[india-drug] RE: Omeprazole (3)

["Nusrat Shafiq" <nusrat_shafiq@hotmail.com>]

Omeprazole (3)
******** 

Dear Pranav,

You have already received the replies to the first three questions 
correctly.

I would just like to add on to the reply for the last question.
All PPI are weak bases and are acid labile. Several enteric coated 
formulations are available to circumvent this problem. Enteric coating, 
however, leads to a longer Tmax (nearly 5hrs). Buffering with sodium 
bicarbonate not only prevents its degradation, it also leads to early 
release of omeprazole from its preparations reducing the Tmax.

An immediate release preparation has been approved by FDA for controlling 
upper GI bleeding in critically ill patients based on a result of a 
randomized controlled trial. Interestingly, however, in this trial, the 
novel preparation was compared to cimetidine and not i.v omeprazole. The 
difference in the clinical end point of breakthrough bleeding was 6.8% and 
4.5% respectively for cimetidine and the alkali buffered preparation. though the results were statistically significant (which with large sample size minutest diff would be), it has to be interpreted cautiously.
The preparation is also approved for the other usual indications of PPI

Again, because of NaHC03, it has to be given cautiously to patients with 
CHF, with metabolic alkalosis, hypocalcemia, Bartter's syndrome

P.S: The patent life of most of the PPI is ending and companies are coming 
up with this 'novel formulation trick' to extend the life of patent. 
Recently Astra Zeneca's Nexium  which is nothing but a me-too of Prilosec 
got approval. It offers no clinically significant advantage over Prilosec 
and apparently it was deliberately launched just when Prilosec's patent life 
was about to expire.

Best Regards

Dr Nusrat S.Khan
M.D(Pharmacology), D.M(Clinical Pharmacology)
PGIMER, Chandigarh
"Nusrat Shafiq" <nusrat_shafiq@hotmail.com>