Solutol and cremophor products as new additives in suppository formulation

Our research has a double purpose. On the one hand, doctors have expressed the need to formulate a rectal suppository dosage form from diuretic ethacrynic acid, which would add to the choice of treatment methods and thereby increase the possibilities of individual cure. On the other hand, the liberation and thereby the bioavailability of poorly-soluble ethacrynic acid needs to be enhanced, and for this purpose solubility-increasing additives new to rectal therapy were used. Solutol HS 15, Cremophor RH 40, and Cremophor RH 60 were used as additives in concentrations of 1, 3, 5, and 10%. The quantity of drug released changed as a function of additive concentration. Depending on the acceptor phase, the best results were achieved with an additive concentration of 1-3%, which is related to the optimal additive quantity accumulated on the boundary surface.

In vitro and in vivo study in rats of rectal suppositories containing furosemide

The aim of our experimental work was to formulate furosemide-containing rectal suppositories, to study drug release with in vitro membrane diffusion examinations and to increase drug liberation with the use of non-ionic surfactants (Solutol HS 15, Cremophor RH 60, Montanox 60 DF), which were incorporated in the suppository base in various concentrations. Suppocire AS2X proved to be the best suppository base (diffused drug: 69.78%). The use of 1% Cremophor RH 60 additive with the Witepsol H 15 base increased the quantity of the diffused drug from 62 to 75%. The membrane diffusion examinations were followed by studying the influence of suppository bases and additives exerted on the actual diuretic effect in Sprague-Dawley male rats. Once again the Suppocire AS2X suppository base gave the best results compared to the control; the quantity of the animals' urine showed a fourfold increase. Used with the Witepsol H 15 base, even 1% of all the three additives resulted in a considerable increase of diuretic effect, so their use proved to be advantageous. The comparison of the membrane diffusion examinations with the in vivo diuretic effect reveals that in vitro drug release and the pharmacological effect usually showed the same tendency, that is a greater extent of in vitro furosemide release was associated with a greater quantity of rat urine.

Preformulation experiences and in vitro model studies with spironolactone-containing suppositories

The optimal suppository base for the formulation of rectal suppositories containing diuretic spironolactone was selected experimentally. Model studies were carried out about the effect of solubility-increasing additives on the release of the drug from the suppositories. During the in vitro examinations acceptor phases of different pH values were used, and both diffusion time and the number of samplings were changed. Among the lipophilic and hydrophilic suppository bases studied the hydrophilic Macrogolum 1540 was found to be optimal. The release and diffusion of spironolactone was the most favourable from these suppositories. During storage these suppositories remained stable and the values of release did not decrease significantly (p < 0.05).

[Comparison of in vitro model examinaitons with respect to drug release from suppositories]

9 lipophilic suppository bases with different physical-chemical parameters were examined. Buspiron-hydrochloride, an anxiolytic drug with good water-solubility was used--partly as a model--as a pharmacon, in a concentration of 10.0 mg/2.00 g. The rate and extent of in vitro drug release was monitored with static and dynamic methods. Kidney-dialysing membranes with various surfaces were used. The quantitative measurements were carried out spectrophotometrically and the amount of the diffused drug was determined at lambda = 298 nm. The mean values were calculated from 5 parallel measurements each time. The percentage values of in vitro relative availability revealed that the results of the two static diffusion studies did not differ significantly (p < 0.05) and were almost independent of the size of the membrane surface. The results of the dynamic diffusion method were well-reproducible but were vehicle-dependent. The process of release was characterized by the mathematical transformation of the release curves, while the correlation coefficients described the closeness of the relation. Two German vehicles, namely Witepsol H 15 with a medium hydroxyl value and Massa Estarinum 299, and a French vehicle, Suppocire AS2X were found to be excellent for the formulation of suppositories containing Buspiron-hydrochloride.

Bioavailability of acetaminophen containing suppositories in rats

An attempt was made to optimize the rectal delivery of acetaminophen (paracetamol). One of the aims was to determine which of the various lipophilic and hydrophilic suppository bases proved to be the best with respect to in vitro drug liberation. Among several experimental vehicles the Witepsol H 15 base with 10 of Miglyol 812 and the Macrogolum 1540 with 5% of Span 20 proved to be excellent. Furthermore, a well-known pharmacological effect of the paracetamol containing suppositories was evaluated in vivo in rats. The antipyretic response to the drug depends on the vehicle administered, showing an excellent correlation between in vitro and in vivo results.

