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Formulation of medicines for children.

The development of age-adapted dosage forms and taste-masking of bitter-tasting drugs administered orally for children, are formidable challenges for formulation scientists. Childhood is a period of maturation requiring knowledge of developmental pharmacology to establish dose but the ability of the child to manage different dosage forms and devices also changes. Paediatric formulations must allow accurate administration of the dose to children of widely varying age and weight. Whilst the oral route will be preferred for long term use and the intravenous route for the acutely ill, many of the dosage forms designed for adults, such as oro-dispersible tablets, buccal gels and transdermal patches, would also benefit children if they contained an appropriate paediatric dose. The age at which children can swallow conventional tablets is of great importance for their safety. Liquid medicines are usually recommended for infants and younger children so the ability to mask unpleasant taste with sweeteners and flavours is crucial. More sophisticated formulations such as granules and oro-dispersible tablets may be required but there will be limitations on choice and concentration of excipients. There are many gaps in our knowledge about paediatric formulations and many challenges for the industry if suitable preparations are to be available for all ranges. A CHMP points to consider document is soon to be released. More research and clinical feedback are important because a formulation with poor acceptability may affect compliance, prescribing practice and ultimately commercial viability.

Adolescent↗

[Results of creating domestic medicinal forms of antineoplastic agents at the N. N. Blokhin Cancer Research Center of the Russian Academy of Medical Sciences].

Since there is a rise in morbidity and mortality rates due to malignant neoplasms, their drug therapy along with radiation and surgical methods remains a burning problem of modern medicine. Empirical and rational approaches to searching for new drugs have given rise to cancer agents that are widely used in clinical practice today. By taking into account the chemical and biological features of experimentally chosen active cytostatics, emphasis should be laid on the particular importance of development of effective dosage forms of antitumor substances by conducting chemical analytical, pharmacological engineering, biopharmaceutical, and pharmacokinetic studies. The purpose of the present paper is to assess the retrospective and present status of studies to design dosage forms of cancer drugs in our and foreign countries, and to pool the results of the author's own studies in designing dosage forms of antitumor substances from classes of chloroethylamines, nitrosoalkyl ureas, complex metal compounds, anthracene diones, antibiotics of plant origin, etc.

Academies and Institutes↗

Absorption of phenobarbital from tablets and elixir.

A three-way crossover study was conducted with 24 healthy male volunteers to determine the relative bioavailability of four different 100-mg phenobarbital tablets compared with a reference elixir. Each subject received two of the tablets and the elixir at 30-d intervals. Blood samples were collected daily for 19 d after each dose. Plasma phenobarbital concentrations achieved with the five dosage forms differed by less than 20% within 2-3 h after dosing. The extent of absorption for all dosage forms, as determined from area under the plasma concentration-time profiles, were within 10% of each other. The peak plasma concentration was the greatest and the time to peak concentration was the shortest for the elixir. One of the tablets exhibited a time to peak concentration of 8.6 h, which was significantly longer than any of the other dosage forms. The time to peak concentration correlated with the percent of drug dissolved in 60 min, as determined in 0.1 M HCl, using the USP XX paddle method at 50 rpm.

Adult↗

Drug delivery systems improve pharmaceutical profile and facilitate medication adherence.

Innovations in dosage forms and dose delivery systems across a wide range of medications offer substantial clinical advantages, including reduced dosing frequency and improved patient adherence; minimized fluctuation of drug concentrations and maintenance of blood levels within a desired range; localized drug delivery; and the potential for reduced adverse effects and increased safety. The advent of new large-molecule drugs for previously untreatable or only partially treatable diseases is stimulating the development of suitable delivery systems for these agents. Although advanced formulations may be more expensive than conventional dosage forms, they often have a more favorable pharmacologic profile and can be cost-effective. Inclusion of these dosage forms on drug formulary lists may help patients remain on therapy and reduce the economic and social burden of care.

Dosage Forms↗

Bioavailability of sulfadiazine solutions, suspensions, and tablets in humans.

