Capsule Suspension Research Articles

Formation of polyelectrolyte microcapsules with chemically bound adsorbed molecules of fluorescein isotiocyanate and their destruction under laser action

Polyelectrolyte capsules with molecules of fluorescein isotiocyanate included in the shell have been obtained. The inclusion of dye molecules in the shell of the capsule allows the photosensibilized destruction of its structure. The measurements of the fluorescence intensity of a dye that was present in the shell revealed effective dissipation of the energy of photoexcited molecules by the surrounding organic matrix. The capsule suspension was irradiated by a laser in the absorption band of fluorescein isotiocyanate molecules. By measuring the size distribution of the capsules before and after irradiation with a laser it was shown that the capsules are destroyed under the effect of laser radiation.

Emulsion Drops with Complex Interfaces: Globular Versus Flexible Proteins

AbstractThis study focuses on the flow behavior of emulsion drops with complex interfaces. The experimental approach includes three different length scales: (i) interfacial rheology is discussed for adsorbed proteins with different molecular structure (compact and globular for beta‐lactoglobulin versus flexible and random coil for beta‐casein); (ii) the flow of single drops with macromolecular adsorption layers is studied using optical flow cells; (iii) dilute emulsions are investigated using rheology and rheo‐small angle light scattering (rheo‐SALS). Different hydrodynamic models for drops with and without interfacial viscoelasticity are assessed. For the case of rigid interfacial layers, a comparison with capsule suspension models suggests that drops stabilized by adsorbed particles or globular proteins behave like “soft capsules” surrounded by a jammed shell. Their behavior on the single drop level is similar to the mechanics of red blood cells or vesicles. magnified image

Dynamic rheology of a dilute suspension of elastic capsules: effect of capsule tank-treading, swinging and tumbling

Three-dimensional numerical simulations are used to study the effect of unsteady swinging and tumbling motion on the rheology of a dilute suspension of oblate-shaped elastic capsules. Unlike a suspension of initially spherical capsules undergoing the steady tank-treading motion for which the rheology is constant in time, the suspension of non-spherical capsules is time-dependent due to the unsteady capsule motion. In a simple shear flow, the non-spherical capsules undergo a transition from the tank-treading/swinging to the tumbling motion with a reduction in the shear rate or an increase in the ratio of the internal to external fluid viscosities. We find that the time-averaged rheology obtained for the non-spherical capsules undergoing the unsteady motion is qualitatively similar to that obtained for the spherical capsules undergoing the steady tank-treading motion, and that the tank-treading-to-tumbling transition has only a marginal effect. The time-averaged rheology exhibits a shear viscosity minimum when the capsules are in a swinging motion at high shear rates but not at low shear rates. This is a remarkable departure from the behaviour of a vesicle suspension which exhibits a shear viscosity minimum at the point of transition. We find that the shear viscosity in a capsule suspension can decrease as well as increase with increasing viscosity ratio during both tank-treading and tumbling motions, while that of a vesicle suspension always decreases in tank-treading motion and increases in tumbling motion. We then seek to connect the time-dependent rheology with the time-dependent membrane tension, capsule orientation, deformation and tank-treading velocity. At low shear rates, the numerical results exhibit a similar trend to that predicted by analytical theory for rigid ellipsoids undergoing tumbling motion. The trend differs during swinging motion due to the periodic deformation and time-dependent variation of the membrane stress. The elastic component of the shear stress is minimum when the capsules are maximally compressed, and is maximum when the capsules are maximally elongated. In contrast, the viscous component is related to the periodic variation of the tank-treading velocity synchronized with the swinging motion, and the rate of capsule elongation or compression. The swinging or tumbling velocity makes no contribution to the time-dependent rheology.

B112 GPUを用いたCapsuleサスペンジョンの大規模計算手法の開発(B1-3 生体流体工学1)

B112 GPUを用いたCapsuleサスペンジョンの大規模計算手法の開発(B1-3 生体流体工学1)

Pediatric Phase I Trial and Pharmacokinetic Study of Vorinostat: A Children's Oncology Group Phase I Consortium Report

