Wolman's disease--a case report

Wolman's disease is a rare autosomal recessive lysosomal storage disorder. We report a case, which we identified with foamy histiocytes in bone marrow and adrenal calcification in radiological imaging. The diagnosis can be made on minimal investigation when clinically suspected. But cytogenetic study is required to substantiate the diagnosis further.

Bioequivalence study of rifampicin in fixed-dose combination of rifampicin and isoniazid vs. separate formulations

The benefits of fixed-dose combinations of antituberculosis agents are well recognized by the World Health Organization (WHO) and International Union Against Tuberculosis and Lung Disease (IUATLD) and preferred over separate formulations. Therefore, a comparative bioequivalence study of rifampicin and isoniazid together in a fixed-dose combination and separately (at the same dose levels) was performed on a group of 12 healthy subjects. The study was designed as a single-blind, crossover experiment. Nine blood samples were collected from each subject over a period of 24 h. The plasma concentrations of rifampicin were assessed by a method developed in this laboratory. Various pharmacokinetic parameters of rifampicin such as AUC, Cmax, Tmax and t1/2 were also calculated. The study demonstrates that a fixed-dose combination (test formulation) and separate formulations (standard formulations) are bioequivalent for rifampicin.

The WHO simplified study protocol in practice: investigation of combined formulations supplied by the WHO

SETTING

The benefits of fixed-dose combination (FDC) formulations of rifampicin, isoniazid and pyrazinamide over individual formulations are well recognised.

OBJECTIVES

To evaluate the comparative bioavailability of antituberculosis drugs in FDC formulations and the same doses in separate formulations of antituberculosis drugs, using a simplified protocol developed by the World Health Organization (WHO).

METHODS

Twenty healthy volunteers were included in the study and evaluated for bioequivalence of rifampicin in a cross-over experimental design. After administration of drugs the plasma concentration of rifampicin and desacetyl-rifampicin was measured repeatedly up to 8 hours in both plasma and urine. Various pharmacokinetic parameters of rifampicin, such as Cmax, Tmax, elimination rate constant, area under the curve (AUC) up to 8 hours and absorption efficiency were calculated.

RESULTS

No significant differences were observed between the FDCs and separate formulations when Cmax, Tmax, AUC and absorption efficiencies were compared by parametric test and Hauschke's analysis.

CONCLUSION

The WHO simplified protocol is suitable for evaluating bioequivalence of antituberculosis drugs.

Localized paclitaxel delivery

While the search for new antineoplastic agents is in progress, optimization of delivery for existing drugs will remarkably improve the current scenario in the management of cancer. Paclitaxel, a new antineoplastic agent, is one such drug deserving attention in the field of regional drug delivery, offering immense pharmacokinetic as well as therapeutic advantage via localized delivery. The antiangiogenic activity of paclitaxel has been demonstrated using the chick chorioallantoic membrane model (CAM). This review focuses on the antiangiogenic activity of paclitaxel supported by the evidence that angiogenesis inhibitors display potential synergism with cytotoxic agents in the treatment of primary and metastatic cancers. Preclinical trials have confirmed that the biological and cytotoxic effects of paclitaxel on several tumor cell lines are enhanced by the increase in both the drug concentration and the duration of exposure. Sufficient experimental evidence has accumulated to state that localized delivery will exploit the multiple pharmacological effects of paclitaxel in the treatment of refractory and metastatic cancerous diseases. The drug delivery systems, namely, microspheres, surgical pastes and implants, fabricated for localized paclitaxel delivery are reviewed explaining the concept of increased tumor burden alleviating body burden as a consequence of such delivery systems. Some of the preclinical trials are very encouraging and speculate a promising future for these devices in the battle against solid tumors. Finally, the review briefs on the possibilities for better paclitaxel delivery and the future drug delivery systems for localized cancer chemotherapy.

Transdermal iontophoresis. Part II: Peptide and protein delivery

The advent of sophisticated biotechnological processes has generated an interest in peptide and protein pharmaceuticals. However, the rapid developments in biotechnology are not matched by the developments in the delivery of these molecules. Presently, most of the peptides and proteins are delivered by parenteral route due to their poor oral bioavailability. The inherent discomforts associated with the parenteral therapy has prompted investigations into other nonparenteral routes and drug delivery techniques. Transdermal iontophoresis is one such technique showing good promise in the controlled and enhanced delivery of peptides and proteins. It offers noninvasive, continuous, pulsatile delivery as well as preprogramed complex dosing regimens. Miniature battery powered and wearable patches for peptides and proteins are expected to be on the market by the turn of this century. In continuation of our earlier review, this review explores the potential of transdermal iontophoresis for the delivery of peptides and proteins with the main focus on the suitability of the technique along with the factors to be considered in the design of this drug delivery system and its future prospects.

Extrusion and spheronization in the development of oral controlled-release dosage forms

The concept of multiparticulate dosage forms was introduced in the 1950s. With the increasing use of multiparticulate controlled release (CR) oral dosage forms, in recent times there has been a rise in interest in the methods of preparing these dosage forms. A method that has gained increased usage over the past few years is that of extrusion and spheronization. It has been extensively explored as a potential technique and also as a future method of choice for preparation of multiparticulate CR dosage forms. In this review an attempt is made to outline the general process of extrusion and spheronization and to assess its importance in the development of multiparticulate CR oral dosage forms.

Transdermal iontophoresis. Part I: Basic principles and considerations

The skin has increasingly become a route for the delivery of drugs with a range of compounds being considered for transdermal delivery generating a great deal of interest in this area of research. The passive delivery of most compounds across the skin is limited due to the barrier properties afforded by stratum corneum, the outermost layer of the skin. Transdermal iontophoresis is an effective technique for physically facilitating the transport of permeants across the skin by using electromotive force. It is being extensively explored as a potential means for delivery of hydrophilic, large and charged molecules and is also believed to be a future method of choice for peptides and proteins. In this context, this review focuses mainly on the basic principles and considerations of transdermal iontophoresis with particular emphasis on modeling, devices and parameters influencing transdermal iontophoresis.

