutically equivalent to the
application holder's drug product even if the
application holder's drug product is single source or
coded as non-equivalent (e.g., BN).
• Also, although not identified in the List, distributors
or repackagers of an application holder's drug
product are considered to have the same code as
the application holder.

10. • Orange Book Preface, FDA:
http://www.fda.gov/Drugs/DevelopmentApprovalPr
ocess/ucm079068.htm
• https://hmsa.com/help-center/single-source-
generic-drugs/
• “Patents and licences on antiretrovirals: A
snapshot”; UNITAID, WHO, Volume: April 2014
• http://www.bimsifram.fr/paracetamol/history_para
cetamol.htm