The purpose of this study was to determine the maximum-tolerated dose (MTD), dose-limiting toxicities (DLT), and pharmacokinetics of vorinostat administered as a single agent and in combination 13-cis retinoic acid (13cRA) in children with refractory solid tumors; to evaluate the tolerability of the solid tumor MTD in children with refractory leukemias; and to characterize the pharmacokinetics of a vorinostat suspension in children. Vorinostat was administered orally daily starting at 180 mg/m(2)/d with escalations planned in 30% increments. Pharmacokinetic studies were performed with the initial dose. Acetyl-histone (H3) accumulation was assessed by Western blotting of peripheral blood mononuclear cells (PBMC). Sixty-four patients were enrolled on this multipart trial. In patients with solid tumors, the MTD was 230 mg/m(2)/d with dose-limiting neutropenia, thrombocytopenia, and hypokalemia at 300 mg/m(2)/d. DLTs observed with the combination of 13cRA and vorinostat included thrombocytopenia, neutropenia, anorexia, and hypertriglyceridemia, resulting in a MTD of vorinostat 180 mg/m(2)/d 4 times per week and 13cRA 80 mg/m(2)/dose twice per day, days 1 through 14 every 28 days. Wide interpatient variability was noted in vorinostat disposition, with area under the concentration-time curves at 230 mg/m(2)/d for the capsule (range, 1,415 to 9,291 ng/mL x hr) and oral suspension (range, 1,186 to 4,780 ng/mL x hr). Significant accumulation of acetylated H3 histone in PBMC was observed after administration of vorinostat, particularly at higher doses. One patient with neuroblastoma experienced a complete response to the combination. In children with recurrent solid tumors, vorinostat is well-tolerated at 230 mg/m(2)/d, with a modest dose reduction being required when combining vorinostat with 13cRA. Drug disposition is similar to that observed in adults.

Rheology of a dilute suspension of liquid-filled elastic capsules

Rheology of a dilute suspension of liquid-filled elastic capsules in linear shear flow is studied by three-dimensional numerical simulations using a front-tracking method. This study is motivated by a recent discovery that a suspension of viscous vesicles exhibits a shear viscosity minimum when the vesicles undergo an unsteady vacillating-breathing dynamics at the threshold of a transition between the tank-treading and tumbling motions. Here we consider capsules of spherical resting shape for which only a steady tank-treading motion is observed. A comprehensive analysis of the suspension rheology is presented over a broad range of viscosity ratio (ratio of internal-to-external fluid viscosity), shear rate (or, capillary number), and capsule surface-area dilatation. We find a result that the capsule suspension exhibits a shear viscosity minimum at moderate values of the viscosity ratio, and high capillary numbers, even when the capsules are in a steady tank-treading motion. It is further observed that the shear viscosity minimum exists for capsules with area-dilating membranes but not for those with nearly incompressible membranes. Nontrivial results are also observed for the normal stress differences which are shown to decrease with increasing capillary number at high viscosity ratios. Such nontrivial results neither can be predicted by the small-deformation theory nor can be explained by the capsule geometry alone. Physical mechanisms underlying these results are studied by decomposing the particle stress tensor into a contribution due to the elastic stresses in the capsule membrane and a contribution due to the viscosity differences between the internal and suspending fluids. It is shown that the elastic contribution is shear-thinning, but the viscous contribution is shear thickening. The coupling between the capsule geometry and the elastic and viscous contributions is analyzed to explain the observed trends in the bulk rheology.

The First-in-Human Study of the Hydrogen Sulfate (Hyd-Sulfate) Capsule of the MEK1/2 Inhibitor AZD6244 (ARRY-142886): A Phase I Open-Label Multicenter Trial in Patients with Advanced Cancer

In part A, the aim was to define the maximum tolerated dose (MTD) of the hydrogen sulfate (Hyd-Sulfate) oral capsule formulation of the mitogen-activated protein kinase kinase inhibitor AZD6244 (ARRY-142886). In part B, the aim was to compare the pharmacokinetic profile of the new Hyd-Sulfate capsule with the initial AZD6244 free-base suspension and further characterize the pharmacodynamic profile and efficacy of the new formulation. In part A, 30 patients received escalating doses of AZD6244 Hyd-Sulfate twice daily. In part B, 29 patients were randomized to a single dose of the Hyd-Sulfate capsule or free-base suspension, followed by a washout, then a single dose of the alternative formulation. Patients received the Hyd-Sulfate capsule twice daily at MTD of part A thereafter. The MTD of the Hyd-Sulfate capsule was 75 mg twice daily. Dose limiting toxicities were Common Terminology Criteria for Adverse Events grade 3 acneiform rash and pleural effusion. Fatigue (65.7%) and acneiform dermatitis (60.0%) were the most frequent adverse events at the MTD. Based on area under curve(0-24), exposure of the 75 mg Hyd-Sulfate capsule relative to the 100 mg free-base suspension was 197% (90% confidence interval, 161-242%). Pharmacodynamic analysis showed that inhibition of 12-O-tetradecanoylphorbol-13-acetate-induced extracellular signal-regulated kinase phosphorylation in peripheral blood lymphocytes was related to plasma concentrations of AZD6244, with an estimated IC(50) of 352 ng/mL and maximum inhibition (E(max)) of approximately 91%, showing target inhibition. A patient with metastatic melanoma bearing a V600E BRAF mutation achieved a complete response persisting after 15 months of therapy. The AZD6244 Hyd-Sulfate capsule formulation has shown a favorable toxicity, pharmacokinetic, and pharmacodynamic profile, and is being taken forward in ongoing clinical trials.