A four-way crossover sulfadiazine bioavailability study was conducted in 16 normal healthy male volunteers. The subjects were divided into groups of eight. Each group received four different oral dosage forms of sulfadiazine at 1-week intervals: a solution as a reference, a suspension, and two different tablets. All dosage forms were equivalent to 500 mg of sulfadiazine. Blood samples were obtained at 0, 0.5, 1.0, 2.0, 3.0, 4.0, 6.0, 8.0, 10.0, 25.0, 33.0, and 49.0 hr. Analysis of variance indicated no statistically significant difference (p more than 0.05) between the dosage forms in terms of area under the plasma level--time curve, peak plasma concentration, and time of peak plasma concentration. In both groups, there were differences between products at isolated sampling times. It was concluded that the four tablet formulations of sulfadiazine exhibited bioavailability characteristics equivalent to those of the solution and the suspension.

Administration, Oral↗

Ranitidine hydrochloride: development of an isocratic stability--indicating high-performance liquid chromatographic separation.

The development of a stability-indicating assay for ranitidine hydrochloride using a mobile phase added ion-interaction reagent was achieved. The assay easily separated all known and unknown impurities/degradants. This assay may be used for the determination of purity, identity and strength for the active ingredient and finished dosage forms. Placebo samples were analyzed for all of the dosage forms and did not interfere with the separation. The system was found to be linear over a range of 0.056 to 44.4 microg/g, with a limit of detection of 0.028 microg/g and a limit of quantitation of 0.056 microg/g. The system precision was determined to be 0.7%. The development of the stability-indicating assay and the effect that each chromatographic variable had on the separation will be discussed.

Calibration↗

[Solid-state stability and preformulation study of a new parenteral cephalosporin antibiotics (E1040)].

In designing the dosage form, one major factor controlling their physicochemical properties is solid forms of the drug powder. The method for improving the physicochemical stability of unstable beta-lactam antibiotics is very important. E1040 is a novel parenteral 3-betaine type cephalosporin which has a broad antibacterial spectrum and potent activities against Citrobacter, freundii, Enterobacter cloacase, and glucose-non-fermentative bacteria, including P. aeruginosa. The present study was intended to provide the solid-state chemical stability of perenteral steril dry dosage form of E1040. The chemical stability differences among the various solid forms, dry amorphous, additive freeze dried amorphous solid and crystalline powder, were evaluated as a function of temperature by thermo stress tests. Freeze dried anhydrous amorphous form was the first steril dry dosage form investigated during the preformulation study. However, this compound is chemically unstable, in the titer of them, reduction are observed in the freeze dried amorphous solid. In order to select the most suitable solid form of E1040, two methods were used. One was crystalline solid and the other was NaCl additive freeze-dried formulation. Through our experiments, the solid-state chemical stabilization can be achieved by these two methods (effect of crystal structure and effect of NaCl additive).

Adjuvants, Pharmaceutic↗

Investigation on physicochemical and biological differences of cefpodoxime proxetil enantiomers.

Cefpodoxime proxetil (CP) is a prodrug of cefpodoxime acid (CA), and is supplied as racemic mixture of R- and S-enantiomers. CP has only 50% absolute bioavailability, and the reasons responsible for low bioavailability remain poorly understood. The present work ascertains physicochemical and biological properties of individual isomers of CP and explores their capacity to optimize delivery of CP. Both isomers showed similar pH stability behavior, but R-isomer was more susceptible to enzymatic metabolism compared to S-isomer, when incubated with enzymes collected from various segments of GIT. Based on the in vitro and in vivo results, use of S-isomer for development of a dosage form such as gastro-retentive dosage form can improve oral bioavailability of CP.

Administration, Oral↗

Selective spectrofluorimetric determination of phenolic beta-lactam antibiotics through the formation of their coumarin derivatives.