[Experiences with the rectal use of a chemotherapeutic agent. 1. In vitro biopharmaceutical examinations; selection of the optimal vehicle]

The factors influencing in vitro liberation (Part 1) and in vivo absorption (Part 2) from trimethoprim-containing rectal suppositories and the authors' results related to them are reported in this two-part publication. Special emphasis was laid on selecting the optimal suppository base which is harmless physiologically yet not indifferent pharmacologically. From among the 24 compositions studied, a lipophilic mixture containing a surface active additive (Witepsol W 35) and a hydrophilic (Macrogolum) mixture were found to be the best in all respects. Liberation from the trimethoprim-containing rectal suppositories was measured with in vitro dynamic diffusion and spectrophotometrically. A power relation was found to exist between the quantity of the released pharmacon and the diffusion time, and a significant negative exponential relation was observed between the doses and their respective in vitro availability values.

[Experiences with the rectal use of chemotherapeutic agents. 2. Pharmacokinetic examinations with animals]

The aim of the investigations was to optimise vehicle for trimethoprim (TMP) suppositories ready for clinical trials. The rectal absorption of TMP was studied in anaesthetized rats. The drug liberation properties of the five mixed vehicles with promising in vitro results (Part 1.) were studied. The course of the blood level curves was monitored with serial sampling. The TMP concentration of blood was determined by bioassay. Individual bases were compared with the use of the pharmacokinetic parameters derived from the analysis of the obtained blood level curves, with special respect to biological availability (BA). The extent of bioavailability is influenced considerably by the hydro-, lipo- or lipohydrophilic property of the vehicle. TMP, if incorporated in the proper vehicle, is absorbed well. With three vehicles the extent of absorption exceeded the absorption seen with oral administration on the same model (BA = 38.8%). The best results were achieved with the lipophilic base Witepsol W 35 containing 10% of Polysorbate 20 and 10% of Polysorbate 61 (BA = 63.8%) and with Witepsol W 35 containing 10% of Polysorbate 60 (BA = 64.9%). The hydrophilic Macrogol 1540 vehicle containing 5% of Macrogol 400 had only slightly worse results (BA = 52.9%). In the case of the lipohydrophilic Witepsol W 35 vehicle with 10% of Polysorbate 20 and 10% of Polysorbate 61 content a significant negative exponential relation was found between the administered doses and their respective bioavailability values, this tendency had been observed during the in vitro examinations, too. No such relation was found in the case of the lipophilic Witepsol W 35 vehicle containing 10% of Miglyol 812.

Experiences with the rectal use of trimethoprim

The possibility of rectal use of trimethoprim was studied. The in-vitro liberation of the drug from 24 different suppository bases was examined and the results used to select bases for in-vivo examination. The in-vitro liberation from the suppositories containing 50-200 mg trimethoprim was studied by the method of dynamic diffusion, and the released drug content was measured spectrophotometrically. The in-vivo examinations were performed in anaesthetized rats. The concentration of trimethoprim in blood was determined by bioassay. The absorption of the drug in the form of oral suspension, rectal solution and suppository was also studied. The pharmacokinetic parameters obtained after blood-level curve fitting were compared by use of the MedUSA 1.6 program. The best in-vivo results were achieved with the lipohydrophilic Witepsol W 35 vehicle containing 10% polysorbate 20 and 10% polysorbate 61 (bioavailability = 63.8%) and with Witepsol W 35 containing 10% polysorbate 60 (bioavailability = 63.8%). The results for hydrophilic Macrogol 1540 vehicle containing 5% of Macrogol 400 were only slightly worse (bioavailability = 52.9%). In the case of the lipohydrophilic Witepsol W 35 vehicle with 10% polysorbate 20 and 10% polysorbate 61 content a significant negative exponential relationship was found between the administered doses and their respective bioavailability values; this tendency was also observed during in-vitro examinations. When incorporated in the appropriate vehicle trimethoprim was absorbed well. With three vehicles the extent of absorption exceeded that for oral administration on the same model (bioavailability = 38.8%). Trimethoprim rectal suppositories, which are formulated with the vehicles having the best in-vitro and in-vivo results, are suitable for clinical pharmacological investigation.

[Formulation and in vitro examination of furosemide-containing suppositories and preliminary experiences of their clinical use]

Rectal suppositories containing Furosemide (4-Chloro-N-furfuryl-5-sulfamoylanthranilic acid) and Furosemide Sodium were formulated with various suppository bases. The in vitro drug release of Massa Estarinum 299 proved to be the best from among the vehicles having various physical-chemical properties. The diuretic effect of the two suppositories was compared in a prospective, cross-over clinical trial including 8 patients. Both preparations have induced and increase of urine flow, which was comparable to the diuretic effect of the tablet. Thus the possibility of rectal use has been added to the modalities of therapeutic Furosemide administration.