Formation and destruction of polyelectrolyte microcapsules modified by rhodamine 6G

Polyelectrolyte capsules with Rhodamine 6G molecules included into the shell are obtained in this work. The inclusion of dye molecules into the shell can provide the destruction of capsules by photosensitization. Measurements of the dye fluorescence intensity in the shell show that the energy of photoexcited molecules is effectively dissipated by the surrounding organic matrix. The capsule suspension is laser irradiated in the absorption band of Rhodamine 6G molecules. Measurements of the size distribution of capsules before and after laser irradiation reveal that the capsules are destroyed by laser illumination.

Preliminary examination of integrated vector management in a tropical rainforest area of Cameroon

In the tropical rainforest area of Cameroon, people are affected by blackflies (Simulium spp.) and mosquitoes (Anopheles spp). Use of insecticide-treated bed nets (ITNs) has been promoted to protect vulnerable groups from mosquito bites, whereas historically indoor residual spraying (IRS) was the primary intervention. In a malaria-endemic area, a pilot study examined different mosquito control interventions applied to entire villages to assess their impact on vectors, malaria incidence and the quality of life of the communities. The Sanaga River near these villages was treated with insecticide to kill blackfly larvae. A medical survey of the six villages had shown that 20% of the population suffered from malaria, while 50% were infected with onchocerciasis and 5% with Loa loa. IRS+ITN using ICON CS (lambda-cyhalothrin capsule suspension formulation) or improved screening of houses combined with outdoor misting reduced the numbers of mosquitoes collected from exit traps compared to the other treatments. More sporozoites were detected in mosquitoes sampled in exit traps in the untreated village than in the treated villages. Malaria incidence several months after treatments was not significantly different from pre-treatment levels. Blackfly adult populations were reduced for several weeks following larvicide application but recovered when treatment was halted.

Pendimethalin Applications in Stale Seedbed Rice Production

Field studies were conducted from 2005 through 2007 to determine the response of three rice cultivars (‘Cocodrie’, ‘Wells’, and ‘Lemont’) to three application timings and two formulations of pendimethalin in a stale seedbed rice production system. Pendimethalin formulated as an emulsifiable concentrate and capsule suspension was applied to rice 0, 3, and 7 d after planting. No visual injury was detected for any cultivar. Seedling density, days to 50% heading, and rice yield were not affected by pendimethalin formulation or application timing. The practice of planting cultivars with excellent seedling vigor into nondisturbed soils with greater available moisture could provide an opportunity to use pendimethalin as a preemergence herbicide for rice production.

Fexofenadine hydrochloride in the treatment of allergic disease: a review

Fexofenadine is a selective, non-sedating H1 receptor antagonist, marketed in the United States since 2000. The FDA approved an oral suspension in 2006, for the treatment of seasonal allergic rhinitis and chronic idiopathic urticaria in children. The tablet, capsule, and oral suspension are bioequivalent. Although fexofenadine does not use P450 CYP 3A4 it does interact with a number of drugs at P-glycoprotein and organic anion transporter polypeptides. The risk of toxicity from other drugs may increase with the administration of fexofenadine. Orange and grapefruit juices reduce the bioavailability of fexofenadine. Fexofenadine has been shown to have an impact on inflammatory mediators, other than histamine, such as decreasing the production of LTC(4), LTD(4), LTE(4), PGE(2), and PGF(2α); inhibiting cyclo-oxygenase 2, thromboxane; limiting iNOS generation of NO; decreasing cytokine levels (ICAM-1, ELAM-1, VCAM-1, RANTES, I-TAC, MDC, TARC, MMP-2, MMP-9, tryptase); and diminishing eosinophil adherence, chemotaxis, and opsonization of particles. These effects may provide benefit to some of the inflammatory responses of an acute allergic reaction and provide a basis for future development of H1 antagonists with stronger anti-inflammatory effects. These studies also support the contention that fexofenadine is effective for the treatment of allergic rhinits and chronic idiopathic urticaria.