A simple, sensitive and selective spectrofluorimetric procedure was developed for the determination of amoxycillin, cefadroxil and cefoperazone. The method is based on the reaction between these drugs and ethyl acetoacetate, in acidic medium, to give yellow fluorescent products with excitation wavelengths ranging from 401 to 467 nm and emission wavelengths ranging from 465 to 503 nm. The reaction conditions were studied and optimized. The reaction obeyed Beer's law over the range of 10.0-20.0, 1.5-1.0 and 50.0-100.0 microg ml(-1) for amoxycillin, cefadroxil and cefoperazone, respectively. Interference's from other antibiotics, drugs and dosage forms additives, in capsules and vials dosage forms, were investigated. The proposed method was applied to the analysis of pharmaceutical formulations (capsules and vials) containing the above antibiotics, either alone or in combination with other antibiotics or drugs. The validity of the method was tested by the recovery studies of standard addition which were found to be satisfactory. The results of the proposed method demonstrated that the method is equally accurate, precise and reproducible as the official methods (USP XXIII) and those published for the non-official binary mixtures.

Amoxicillin↗

Review of alterations in oral phenytoin bioavailability associated with formulation, antacids, and food.

Since 1938, phenytoin has been widely used for the control of seizure disorders. Phenytoin is available from a variety of manufacturers in a variety of dosage forms. Certain physiochemical properties of phenytoin may lead to bioavailability changes. The physiochemical properties exert themselves not only in the presence of other drugs but also during the manufacturing process. Manufacturing processes that may influence phenytoin bioavailability include salt form, particle size, product excipient, and dosage form. Drug influences upon phenytoin bioavailability largely include antacid anions, which may form insoluble complexes. Anions present within the diet may also influence the rate and extent of phenytoin absorption. This article reviews the various influences on phenytoin bioavailability with regard to the manufacturing process, antacid, and food.

Administration, Oral↗

Targeting in the gastrointestinal tract: new approaches.

Most drug products are administered via the alimentary canal; prominent are the dosage forms which are swallowed, i.e., p.o. dosage forms, followed by those administered within the oral and the rectal cavities. The innermost surface of the alimentary canal is the epithelial lining which is void of keratinized superficial layers. The epithelium at both ends of the canal, i.e., oral cavity and esophagus, and anal canal is a multilayered (20-50 layers) stratified squamous epithelium, whereas that of the rest of the canal, i.e., gaster, small and large intestine and rectum is a single layer of columnar cells. The drainage is via both venous blood capillaries and lymphatic vessels. Blood drainage from the oral cavity and the lower end of the rectum is directly into systemic circulation via the vena cava. From the GI tract, however, the blood quantitatively passes through the portal vein and liver, hence is available for first-pass effect prior to entering systemic circulation. Targeting can be approached from two angles: 1) to exert the pharmacologic response at a specific site, or 2) to utilize a specific site for drug absorption. Targeting utilizes the anatomic, histologic, physiologic and biochemical features of various segments within the alimentary canal, paired with the design of special drug delivery systems or devices, and the use of special vehicle substances, such as polymers, bioadhesives, sorption promoters, or chemical modification (pro-drug) of the active moiety. Numerous examples of new types of drug delivery systems are presented. Many novel drug delivery systems discussed are still in experimental stage and evaluation, or even in the conceptual stage. However, it is anticipated that they all will contribute to further advancement in optimizing drug therapy.

Animals↗

Hypogonadism in men consuming sustained-action oral opioids.

Naturally occurring opiates (endorphins) diminish testosterone levels by inhibiting both hypothalamic gonadotrophin releasing hormone production and testicular testosterone synthesis. Heroin addicts treated with a single daily dose of methadone and nonaddicts receiving continuous intrathecal opioids quickly develop low luteinizing hormone and total testosterone levels. A similar pattern was sought in men consuming commonly prescribed oral opioids. Free testosterone (FT), total testosterone (TT), estradiol (E(2)), dihydrotestosterone (DHT), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were measured in 54 community-dwelling outpatient men consuming oral sustained-action dosage forms of opioids several times daily for control of nonmalignant pain. Hormone levels were related to the opioid consumed, dosage and dosage form, nonopioid medication use, and several personal characteristics and were compared with the hormone analyses of 27 similar men consuming no opioids. Hormone levels averaged much lower in opioid users than in control subjects in a dose-related pattern (P < .0001 for all comparisons). FT, TT, and E(2) levels were subnormal in 56%, 74%, and 74%, respectively, of opioid consumers. Forty-eight men (89%) exhibited subnormal levels of either FT or E(2). Either TT or E(2) level was subnormal in all 28 men consuming the equivalent of 100 mg of methadone daily and in 19 of 26 (73%) consuming smaller opioid doses. Eighty-seven percent (39 of 45) of opioid-ingesting men who reported normal erectile function before opioid use reported severe erectile dysfunction or diminished libido after beginning their opioid therapy. Commonly prescribed opioids in sustained-action dosage forms usually produce subnormal sex hormone levels, which may contribute to a diminished quality of life for many patients with painful chronic illness.

