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PubMed1999

Lack of pediatric drug formulations.

Many drugs frequently used in infants and young children are not available in suitable dosage forms. Liquid dosage forms must be prepared extemporaneously, while using appropriate excipients. However, it is critical to determine the stability of various drugs at clinically important concentrations and practical storage conditions. It is of concern that few funding agencies are willing to support research on the development of stable liquid dosage forms for pediatric patients. The need for such data will continue, because it is unlikely that all drugs approved for adults will also be labeled simultaneously for potential use in infants and children. Presentations and publications on stable drug formulations will offer the opportunities for pediatric patients to receive the desired drugs and doses most effectively and safely.

Adult↗
PubMed2006

Profiling in vitro drug release from subcutaneous implants: a review of current status and potential implications on drug product development.

This review presents current methods and strategies for studying the release characteristics of drugs from subcutaneous implant dosage forms. Implants are dosage forms that are subcutaneously placed with the aid of surgery or a hypodermic needle, and are designed to release drugs over a prolonged period of time. In most cases, the objective of a release test is to identify sufficiently discriminatory procedures that in turn would provide data to set meaningful specifications. Additional information obtained from successful in vitro-in vivo correlations (IVIVC) and accelerated drug release tests are extremely useful during drug product development. Although several workers have employed different methods to monitor drug release from these dosage forms, the use of the compendial Apparatus 4 (flow-through) device has been recommended in a publication on FIP/AAPS Guidelines for drug release testing of modified release dosage forms. However, most of method development with this device has focused on oral immediate or controlled release dosage forms and little published information is available on implants. Two recent reports on workshops provide useful information on methods to evaluate drug release from controlled-release parenterals such as implants, including IVIVC and accelerated release testing. Details on such studies, however, are generally not found in the literature; possibly because of the high proprietary value of methodologies for establishing release specifications of implant dosage forms. This article reviews the current status of methodologies used in the investigation of drug release from subcutaneous implants with an emphasis on mechanistic, product development and regulatory perspectives.

Drug Design↗
PubMed2006

A simplified weight-based method for pediatric drug dosing for zidovudine and didanosine in resource-limited settings.

BACKGROUND: Zidovudine and didanosine are antiretroviral drugs used for human immunodeficiency virus (HIV)-infected children with dose recommendations based on body surface area calculations. Although weight and height can both be measured, it may be impractical to expect providers in resource-limited settings to estimate accurately body surface area. METHODS: We developed an antiretroviral dosing chart based on authoritative sources for brand name drugs in weight bands (ie, 5-6.9, 7-9.9, 10-11.9, 12-14.9, 15-16.9, 17-19.9, 20-24.9, 25-29.9, 30-34.9 and 35-40 kg) to assist proper dosing of antiretrovirals for HIV-infected children in resource-limited settings. For drugs dosed by body surface area, we estimated likely weights and heights for age using standardized US growth charts for girls from which doses in weight bands were calculated. For this analysis, we calculated the difference between weight-based doses and body surface area-based doses for zidovudine 10 mg/mL oral solution, zidovudine 100-mg capsules, and didanosine 25, 50 and 100-mg chewable tablets using actual heights and weights from HIV-infected children in Africa and Romania. RESULTS: We used 1752 observations from 826 HIV-infected children (48% girls) from 9 countries. A total of 454 observations were in children <20 kg and 1298 > or =20 kg. For those <20 kg, the median difference of the weight-based dose as compared with the body surface area-based dose for zidovudine solution was -6.4% (range, -22.6, +13.7), zidovudine capsules +3.1% (range, -38.8, +44.7), didanosine chewable tablets +0.7% (range, -24.4, +22.5); for those > or =20 kg for zidovudine solution was 0.0% (range, -16.4, +11.8), zidovudine capsules +7.6% (range, -16.4, +36.9) and didanosine chewable tablets +1.2% (range, -16.4, +14.1). The dose precision for children <20 versus > or =20 kg was different for zidovudine solution (P < 0.001) and zidovudine capsules (P < 0.001), but not didanosine chewable tablets. The frequency that weight-based dose was more than 20% less than the body surface area-based dose for those <20 kg was 1.3% for zidovudine solution, 27.2% for zidovudine capsules and 4.9% for didanosine chewable tablets. For those > or =20 kg, the weight-based dose was never more than 20% less than the body surface area-based dose. CONCLUSION: Dosing zidovudine and didanosine by weight band provides reasonably precise dosing as compared with body surface area-based doses. However, use of zidovudine capsules in children <20 kg results in under dosing by >20% in many instances. Didanosine chewable tablets allow for higher dosing precision compared with zidovudine capsules because of increased flexibility in the dosage form. Solid dosage forms of antiretroviral medications designed specifically for children are urgently needed.