Identification and dosimetric features of γ-irradiated cefadroxil by electron spin resonance

In the present work, electron spin resonance (ESR) identification of γ-irradiated cefadroxil monohydrate (CM), duricef capsule (DC) and duricef suspension (DS) and their potential use as normal and/or accidental dosimetric materials were investigated in the dose range of 1–25 kGy. Although unirradiated samples did not exhibit any ESR signals, irradiated samples were observed to present ESR spectra with many resonance lines originating from radiation induced radical or radicals. Dose-response curves associated with the resonance peak heights of CM ( I 1, I 2) and DS ( I 3, I 4, I 5, I 6) were found to follow linear and power functions of applied radiation dose, respectively. Simulation calculations were performed to determine the structure and spectral parameters of the radiation-induced radicalic species involved in the formation of experimental ESR spectrum of CM using, as input, the room temperature signal intensity data obtained for a sample irradiated at dose of 10 kGy. Kinetic behaviors and activation energies of the radicalic species were also calculated using the data obtained from annealing studies performed at five different temperatures. The presence of detectable signal intensities even after a storage period of 100 days was considered as providing an opportunity in the discrimination of irradiated CM and DS from unirradiated ones. Basing on room temperature signal intensity decay and dose–response data, it was concluded that CM and DS present the features of a good dosimetric material.

Microencapsulated Clomazone: Formulation Stability, Tank Mix Volatility, and Solvent Effects

Abstract Clomazone is microencapsulated and sold in the U.S. as a dispersion in water, a capsule suspension (CS), under the name Command®®Command is a trademark of FMC Corporation. 3ME herbicide. Our encapsulated formulation reduces the volatility of the active ingredient when it is applied to the soil surface in a typical agricultural spray use. The commercialized formulation was selected from among hundreds of encapsulated formulations for its ability to reliably control volatility. Many of the rejected formulations did not control volatility, and it was only through a careful optimization of the encapsulation process that we came to our selection. As part of our formulation development process, we developed a laboratory volatility assessment method for use in screening formulations. This method determined the volatility following a soil application and normalized the volatility of the encapsulated formulations to that of the older Command 4EC herbicide formulation. Our optimized formulation was introduced to the market in 1996 to control volatility. A sample of the first production batch of commercial clomazone 3CS formulation, which had been stored at room temperature and regularly assessed for ten years, continues to provide excellent control of volatility. This indicates that the capsules have remained intact and functional, and that the proportion of clomazone in the capsule, versus outside, has not changed as the formulation aged. When these capsules are diluted in water, some clomazone slowly diffuses out of the capsules. This release is limited by the water solubility of clomazone. Even for excessive residence times in the spray tank, the volatility from the soil surface increased only slightly and was well within the acceptable range, for dilutions used for agricultural spray application. Improper addition of solvents and surfactants to the formulation can provide a phase where the clomazone is soluble, and this solubility will extract clomazone from the capsules. Under these conditions the volatility of the product increased so that it was similar to an unencapsulated formulation. In contrast, addition of other herbicides or spray additives to the spray tank mix had little impact on the volatility.

Note: Evaluating insecticides for the control of overwintered adults ofEurygaster integriceps under field conditions in Turkey

The Sunn pest Eurygaster integriceps Puton is the most harmful pest of cereals in Turkey and the surrounding countries. Chemical control has been employed against the nymph stages of the pest. The efcac y of six products [acetamiprid (SL, soluble concentrate), chlorpyrifosethyl (EC, emulsiable concentrate), lambda-cyhalothrin (CS, capsule suspension), monocrotophos (SC, suspension concentrate), thiacloprid (SC) and zeta-cypermethrin (EC)] was tested on overwintered adults of E. integriceps, with applications to wheat at the shooting stage. In a study conducted at Siverek, S ‚ anlurf a in the southeastern Anatolia Region, the most effective insecticide was found to be lambda-cyhalothrin. It gave very promising results in controlling the pest and reduced subsequent egg laying and the appearance of nymphs in the trial area. The results showed that chemical control of overwintered adults of the Sunn pest in early spring is possible with lambda-cyhalothrin.