Journal Article↗

Drug delivery systems. 4. Implants in drug delivery.

In comparison with many of the other drug delivery systems, implantable pumps and implants for variable rate delivery are at a crude stage of development. Although exceptions exist, the typical implantable pump consists of an electromechanically complex mechanism to regulate drug delivery from a percutaneous refillable reservoir, while power to drive the system comes from a transcutaneous energy transmission system. The potential for electrical or mechanical failure is high, and the systems are not yet sufficiently convenient or easy to use to recommend in a routine therapy. Problems with refilling of an apparently well designed implanted reservoir have been observed while, at the same time, cutaneous energy transmission systems are not well established. In most instances, the development of an elementary osmotic pump system dosage form follows a well defined path of physical-chemical formulation and clinical testing. The benefits most often provided by the dosage form are expected to be (1) increase in selectivity of drug action achieved by the system's zero-order release rate, and (2) decrease in frequency of administration. The success in achieving these values is quantifiable from the pharmacology of the drug substance and its pharmacokinetics. Osmotic and other technical approaches to producing economical, rate-controlled dosage forms will make it possible for all new pharmaecutical products to carry kinetic specification of rate as well as static specification of content. This review considers the characteristics of the ideal implantable pump, the clinical situations which require pumps, the limitations of portable pumps, and the detailed characteristics of existing implantable pumps and implants. Most of the review, however, focuses on insulin delivery because of the importance of this subject.

Chlorofluorocarbons, Methane↗

Sublingual nitroglycerin. I. Comparative evaluation of the physical stability of commercially available tablets.

The physical stability of one type of stabilized molded and three types of compressed nitroglycerin tablets was studied. The evaporation rate of nitroglycerin was controlled by its vapour pressure and by the matrix effect of the dosage forms. The four products showed different vapour pressures and matrix effects. In time nitroglycerin escapes from the outmost layers of the tablets; the dosage form in which the drug showed the lowest vapour pressure (the stabilized molded tablet) was found to be the most stable one. However, from the time when the drug had escaped from the outmost layers of the dosage form, the matrix effect became dominant. When nitroglycerin tablets were stored in tightly closed containers at room temperature potency loss was minimal. Even when the bottles were opened regularly this did not result in a significant loss of the drug. Measures are suggested to minimize drug evaporation.

Administration, Sublingual↗

Clinical pharmacokinetics and diuretic effect of furosemide in plain tablet and retard capsule with normal subjects and cirrhotic patients.

The dissolution profiles of furosemide in various solutions were studied with plain tablet and retard capsule of furosemide. The rate constant and percent dissolution in retard capsule were lower than that in plain tablet. Clinical pharmacokinetics and diuretic effect of furosemide after oral administration of two dosage forms were also studied with 3 normal subjects and 3 cirrhotic patients. In normal subjects, the extent of furosemide absorption from retard capsule was 45% of plain tablet. The daily urine volume after oral administration of two dosage forms was comparable, however, quite different profiles were observed between these dosage forms. In patients, the extent of furosemide absorption in retard capsule was one half that of plain tablet. The dose of retard capsule was increased without adverse reactions, thus decreasing of ascites, which was not observed with plain tablet, was achieved with increasing urine volume.

Adult↗

PK-PD modelling of the effect of cefaclor on four different bacterial strains.

