Dehydration of Crystalline Theophylline Monohydrate and Ampicillin Trihydrate

Shefter, Eli; Fung, Ho‐Leung; Mok, Olivia

doi:10.1002/jps.2600620518

Cited by 54 publications

(29 citation statements)

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“…The existence of regions with different dehydration-rates is a strong evidence of a multi-step dehydration process. Although the studies of Shefter et al 53 and Agbada and York 51 seem to indicate that dehydration of TPh occur in a one-step process, several other studies suggest that the process may present two steps, depending on the experimental conditions (namely, dehydration temperature). 36,37,52,54,55 In fact, the definition of the experimental conditions is critical in these studies.…”

Section: Dehydration Process Of Tphmentioning

confidence: 96%

“…TPh and TPh ! TPa transformations, and both processes have been studied for the bulk powder 38,[44][45][46][47][48][49][50][51][52][53][54][55][56] and for tablets. [57][58][59][60] The effects of different excipients on these hydration and dehydration processes have also been evaluated by different authors.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, the results of Otsuka et al 57,58 suggest that the hydration rate of TPa tablets decreases with increase of tableting pressure and of porosity, while contradictory results were obtained by Suihko et al 38 In what concerns the dehydration process of TPh, different kinetic mechanisms have been suggested. 44,[51][52][53]55,57,58 Moreover, very different values were also determined for the activation energy (E a ) of the process. 44,[51][52][53]55,57,58 In an attempt to explain these discrepancies, Agbada and York 51 even suggested that both process mechanism and activation energy are techniquedependent.…”

Section: Introductionmentioning

confidence: 99%

“…44,[51][52][53]55,57,58 Moreover, very different values were also determined for the activation energy (E a ) of the process. 44,[51][52][53]55,57,58 In an attempt to explain these discrepancies, Agbada and York 51 even suggested that both process mechanism and activation energy are techniquedependent. Of course, it is more likely that the Attending to the factors described above, it is particularly important to study the two processes using the same experimental methodology (milling degree, temperature, humidity, and analysis technique).…”

Section: Introductionmentioning

confidence: 99%

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Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Amado

Nolasco

Ribeiro‐Claro

2007

Journal of Pharmaceutical Sciences

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Theophylline is known to undergo vapor phase induced hydrate-anhydrate pseudopolymorphic transformations, which can affect its bioavailability. In this work, the kinetics of the pseudopolymorphic transitions of theophylline crystals in different storage conditions is studied using a vibrational spectroscopic technique. While the hydration is a single-step process with a half-life time of ca. 5 h, the dehydration occurs through a two-step mechanism. In addition, the phase stability of hydrate-anhydrate systems in different relative humidity (RH) conditions was probed. The critical RH for anhydrous teophylline was found to be at ca. 79%, while the critical RH for dehydration is ca. 30%. ß

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Section: Dehydration Process Of Tphmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Amado

Nolasco

Ribeiro‐Claro

2007

Journal of Pharmaceutical Sciences

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“…No other evidence for the monohydrate formulation was offered. Subsequent detailed studies both in these laboratories (Austin, Marshall & Smith, 1965) and elsewhere (Poole & Bahai, 1968;Kamiya & Nishikawa, 1970;Shefter, Fung & Mok, 1973) showed that ampicillin actually crystallises from water at temperatures below 315 K as needles of the trihydrate, which when dried in vacuo gradually lose water to give a hygroscopic product. Ampicillin trihydrate has been subjected to full X-ray crystallographic analysis (James, Hall & Hodgkin, 1968), as has the anhydrate which crystallises from water above 315 K (Boles & Girven, 1976).…”

Section: Introductionmentioning

confidence: 99%

Can metastable crystal forms `disappear'?

Jacewicz¹,

Nayler²

1979

J Appl Cryst

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SHORT COMMUNICATIONSBabinet's principle of optical reversibility. From this principle the scattering depends only on the presence of discontinuities, in this case of electron density, irrespective of the sign (high or low) of the densities. In polycrystalline solids it is not possible, therefore, to decide whether the parameters calculated must be attributed to the solid particles or to the interstices between them. Guinier & Fournet (1955) have pointed this out already for X-ray scattering at small angles. As a result, the question remained undecided for a long time, whether in cellulose the microcrystallites (so called 'elementary fibrils') or the voids (or other materials between them) are associated with the parameters calculated. In the case of cellulose this question has been raised by Statton (1956) and Caulfield (1971). Statton maintained that the voids (interstices) rather than the microcrystallites are the units in question and Caulfield even added that, because of the inherent ambiguity of interpretation, the method of scattering at small angles may have rather 'confused than solved the issue of the size of the elementary particles in cellulose'.One way to solve this problem is by impregnating the intercrystalline regions with substances of another (higher) electron density and studying the effect on the scattering. The author applied intercrystalline swelling and by studying the effects on the radial distribution of the scattering elements arrived at the conclusion that the microcrystallites are the units to which the parameters calculated belong. This method can only be applied, however, when interparticle interference occurs in the unswollen sample.The observations with high-resolution microscopy mentioned above directly confirm the conclusions from the swelling experiments and radial distribution, that the parameters calculated must be attributed to the microcrystallites and that the voids have other diameters. From the above analysis it appears that the assumptions made concerning the uniformity and orientation of the particles and the particle sizes determined with the X-ray scattering method are fully confirmed by electron microscopy, and that the latter complements the X-ray method in the identification of the scattering entities in the case of a polycrystalline solid. Cell Biol. 29, 181-197. HEYN, A. N. J. (1969 Appl. Cryst. (1975), 8, 342] claim that the nucleation of stable forms of certain substances may preclude the subsequent preparation of previously known metastable crystalline forms 'often even in laboratories many miles away'. However, the literature on these substances does not indicate that any authentic metastable forms have ceased to be obtainable, and we see no reason to believe that the effects of seeding are other than local and temporary. References

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Pharmaceutical Product Stability

Webster¹

2010

Pharmaceutical Sciences Encyclopedia

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Pharmaceutical product stability may be defined as the capability of a particular formulation to remain within its physical, chemical, microbiological, therapeutic, and toxicological specifications while in a specific container closure system. There are many factors that can affect the stability of a pharmaceutical product. These include the stability of the active drug(s), interactions between active and inactive ingredients, the dosage form, manufacturing process, the container system, and environment for shipping, handling, and storage. This article focuses on the different types of pharmaceutical product stability, such as chemical degradation, physical degradation, and microbial degradation.

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Dehydration of Crystalline Theophylline Monohydrate and Ampicillin Trihydrate

Cited by 54 publications

References 4 publications

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Can metastable crystal forms `disappear'?

Pharmaceutical Product Stability

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