Adolescent↗
PubMed1987

Activated carbon particles as anti-cancer drug carrier into regional lymph nodes.

The effect of a new dosage form for anti-cancer agents was studied on tissue distribution and compared with the aqueous solution form. The new dosage form, developed in order to distribute a greater amount of the agent to regional lymph nodes, comprises polyvinylpyrrolidone and small activated carbon particles adsorbing pepleomycin (PEP-CH) or mitomycin C (MMC-CH) in saline. Pepleomycin at 500 micrograms/kg or mitomycin C at 250 micrograms/kg were injected into the gastric wall of dogs in the new dosage form or the aqueous solution form. The activity level of the agents in tissues was bioassayed within 24 h after injection by the thin agar plate method. Statistically, the new dosage form maintained an activity level in lymph nodes that was significantly higher than the aqueous solution form (ratio of PEP-CH to solution form, 6-32 times in 24 h; MMC-CH, 100-1000 times in 6 h; p less than 0.05-0.01), and a concentration in blood that was significantly lower (PEP-CH, about 1/2 times in 2 h; MMC-CH, 1/10-1/5 times in 1 h; p less than 0.05).

Animals↗
PubMed1985

Bioadhesive polymers as platforms for oral controlled drug delivery III: oral delivery of chlorothiazide using a bioadhesive polymer.

Bioadhesive polymers that bind to the gastric mucin or epithelial cell surface are useful in drug delivery for the purposes of (a) retaining a dosage from in the GI tract and (b) increasing the intimacy and duration of contact of drug with the absorbing membrane. Polycarbophil has previously been shown to have bioadhesive properties in the rat stomach and small intestine and was employed in the present study with a sustained-release delivery system to demonstrate improved drug delivery. Using chlorothiazide as the model drug, drug containing albumin beads were prepared and used as the sustained-release system. The beads were physically mixed with equally sized particles of polycarbophil and placed in a capsule to produce a bioadhesive dosage form. When the dosage form contacts the stomach, the gelatin capsule dissolves, exposing the polycarbophil to the bathing fluid. The bioadhesive polymer rapidly hydrates, retaining the albumin beads and attaching to the mucin coating of the stomach. Plasma drug levels in rats showed a longer duration of action and greater bioavailability for the bioadhesive dosage form than for either albumin beads or drug powder alone. The results suggest that the principle of bioadhesion can significantly improve therapy, due to a reduced rate of gastric emptying, an increase in contact time, and the intimacy of contact of the drug with the absorbing membrane.

Acrylic Resins↗
PubMed2006

Critical freezing rate in freeze drying nanocrystal dispersions.

Recent advances in nanoparticle technologies have significantly enhanced the oral and parenteral delivery of poorly water-soluble active pharmaceutical ingredients (APIs). However, reports have been limited on the various drying procedures to convert a liquid nanocrystal dispersions into solid dosage forms. The solid dosage form should consist of nanocrystals that can readily reconstitute into their original size upon dissolution in water. Herein, the freeze drying process of nanocrystal dispersions was examined at varying freezing rates (speed of freezing interface). As freezing rate decreases, more particle-particle aggregation developed. A critical freezing rate, below which the dried nanocrystals cannot be re-dispersed, was identified based on the plot of the particle size of reconstituted nanocrystals versus freezing rate. Freeze drying at a freezing rate near the critical value produces dry powders of bimodal particle size distribution after re-dispersion. In addition, API concentration was found to significantly affect the critical freezing rate and therefore the re-dispersibility of dry powders. The concept of critical freezing rate is critical for the development of solid dosage forms of liquid nanocrystal dispersions.

Crystallization↗
PubMed1994

Evaluation of the correlation between in vivo and in vitro release. Effect of the force of contraction and food on drug release.

The effects of the force of contraction in the gastrointestinal (GI) tract and of food on drug release were investigated. Two dosage forms were administered orally to beagle dogs. Dosage form A was a matrix in which drug release was affected by the force of contraction in the GI tract, and dosage form B was not affected by the contraction force. The in vitro dissolution curves from dosage forms A and b using the paddle-beads method were similar to in vivo drug release, with the respective release of up to at least 50%. The in vitro release by means of the paddle-beads method was characterized by the in vivo drug release. The in vivo drug release profile from dosage form A was affected by food. A 1:1 relationship between in vivo and in vitro release was observed up to 6 h in those dogs under the fed condition, but only up to 2.5 h in those under the fasted condition. In the earlier stage of oral administration there was no difference in drug release profile between dogs of the fed and fasted conditions; however, the drug release rate in the fed condition was faster than that in the fasted condition 2-4 h after administration. It was thus assumed that in the fed condition, drug release from dosage form A was affected by gastro-duodenal transit time or by the different environment in the distal parts of the GI tract rather than by the force of contraction.