Formulation and in vitro examination of furosemide containing suppositories and preliminary experiences of their clinical use

Rectal suppositories containing furosemide (4-chloro-N-furfuryl-5-sulfamoylanthranilic acid) and furosemide sodium were formulated with various suppository bases. The in vitro drug release of Massa Estarinum 299 proved to be the best from the vehicle having various physical-chemical properties. The diuretic effect of the two suppositories was compared in a prospective, crossover clinical trial including 8 patients. Both preparations have induced an increase of urine flow, which was comparable to the diuretic effect of the tablet.

[Production technology and in vitro study of rectal suppositories containing chloroquine phosphate]

Chloroquine-phosphate was suspended in various lipophilic and hydrophilic suppository bases in an amount of 250 mg/2.0 g. The authors studied the solidity and the disintegration time of the suppositories as well as the in vitro drug liberation with a membrane diffusion method. The effect of the storage time and the storage circumstances on the stability of the suppositories was observed. Tropics-resistance studies were also carried out at a temperature of 45 degrees C and at a relative humidity content of 75%, thus these suppositories may be used for the treatment of malaria. The Witepsol H 15 base was found to be the best in all respect for use in countries with a continental climate. Finally a function relationship was found between the concentration of the pharmacon and the diffusion time with linear regression analysis.

Formulation and in vitro study of antibacterial vaginal suppositories

Vaginal suppositories frequently used in gynaecological therapy were studied. Several antibacterial pharmacons are used for the topical treatment of vaginitis of various origins. In view of the fact that the liberation of the given active substance and the subsequent therapeutic effect may be improved or inhibited by the vehicle, our aim was to find the optimal suppository base for vaginal suppositories containing sulfadimidine, chloramphenicol and gentamicin sulfate by means of in vitro experiments. On the basis of breaking hardness, disintegration time and spreading properties the French Suppocire NA product, and compositions of macrogols with lower molecular weight proved to be the best lipophilic and hydrophilic bases, respectively. Among the lipophilic bases the in vitro drug liberation of Suppocire NA was significantly better (P < 0.05) than the other lipophilic bases. This vehicle is recommended for the topical treatment of vaginitis, as these suppositories have the further advantage that they can easily be produced on a magistral, galenical or industrial scale as well.

Formulation of diazepam containing rectal suppositories and experiences of their biopharmaceutical study

Methodology and the results of the in vitro membrane diffusion and in vivo bioavailability studies are presented. The results confirm a correlation between in vitro and in vivo findings. Hydrophilic macrogol-mixture with great molecular mass can be recommended as the optimal vehicle for formulation of diazepam suppositories.

[Acetaminophen-containing suppositories in vitro and in vivo]

Rectal suppositories with a paracetamol content of 300 mg were prepared and the optimal vehicle was searched for experimentally. 9 different kinds of lipophilic, lipohydrophilic and hydrophilic vehicles were used for this purpose. Research was focused on determining the factors influencing in vitro drug liberation. The suppository compositions which proved to be the best by the membrane diffusion method were tested by in vivo animal experiments with respect to their antipyretic effect. The in vitro and in vivo results were evaluated statistically and some of the suppository bases showed significant differences. In the authors' opinion the optimal vehicle for the preparation of paracetamol-containing suppositories is the Witepsol H 15 suppository base containing 10% Miglyol 812 (neutral oil).

[Formulation of diazepam suppositories, results of rheological and biopharmaceutical studies. 1. Rheological study of the used suppository bases]

The rheological properties of four lipophilic and three hydrophilic suppository bases were studied. The flow and viscosity curves, the initial, equilibrium and plastic viscosity as well as the Bingham's yield value of the systems were determined. It was found that the viscosity curves had two different parts in the examined shearing rate range: the part of greater rise described a definitive destruction of the system, while the part of smaller rise represented an equilibrium state. The values of the rheological parameters of the lipophilic and hydrophilic systems showed a definite difference, which was explained by the greater association of the hydrophilic bases.

[Formulation of diazepam suppositories, results of rheological and biopharmaceutical studies. 2. In vitro membrane diffusion and in vivo absorption results]

In the first part of the publication the rheological properties of the vehicles used for the production of suppositories were studied in order to determine the ideal parameters for formulation. In this part a detailed methodology and the results of the in vitro membrane diffusion and in vivo bioavailability studies, are presented. The results confirm a general correlation between the in vitro and the in vivo findings. It seems that hydrophilic macrogol-mixture with great molecular mass can be recommended as the optimal vehicle for formulation of diazepam suppositories.