Fall and Early Preplant Application Timing Effects on Persistence and Efficacy of Acetamide Herbicides1

The persistence and efficacy of acetamide herbicides at application timings from fall to preemergence (PRE) were studied in 1998 and 1999 on mollisols (1.1 to 2.8% organic carbon). Metolachlor, s-metolachlor, acetochlor (as an emulsifiable concentrate [EC] formulation and two encapsulated formulations, capsule suspension [CS] and microencapsulated [ME]), and the combination of flufenacet metribuzin were evaluated at five application times including late fall, 60 and 30 d early preplant (EPP), preplant incorporated, and PRE. Soil bioassays 180 d after application indicated flufenacet metribuzin, metolachlor, s-metolachlor, and the acetochlor CS had 62 to 74% giant foxtail control, whereas acetochlor EC and ME had 43 to 46% control. Applications at 60 EPP of metolachlor, s-metolachlor, and acetochlor CS provided 70 to 75% giant foxtail control in greenhouse bioassays, whereas flufenacet metribuzin, acetochlor ME, and acetochlor EC provided 38 to 57% control. At the 30 EPP timing, metolachlor and acetochlor CS had 80 to 82% control, whereas acetochlor EC provided 46% control, and acetochlor ME, flufenacet metribuzin, and s-metolachlor had 65 to 74% control. Quantitative soil analysis (0 to 6 cm) 10 d after planting (DAP) indicated metolachlor, s-metolachlor, and acetochlor CS concentrations ranged from 12 to 16% and 32 to 47% of applied herbicide for the fall and PRE application timings, respectively, whereas acetochlor (ME and EC) were from 1 to 3% and 16 to 21% of applied for the fall and PRE application timings, respectively. Bioassay reduction was correlated (R2 = 0.68) with soil-herbicide concentrations at 10 DAP.Nomenclature: Acetochlor; flufenacet; metolachlor; metribuzin; s-metolachlor; giant foxtail, Setaria faberi Herrm. #3 SETFA.Additional index words: Soil dissipation.Abbreviations: CS, capsule suspension; DAP, days after planting; EC, emulsifiable concentrate; EPP, early preplant; ME, microencapsulated; OC, organic carbon; PPI, preplant incorporated; PRE, preemergence; SETFA, giant foxtail.

Development, manufacture and application of Beta-Cypermethrin aqueous capsule suspension

The optimal formula of Beta-Cypermethrin aqueous capsule suspension was screened out through the experiment, preparation and manufacture of basic formulas, which has no sedimentation, suspended drops of oil, peels and agglomerating and the diameter of capsule is in range of 10–30 μm, conformed to the technical requirement. The aftereffect of the 3.3% Beta-Cypermethrin aqueous capsule suspension which was manufactured according to the optimal formula was up more than 25 days. The experiments on controlling the larvae ofDendrolinmus superans Butler and the adults ofXylotrechus rusticus L were carried out with different concentrations of this chemical. The death rate reached 80% when 250 times solution of the chemical was sprayed on stem to control the larvae ofD. superans. For control of the adults ofX. rusticus, 200, 400 and 600 times solution of the chemical were applied and their control effects (death rate) reached 85.23%, 74.21% and 66.59% respectively. Two kinds of solution (200 times and 300 times) of the chemical were used to control the larvae ofD. superans in large area, and the control effect for both concentrations was over 90%.

Wash resistance of insecticide-treated materials

The effectiveness of insecticide-treated materials (ITMs) for malaria control is reduced by washing them. This research in Colombia and Bolivia investigated the resistance of different insecticide formulations and, in particular, a commercially available impregnated bednet (PermaNet ®) which provides chemical protection for the insecticide. The fabrics studied were all polyester; the pyrethroids used for impregnation were deltamethrin (tablet and suspension concentrate both at 25 mg/m 2 target dose), lambdacyhalothrin (capsule suspension at 15 mg/m 2; laboratory study only), alphacypermethrin (suspension concentrate at 40 mg/m 2) and, in the case of PermaNet, deltamethrin (55 mg/m 2). The indicator of wash resistance was Anopheles spp. mortality (using the bioassay cone method) before and after different numbers and intensities of washing. When the fabrics were washed under controlled conditions, gently with water and a bar of soap, the wash resistance of all formulations was good (100% Anopheles mortality after 3 washes). However, when the impregnated nets were soaked for 30–60 min and washed with soap powder and tap water by local women in the usual way, the mortality after 4 washes declined considerably (43.5% and 41.3% for deltamethrin tablets and liquid respectively when washing every second day). Alphacypermethrin showed slightly better results after 3 washes every 7th day compared to deltamethrin tablets (63.8% and 43.3% mortality, respectively). The wash resistance offered by PermaNet was much better and longer lasting: Anopheles mortality after 4 washes was 92.6%, after 10 washes 83.7% and after 20 washes 87.1%. The limitations of commercially available wash-resistant nets are, however, their limited accessibility and the difficulty of replacing all existing bednets with a new product.