Administration, Oral↗
PubMed2005

Topical drug classification.

Current definitions of lotions, gels, creams and ointments vary depending on literature source, market history or traditional use. This often leads to confusion when deciding which dosage form to prescribe and/or purchase. The existing classification of topical dosage forms needs to be re-examined to ensure that definitions for different dosage forms are based on consistent scientific principles and that dosage forms can be distinguished from one another. The purpose of this study is to obtain a scientifically based, systematic classification of dosage forms for topical drugs. A variety of prescription and over-the-counter topical products currently marketed as lotions, gels, creams, and ointments are evaluated using different techniques including rheology (viscosity and shear rate versus shear stress), loss on drying (LOD), specific gravity, surface tension, thermogravimetric analysis (TGA), water absorption, dilution properties, microscopic evaluation, transmittance of visible light, appearance and composition. Rheology is the most discriminating property separating creams and lotions. Water plus volatiles (as measured by LOD) and composition separate ointments and creams. Composition and thermal behavior separate gels from the other dosage forms. Based on these findings, new definitions and a decision tree are presented to assist in the determination of the appropriate nomenclature for a topical dosage form.

Administration, Topical↗
PubMed1987

Nifedipine gastrointestinal therapeutic system.

Convenient once-a-day dosage regimens are highly desirable in general, and especially for the treatment of asymptomatic diseases such as essential hypertension. Nifedipine is an insoluble, short-acting calcium channel blocker that presents a difficult technical challenge for formulation in a constant 24-hour delivery dosage form. Once-a-day dosage forms have been developed based on the gastrointestinal therapeutic system (GITS) push-pull osmotic pump configuration in three strengths with different drug delivery rates (mg/hour) per dose (mg), as 1.7/30, 3.4/60, and 5.1/90. The delivery rates of drug from these systems are controlled by their drug loading, composition of osmotic components, membrane properties, and dimensions. The release rates are independent of pH in the range from gastric pH = 1.2 to intestinal pH = 7.5. The release rates are independent of stirring rate and therefore unlikely to be influenced by motility in the gastrointestinal tract. The drug release rate from the nifedipine GITS dosage form in vivo in the gastrointestinal tract of dogs has been found to be equal to the release rate in vitro, indicating that the in vitro test is predictive of in vivo delivery. Following administration of the nifedipine GITS dosage forms to human subjects, absorption rates, calculated from resulting plasma concentrations, indicate that the cumulative amount of drug absorbed in humans over 24 hours is proportional to the amounts of drug delivered in vitro. Plasma concentrations are therefore predictable and remain relatively constant throughout the 24-hour dosing interval.

Animals↗
PubMed1995

Pharmacokinetics and relative bioavailability of selegiline in healthy volunteers.

Selegiline is beneficial to Parkinsonian patients as an adjunct to levodopa therapy. A sensitive flourimetric assay based on inhibition of rat brain monoamine oxidase-B (MAO-B) in vitro has been developed to study the pharmacokinetics of selegiline. This method quantitates selegiline as low as 0.25 ng ml-1. The pharmacokinetics and relative bioavailability of selegiline were investigated in healthy volunteers following oral administration of 10 mg tablet or solution. A half-life of approximately 70 min was observed following the administration of either dosage form. Although the two dosage forms exhibited a lag time, the absorption was rapid and peak plasma concentrations were observed between 30 and 45 min for the solution and 30 and 90 min for the tablets. Statistically no significant difference was found between Cmax, Tmax, AUC0-infinity and MRT between the two dosage forms. Negligible renal clearance was found in both groups, but apparent oral plasma clearance was comparatively high and indicates rapid elimination of selegiline from the body.

Adult↗
PubMedDate not supplied

Spectrophotometric and some thermodynamic parameters of the charge transfer complexation between chloranilic acid and chlorpheniramine.