[Formulation and in vitro investigation of antibacterial vaginal suppositories. Part 1. Considerations in selecting the vehicle. Methods and results of the physical examination]

Vaginal suppositories frequently used in gynaecological therapy were studied. Several antibacterial pharmacons are used for the topical treatment of vaginitis of various origins. However, the choice of the vaginal suppository base was often considered to be of minor importance for a long time. In view of the fact that the liberation of the given active substance and the subsequent therapeutic effect may be improved or inhibited by the vehicle, their aim was to find the optimal suppository base for vaginal suppositories containing sulphadimidine, chloramphenicol and gentamicin-sulphate by means of in vitro experiments. On the basis of breaking hardness, disintegration time and spreading properties the French Suppocire NA product, and compositions of macrogols with lower molecular weight proved to be the best lipophilic and hydrophilic bases respectively.

[Formulation and in vitro investigation of antibacterial vaginal suppositories. Part 2. In vitro membrane diffusion and microbiologic studies]

After the physical parameters had been determined, the in vitro drug liberation from vaginal suppositories containing 100 mg of antibacterial agent (sulphadimine, chloramphenicol, gentamicin-sulphate) was studied by membrane diffusion and microbiological methods. Among the vehicles available in Hungary the hydrophylic Massa macrogoli was found to be the best for this purpose. Among the lipophilic bases the in vitro drug liberation of the French Suppocire NA product was significantly better (p < 0.05) compared to the other lipophilic bases. This vehicle is recommended by the authors for the topical treatment of vaginitis, as these suppositories have the further advantage that they can easily be produced on a magistral, galenical or industrial scale as well. In the first part of the publication the formulation and some important physical parameters of lipophilic and hydrophilic antibacterial suppositories for vaginal use were described. In the present paper the drug liberation ability of the compositions with proper physical parameters was studied. The published results were obtained from measurements performed 1 week after formulation.

[Formulation and analysis of suppositories containing papaverine hydrochloride. Part 2. In vitro membrane diffusion studies]

Rectal suppositories with 0.10 g/2.0 g Papaverine hydrochloride content were made with 12 different vehicles. The membrane diffusion method was used to study the factors influencing the in vitro drug liberation. The Polysorbate 20 and 61 tenside pair, the optimal concentration of which was 5% each, was found to influence diffusion favourably. Neutral oils softening the consistency (Miglyol 812 and Estasan), similarly in 5%, also had a favourable effect on the in vitro diffusion by increasing the spreading properties. As to the lipophil suppository masses with high and low hydroxyl numbers, only the latter could be used favourably. The 6-month-long storage resulted in drug retention in several experimental series. Correlation was found in several cases between the physical parameters of the suppositories and their in vitro drug liberation. Finally, with the help of linear regression calculation and in view of the in vitro relative bioavailability values the optimal vehicle is suggested for the formulation of suppositories containing Papaverine hydrochloride. The triglyceride type Estaram 299 was found to be the most suitable in every respect, either in itself or combined with 5% neutral oil.

[Formulation and analysis of suppositories containing papaverine hydrochloride. Part 1. Choice of the optimal vehicle and determination of the physical parameters of the suppositories]

Suppositories containing 0.10 g papaverine hydrochloride were made with moulding technology to produce spasmolytic effect. The optimal vehicle was tried to be found for these suppositories. During the experiments 12 different suppository masses were used, including lipophil and lipohydrophil vehicles as well as vehicles with low and high hydroxyl numbers. Five different kinds of physical parameters were determined: melting and drop points, disintegration and special penetration times and breaking hardness. The physical parameters of suppositories without active substance and containing papaverine were examined separately. After 6 months of storage the greater part of the masses showed unfavourable changes (after-hardening, increase of the disintegration time, etc.). In the end the Estaram 299 mass, a triglyceride type of mass with a low hydroxyl number was found satisfactory in every respect, either in itself or combined with 5% Estasan neutral oil.

[Biopharmaceutical importance of pharmaceutical aids in drug prescribing with special reference to rectal administration]

Based on literary sources, the medical and pharmaceutical significance of vehicles and additives, which play an ever-increasing role in the production of all drug forms, is discussed. Then the groups of additives used in the production of suppositories are described partly on the basis of our own experiences, and their biopharmaceutical significance is evaluated.