Bio-efficacy of herbicides applied in cumin (Cuminum cyminum) and their carry- over effects on succeeding pearlmillet (Pennisetum glaucum)

A field experiment was conducted during the winter seasons of 201011 and 201112 to study bio-efficacy of pendimethalin available in capsule suspension form (CS) and other recommended herbicides on the productivity of cumin ( Cuminum cyminum L.) and their carry-over effects on the succeeding pearlmillet [ Pennisetum glaucum (L) R. Br . Emend. Stuntz.]. Pre-emergence application of pendimethalin CS @ 484 g/ha + 1 hand-weeding con- trolled the weeds effectively in cumin and resulted in seed yield of 684 kg/ha, which was at par with weed-free check (701 kg/ha). Increase in the dose of pendimethalin CS from 484 to 580 and 580 to 677 g/ha did not influ- ence seed yield of cumin but significantly suppressed plant count and biomass of succeeding pearlmillet. Applica- tion of pendimethalin liquid formulation @ 750 g/ha exhibited similar trend. Oxadiargyl and oxyfluorfen applied @ 50 g/ha + 1 hand-weeding at 30 days decreases the weed stand and weed dry matter, where the extent of control was at par with weed-free plots without any residual effect on succeeding pearlmillet. Post-emergence application of oxadiargyl @ 50 g/ha + 1 hand-weeding at 30 days recorded maximum seed yield (715 kg/ha), net return ( 58,400/ha) and benefit: cost ratio (4.08), with weed control efficiency of 99%, closely followed by oxyfluorfen 50 g/ha + 1 hand-weeding.

Regular Foams, Loaded Foams and Capsule Suspension in the Foam for Hohlraums in ICF

Many target designs for laser- and ion-driven ICF include foam parts for direct and indirect targets to be investigated in continuing plasma experiments. The freestanding soft foams are described here for comparative plasma experiments. They are pure foam, foam loaded with fine metal dopants or with nanoscale metal seeds. The foams produced and studied have similar fine and regular structure, densities around critical for the third harmonics of Nd-laser and are appropriate for use inside hohlraums. A technique was developed to fill cylinders with such low-density foams and to suspend symmetrically hollow capsules inside.

The efficacy of various pyrethroid insecticides for use on odour-baited targets to control tsetse.

The efficacy of various pyrethroid insecticides for use on odour-baited targets to control tsetse was compared in Zimbabwe. Formulations were applied to cotton cloth and polyester net and, at various intervals, the materials were bioassayed by exposing fed female Glossina pallidipes (Austen) (Diptera: Glossinidae) to cloth for 45 s or by inducing them to collide briefly with net. Trial formulations were compared with deltamethrin suspension concentrate (s.c.), the insecticide currently used in tsetse control operations in Zimbabwe. Applying 0.8% suspension of alphacypermethrin to cloth or net produced high mortalities for 9 months which was similar in performance to 0.4% suspension of deltamethrin s.c. Deltamethrin s.c. and beta-cyfluthrin s.c. applied to cloth as 0.1% suspensions were equally effective, producing high mortalities for 2 months during the wet season, and 0.8% suspension of beta-cyfluthrin was effective for 12 months. Suspensions of 0.1% lambdacyhalothrin capsule suspension or 0.1% lambdacyhalothrin wettable powder were significantly less effective than 0.1% deltamethrin s.c. Chemical analyses showed that increasing the concentration of insecticide applied to material increased the initial amount of insecticide on the material and decreased the subsequent rate of loss; 0.1% suspension of beta-cyfluthrin s.c. applied to cloth produced an initial concentration of approximately 280 mg/m2 which declined by 94% in 12 months whereas 0.8% suspension showed no significant decrease in concentration (mean= 1304 mg/m2) over the same period. For controlling tsetse by means of pyrethroid-treated targets, it is suggested that beta-cyfluthrin s.c. is as effective as deltamethrin s.c. but that alphacypermethrin s.c. should be used at twice the concentration of deltamethrin s.c. to obtain the same performance.