The effect of cefaclor against relevant bacterial strains was studied by employing a combined in vivo pharmacokinetic (PK)-in vitro pharmacodynamic (PD) approach. For this purpose selected isolates of Escherichia coli, Moraxella catarrhalis, Haemophilus influenzae and Streptococcus pneumoniae were exposed in vitro to the interstitial cefaclor profile obtained in vivo in the interstitial space fluid of human tissue after administration of commonly used doses of cefaclor and the change in the number of colony forming units per millilitre (CFU/ml) versus time was monitored. Fitting of the data using a modified E(max)-model resulted in a set of mean pharmacodynamic parameters (k0, k(max), EC50) for each bacterial strain. The parameters derived from these experiments were used in a computer-simulation of the antibacterial effects for different dosing regimens and formulations of cefaclor, notably an immediate (IR) and a modified (MR) release formulation. Dosage regimens were compared using the ratio between the number of bacteria remaining after 24 h of a given treatment (N24h). The results indicate that the number of bacteria of all investigated strains killed per day is equivalent when the same daily dose is administered twice a day with the MR dosage form than when given three times a day with the IR dosage form, in spite of the fact that the MR dosage form has approximately 20% lower bioavailability. Best results were obtained with the three-times a day regimen of the MR formulation. In conclusion, the present in vivo-PK/in vitro-PD simulations of the antimicrobial effects of cefaclor indicate that a twice-daily treatment with a MR formulation may offer a convenient and safe alternative to the conventional tid treatment.

Anti-Bacterial Agents↗

Evidence for site-specific absorption of a novel ACE inhibitor.

Moexipril [2-[(1-ethoxycarbonyl)-3-phenylpropyl]amino-1-oxopropyl]-6, 7-dimethoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (S,S,S)], an ester prodrug of an ACE inhibitor, was formulated in controlled-release preparations with a range of in vitro release rates, to provide a prolonged input of drug in vivo. However, pharmacokinetic studies with the controlled-release dosage forms in humans produced plasma profiles with the same characteristics and time to peak as an immediate-release capsule. In vitro dissolution data from the controlled-release dosage form, as well as the known characteristics of the polymer used to control drug release from the dosage form, suggest no reason to suspect an abrupt halt to the in vivo release of the drug after 1-2 hr. The lack of sustained blood levels is, therefore, most likely due to failure of the GI tract to absorb the drug beyond some location in the upper small intestine, i.e., site-specific absorption. This theory is supported by a series of computer simulations involving moexipril and the active moiety, moexipril diacid. Possible mechanisms include poor drug permeability, a pH effect whereby the zwitterionic form of the drug is more rapidly absorbed, and esterase cleavage of moexipril to the poorly absorbed moexipril diacid.

Absorption↗

Application of a radiotelemetric system to evaluate the performance of enteric coated and plain aspirin tablets.

The bioavailability of enteric coated and plain aspirin tablets was studied in four beagle dogs. Blood sampling for enteric coated tablets was planned with the aid of a radiotelemetric system. The release of aspirin from its dosage form was detected by monitoring the change in intestinal pH. Aspirin and salicylic acid levels in plasma obtained from the enteric coated dosage form exhibited familiar concentration versus time absorption profiles. Variation in the plasma concentrations of these two compounds within each dog studied (four runs each) was relatively small when time zero was adjusted to the commencement of tablet dissolution. The plasma levels obtained from plain aspirin (three runs each), however, show atypical absorption. The estimated absolute bioavailability was 0.432 +/- 0.0213 and 0.527 +/- 0.0260 for enteric coated and plain aspirin, respectively. Other pharmacokinetic parameters for these two dosage forms such as the highest observed plasma concentration (Cmax) (10.9 +/- 0.535 microgram/mL versus 13.6 +/- 1.88 micrograms/mL) and the time to reach Cmax (tmax) (26.6 +/- 1.94 min versus 31.0 +/- 7.04 min) agree well. The mean values for gastric emptying time, in vivo coating dissolution time, and in vivo disintegration/dissolution time of the tablet core for enteric coated aspirin are 48.7 +/- 7.23 min, 44.3 +/- 3.80 min, and 34.7 +/- 2.04 min, respectively.

Animals↗