The principle of charge transfer complexation involving a pi-acceptor (chloranilic acid) and an n-donor (chlorpheniramine) was utilized in the assay of the later in its pure form and in its tablet dosage forms. Some thermodynamic parameters of the complex such as association constant (Kc), molar absorptivity (epsilon c), free energy change (delta G degree), enthalpy (delta H degree) and entropy (delta S degree) changes were determined to establish the stability of the complex and the optimum conditions for the complex formation. The values obtained for these thermodynamic parameters indicated that the complex formed between this two chemical entities is highly stable. Assay of chlorpheniramine in its pure form and in its tablet dosage forms gave high percentage recoveries. The principle of charge transfer complexation could therefore be employed in the colorimetric assay of chlorpheniramine in its tablet dosage forms.

Benzoquinones↗
PubMed2003

[Advances in the research on targeted preparations of traditional Chinese medicine and natural drugs].

OBJECTIVE: Targeting dosage form is a kind of targeting drug delivery system which can be used to lock drugs aroud the target organs, tissues, cells and obtain more effective treatment for dose concentration, thus reducing the side-effects of such drugs while increasing their effeciveness. Targeting dosage form is the fourth-generation drug dosage form and it is ideal system for administration because it release the theraping drugs in the targeting-site. Particular emphasis was placed on liposome due to it was used as a drug carrier. Meanwhile, the highlights of research were on magnetic and enzyme targeting preparations. In addition, oral colon targeting drug delivery system, drugs were carried to ileocecum and release to get local and whole effect, is also an important part of targeting dosage form. The study on traditional chinese medicine (TCM) targeting dosage form is still at beginning stage in China. At present, most of study on TCM and natural products targeting drugs were focus on simple effective component and merely on TCM effective positions in relative with the difficult for determing their quality standard and procedure of preparing. It is the kernel item for TCM modernization and the key for TCM internationalization to develop new dosage form and new technology of TCM. There is a need in collaboration with multiple discipline. It will be a important research subject to develop TCM targeting preparation in the near future. TCM targeting dosage form can be classified into liposome, nanoparticles, multiple emulsion etc according to the difference of carrier and oral, rectal, colonic, nasal, dermal, ocular system on a basis of administration and so on. This paper made a summary on TCM and natural products targeting dosage form according to different targeting positions and introduce the procedure of preparing compared with the effect in vivo and manifest that TCM and natural products targeting dosage form will have good exploit prospect.

Drug Carriers↗
PubMed1977

Vehicle effects on activity of an anticonvulsant compound.

The effect of several lipid and nonlipid pharmaceutical solvents on the in vivo activity of 1-diphenylmethyl-4- [(6 methyl-2-pyridyl) methyleneamino] piperazine (I) was evaluated in the mouse. The intensity of onset and the duration of anticonvulsant activity of the compound were affected depending on th type and form of liquid dosage preparation used. The rate of decline in anticonvulsant activity in the 80-20% response range followed apparent zero-order kinetics. A linear relationship between the observed ED50 and the concentration of sorbitol in the dosage form of I was observed. A reduction in the sorbitol content of the dosage form resulted in a proportional increase in the rapidity of onset and the duration of anticonvulsant activity of I. Emulsification restored both the onset and duration of pharmacological activity, which was virtually arrested when the compound was given orally as a solution in oil.

Animals↗
PubMed1995

Novel oral medication delivery system for famotidine.

A famotidine wafer that rapidly disperses on the tongue without water is a novel alternative to other histamine2 (H2)-antagonist dosage forms. Benefits associated with such a dosage form include convenience and potentially improved compliance for patients who dislike or have difficulty taking tablets and capsules. This report describes the research of three studies on the famotidine wafer dosage form. In the first trial, the bioequivalence and tolerability of the new 40-mg famotidine wafer and the marketed 40-mg famotidine tablet were studied in a 2-period crossover study (n = 18). The two formulations were bioequivalent as assessed by area under the plasma concentration versus time curve and maximum plasma concentration of famotidine. The plasma concentration of famotidine associated with 50% inhibition of pentagastrin stimulated gastric acid secretion (EC50; 10 ng/mL) was attained on average within 0.5 hours post-dose for the wafer and tablet. In a second trial, the tolerability of the famotidine 20-mg and 40-mg wafers or placebo given twice daily (bid) for 14 days were evaluated (n = 192). Both wafer strengths were well and equally tolerated. In a third trial of 450 subjects, the 40-mg wafer was preferred over tablets by 75% of the subjects, when they were asked to consider the method of administration and flavor. When used as an alternative to tablets and other conventional dosage forms, the wafers have the potential therapeutic benefit of improved compliance. It is concluded that similar systemic exposure, excellent tolerability, palatability, and preference make the famotidine wafer a clinically acceptable and convenient dosage from for patients on H2-antagonist therapy.

Administration, Oral↗