Pharmacokinetic patent...!!! (In Detail)

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Adams Respiratory Therapeutics  versus Perrigo - construction of the pharmacokinetic  claim in terms of Cmax

  • A company named Adams Respiratory Therapeutics  holds a patent number (5, 372, 252,) and this patent  covers an ER formulation that contains guaifenesin (it is an expectorant which is used to thin, loosen, and help to expel  the mucus which  causes congestion).
  • Perrigo tried for the FDA approval for a generic of Adams' product, Mucinex(r).
  • After construing the claims, the district court granted judgment of noninfringement.  Then Adams appealed that decision given by  the court. 
  • The claim terms in the conflict is  related to the pharmacokinetic parameters. 
  • These pharmacokinetic parameters evaluate the extent of absorption and bioavailability of the API (active pharmaceutical ingredient)). 
  • The major term of the claim is regarding the Cmax of the API.


  • The main conflict between the two companies  was over the meaning of the term "equivalent" in the context of "providing a Cmax in a human subject that is equivalent to the Cmax obtained when the first of three doses of a standard immediate release formulation having one third the amount of guaifenesin is dosed."  
  • An FDA approval,requires  a formulation that is bioequivalent if, among other things, its Cmax is within 80% to 125% range  with which it is being compared at a 90% confidence interval.The district court agreed with Perrigo's arguement that "equivalent" should be construed to mean the term  equivalent under the FDA bioequivalence guidelines.
  • Adams challenged for a 90% confidence interval arguing that it makes sense after FDA approval but not with acquiring infringement.
  • The Federal Circuit agreed with Adams appeal.  In doing that so, it rejected the following Perrigo's argument that the inventors had expressly defined  the term"equivalent" as to FDA's bioequivalence guidelines.




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Eswar GsnkRao's picture

Informative blog and nice case study.

Keep on giving such real stories.

Good day


ESWAR :-) 

Sandhya Sravya malla's picture

Thank you so much




Dr.S.Gunasakaran's picture

Nice one. Patent challenges are becoming common scenario in the US Generic market.

Dr.S.Gunasakaran,MBBS,MD. Head - Clinical Research & Medical Affairs

swapnamarabhoina's picture

Very useful information especially for students who have ideas to work in an industry..!!

Good Blog


swapna marabhoina

Reshma Tangirala's picture

I learnt a lot about patents,but never heard of pharmacokinetic patent..Nice and important info





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