Transdermal delivery of naloxone: ex vivo permeation studies

The purpose of this investigation was to study the feasibility of transdermal drug delivery of the potent opioid antagonist naloxone. The pharmacokinetic profile of naloxone makes it a suitable candidate for transdermal delivery. Ex vivo permeation of naloxone through excised rat skin was studied using a diffusion cell. Radiochemical assay of drug concentration and the use of rat as an animal model were adopted in this study. Naloxone possesses characteristics favorable to percutaneous absorption: i.e. a low molecular weight (327.37), water solubility and a good lipid-water partition coefficient of 12.94+/-1.29 at pH 7.4. The flux (microg/cm2/h) values varied from 6.59+/-0.72 in control to 27. 18+/-4.26 in dimethyl formamide. The affinity of naloxone to skin in the presence of propylene glycol was decreased by 6.2 times compared to the control. Fourier transform infrared spectroscopy was used to study the effect of various sorption promoters on intercellular lipid pathways in skin. A change in lipid fluidization corresponding to broadening for both C-H symmetric (near 2850 cm-1) and C-H asymmetric (near 2920 cm-1) stretching was observed. An attempt was made to correlate the molecular weight of sorption promoters with skin affinity values of naloxone.

Determination of rifampicin and its main metabolite in plasma and urine in presence of pyrazinamide and isoniazid by HPLC method

A reversed phase HPLC method is described for the simultaneous estimation of rifampicin and its major metabolite desacetyl rifampicin, in the presence of isoniazid and pyrazinamide, in human plasma and urine. The assay involves simple liquid extraction of drug, metabolite and internal standard (rifapentine) from biological specimens and their subsequent separation on a C18 reversed phase column and single wavelength UV detection. In plasma as well as in urine samples, all the three compounds of interest eluted within 17 min. Using methanol-sodium phosphate buffer (pH 5.2; 0.01 M) (65:35, v/v) as mobile phase under isocratic conditions, it was established that isoniazid, pyrazinamide and ascorbic acid (added to prevent oxidative degradation of analytes) did not interfere with the analyte peaks. Recoveries (extraction efficiency) for drug were greater than 90% in both plasma and urine, whereas for metabolite the values were found to be 79 and 86% in plasma and urine, respectively. The plasma and urine methods were precise (total coefficient of variation ranged from 5 to 23%) and accurate (-7 to 5% of the nominal values) for both the analytes. Individual variance components, their estimates and their contribution to the total variance were also determined. Using the same method, unknown samples supplied by WHO were assayed and good correlations were obtained between the found and intended values. The method developed proved to be suitable for simultaneous estimation of rifampicin and desacetyl rifampicin in plasma and urine samples.

Animal models for transdermal drug delivery

The purpose of this investigation was to compare the permeation characteristics of two different compounds (extremely polar and nonpolar), i.e., tritium-labeled water (W) and 14C-labeled 7-hydroxycoumarin (7-OHC), among 16 different species, including human skin. Snake skin exhibited highest permeability for both W and 7-OHC. Permeability and lag time values of W and 7-OHC across Brattleboro rat and hairless guinea pig are very close to human skin. Skin thickness in micrometers (full thickness, epidermis and stratum corneum, and stratum corneum), and number of hair follicles present in each cm2 were determined for each species. There was no relationship between number of hair follicles and permeability values for both W and 7-OHC. The skin thickness (full) was related to the relative permeability values of W, whereas for 7-OHC it was not.

Monoclonal antibodies in drug targeting

The objective of drug targeting is to deliver drugs to a specific site of action through a carrier system. In cancer chemotherapy, cytotoxic drugs kill cancerous cells but also damage normal cells. Monoclonal antibodies generated against specific antigens, when conjugated to cytotoxic drugs, can selectively deliver drugs to cancer cells while minimizing damage to normal cells. Of all the carrier systems available, monoclonal antibodies are gaining importance because of their high specificity. The purpose of this review is to provide a comprehensive account of the use of monoclonal antibodies in drug targeting, highlighting their scope and limitations.

Development and evaluation of an intracutaneous depot formulation of corticosteroids using Transcutol as a cosolvent: in-vitro, ex-vivo and in-vivo rat studies

A topical delivery system has been developed using 50% Transcutol (diethylene glycol monoethyl ether) to decrease the body burden of topically administered dexamethasone and hydrocortisone. The delivery system was evaluated in-vitro using a dissolution apparatus to measure the release of steroid from the gel. In 10 h, 29.6 +/- 0.39% dexamethasone and 45.5 +/- 0.84% hydrocortisone was released from the formulation compared with 23.0 +/- 0.48 and 39.9 +/- 0.77%, respectively, from control formulations without Transcutol. Ex-vivo evaluation was made using rat whole skin in a diffusion cell; the amount of steroid reaching the acceptor cell was significantly less from the formulation containing Transcutol compared with controls. There was also a 2-fold increase in the retention of dexamethasone and a 3-fold increase in the retention of hydrocortisone in the skin at the end of the permeation experiments compared with control experiments. In-vivo studies were made using a formulation containing [3H]hydrocortisone applied to rat skin, followed by measurement of total radioactivity in the blood. For the Transcutol formulation the area under the blood concentration-time curve (0-96 h) was 6.06 +/- 1.27 compared with 2.52 +/- 0.43 x 10(6) d min-1 mL-1 h for the control formulation, indicating a 58% reduction in body burden.