Tag Archives: auxiliary substances

Stability Studies of Ampicillin Trihydrate in Suspensions and Acidic Aqueous Solutions

Rad I.1, Croitoru M. D.2, Pálffy Ágnes2, Gyéresi Á.3

1 “Dimitrie Cantemir” College, Tg. Mures
2 Public Health Centre, Tg. Mures
3 University of Medicine and Pharmacy of Tîrgu Mureș, Faculty of Pharmacy

Background: Ampicillin in trihydrate form is a b-lactamine antibiotic frequently used in therapy as suspensions and capsules. Because of the low stability only dry suspensions are sold, and also the low stability in acidic environment is source of unwanted side effects and bioavailability variations.
Aim: Our goal was to stabilize ampicillin so that a better stability can be obtained both in water suspensions and acidic solutions. This way misuse due to faulty preparation, side effects and bioavailability problems can be avoided.
Methods: In order to assess the changes in the ampicillin concentration high performance liquid chromatography (HPLC) and thin layer chromatography (TLC) methods have been used.
Results: None of the tried excipients improved stability of ampicillin suspensions. In contrast cyclodextrins and magnesium salts of glutamic and aspartic acid greatly improved the stability of ampicillin acidic solutions. In high amounts cyclodextrins also change the decomposition kinetic of ampicillin, which is usually a first order kinetic process.
Conclusions: Cyclodextrins and magnesium salts of glutamic and aspartic acid have the potential to be used in ampicillin containing formulations in order to increase its stability, bioavailability and to reduce adverse effects.

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Improvements of Amoxicillin Stability in Acidic Environment

Rad I.1, Croitoru M.D.2, Gyéresi Á.2

1 “Dimitrie Cantemir” College, Tg. Mures
2 Faculty of Pharmacy, University of Medicine and Pharmacy Tg. Mures

Background: Helicobacter pylori is a gram negative bacteria responsible for a series of gastrointestinal diseases: gastric and gastroduodenal ulcers. Usually used in combinations with other drugs, amoxicillin is effective against this germ. Amoxicillin has better stability than other penicillins in solutions with pH between 4 and 7, but stability is decreased at low pH values (gastric acidity).
Aim: Our goal was to improve amoxicillin’s stability by using auxiliary substances such b-cyclodextrin (b-CD), 2-hydroxypropil-bcyclodextrin (2-HP-b-CD), magnesium glutamate and magnesium aspartate.
Methods: Influence of these excipients on amoxicillin stability was assessed at pH value of 1.2 and also in weakly alkaline environment. High pressure liquid chromatography and thin layer chromatography were used to quantitate these influences.
Results: All the studied excipients improved the stability of amoxicillin, best results being recorded when amoxicillin was associated with cyclodextrins in a mole ratio of 1:5.
Conclusions: Poor stability of amoxicillin in acidic environments can be overcome by using cyclodextrins and magnesium salts of glutamic and aspartic acids.

Keywords: , , ,
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