Sustained Release Devices Research Articles

MicroWick-delivered transtympanic gentamicin: Hearing effects

Problem: Transtympanic gentamicin administration has become a popular modality for the treatment of Ménière’s disease. This modality and other inner ear medical therapies are gaining increased clinical and scientific attention. We have previously described the kinetics and effects of gentamicin uptake into the inner ear after delivering the medicine into the middle ear using a variety of different techniques and sustained release modalities. In this study we focus on a newer sustained release device, the Silverstein MicroWick (Micromedical, Inc, Minneapolis, MN). Methods: We studied the effects of a single administration of gentamicin onto the microwick after implanting the wick into the round window membrane of Chinchilla laniger. One mg of gentamicin (10 mg/mL) was applied to a microwick after securing the wick in the round window niche of Chinchilla laniger. Hearing was measured before placing the wick and at the preset time points after. Results: All of the animals had normal preoperative hearing and there was no hearing loss demonstrated in the 4-hour time group. However, 40% of the animals in the 8-, 24-, and 48-hour time points exhibited a hearing loss. Conclusion: Despite the very low dose of gentamicin, we demonstrated more hearing loss at earlier time points than in previous experiments. The fact that 40% of animals demonstrated hearing loss at each time point suggests to us that the damage from gentamicin, delivered in this manner (a single low dose on a microwick), occurs early and those animals remain impaired for at least 48 hours. Meanwhile, animals whose hearing is intact for the first 8 hours likely do not suffer damage after that point. Significance: The information gained from this study and the follow-on studies will increase our scientific understanding about the effects of gentamicin on the inner ear and allow clinicians to more effectively treat patients with inner ear disorders. Support: None reported.

A simple sustained release device for the ethylene binding inhibitor 1-methylcyclopropene

The efficacy of 1-methylcyclopropene (1-MCP) gas to prevent the adverse effects of ethylene is limited by its short-term residual activity in some plants. Development of a simple 1-MCP sustained release device that prolongs 1-MCP exposure is reported herein. Sustained release devices comprised of polyvinylchloride tubes containing 0.1 g SmartFresh™ powder (a.i. 3.3% 1-MCP) and 1.25 ml deionised water were used to release 1-MCP into fibreboard cartons containing cut Geraldton waxflower (Chamelaucium uncinatum Schauer) cv. CWA Pink bunches during export shipment by air (107 h) from Australia to the UK. The devices protected flowers against abscission induced by subsequent test exposures to ethylene (10 μl l−1, 12 h, 20 °C) for 3–5 days after arrival. In contrast, pre-shipment treatments with either a single application of 790 nl l−1 1-MCP for 14 h at 2 °C or a 0.2 mM Ag+ (as silver thiosulphate; STS) pulse for 14 h at 2 °C protected flowers against exogenous ethylene for only 1–2 days of post-export life. However, pre-shipment 1-MCP fumigation was up to about three-fold more effective than either sustained 1-MCP release or pre-shipment STS treatments in reducing floral organ and leaf abscission from bunches during export. Thus, it is suggested that a combination of pre-shipment 1-MCP fumigation before export with sustained 1-MCP release during shipment should maximise efficacy against ethylene-induced waxflower flower abscission.

Corticosteroids in posterior segment disease: an update on new delivery systems and new indications.

Corticosteroids are traditionally used for inflammatory disorders because of their ability to diminish neutrophil transmigration, limit access to sites of inflammation, and decrease cytokine production. More recently, however, investigators have focused on the angiostatic and antipermeability properties of corticosteroids for posterior segment diseases such as age-related macular degeneration (AMD), diabetic retinopathy, and macular edema. Both new angiostatic and traditional corticosteroids are currently undergoing evaluation as new delivery techniques such as intravitreal injection and intraocular sustained-release devices facilitate high local angiostatic and antipermeability concentrations while minimizing extraocular toxicity. The purpose of this review is to discuss recent work concerning both the mechanism and effectiveness of these newer treatments. Steroids may exert a beneficial effect in AMD-related choroidal neovascular membranes (CNVM) through inhibition of CNVM-promoting macrophages and direct inhibition of angiogenic growth factors. They may also alter extracellular matrix turnover and inhibit matrix metalloproteinases involved in CNVM formation. Intravitreal steroid injections potently inhibit experimental CNVM in primates and rats and have shown promise in some early human pilot trials. In proliferative diabetic retinopathy, steroids may directly inhibit growth factors such as vascular endothelial derived growth factor and inhibit leukocytes that play an important role in early microvascular alterations. Intravitreal steroid injections inhibit experimental preretinal neovascularization in pigs and rats, and rubeosis in some early human studies. In addition, the effect of steroids on vascular permeability has led to their use for macular edema from many causes such as diabetes and venous occlusive disease. The use of steroids to treat a number of retinal diseases is gaining wide spread acceptance. The apparent short-term success must be balanced by the fact that the long-term safety and efficacy have yet to be determined for any of these approaches. A number of large randomized prospective clinical trials of steroid compounds and new delivery systems are currently under way for AMD, diabetic retinopathy, uveitis, and other retinovascular diseases, and hopefully these studies will provide guidance about the use of these new modalities.

A simple sustained release device for the ethylene binding inhibitor 1-methylcyclopropene

The efficacy of 1-methylcyclopropene (1-MCP) gas to prevent the adverse effects of ethylene is limited by its short-term residual activity in some plants. Development of a simple 1-MCP sustained release device that prolongs 1-MCP exposure is reported herein. Sustained release devices comprised of polyvinylchloride tubes containing 0.1 g SmartFresh(TM) powder (a.i. 3.3% 1-MCP) and 1.25 ml deionised water were used to release 1-MCP into fibreboard cartons containing cut Geraldton waxflower (Chamelaucium uncinatum Schauer) cv. CWA Pink bunches during export shipment by air (107 h) from Australia to the UK. The devices protected flowers against abscission induced by subsequent test exposures to ethylene (1011,mul l(-1), 12 h, 20 degreesC) for 3-5 days after arrival. In contrast, pre-shipment treatments with either a single application of 790 nl l(-1) 1-MCP for 14 h at 2 degreesC or a 0.2 mM Ag+ (as silver thiosulphate; STS) pulse for 14 h at 2 degreesC protected flowers against exogenous ethylene for only 1-2 days of post-export life. However, pre-shipment 1-MCP fumigation was up to about three-fold more effective than either sustained 1-MCP release or pre-shipment STS treatments in reducing floral organ and leaf abscission from bunches during export. Thus, it is suggested that a combination of pre-shipment 1-MCP fumigation before export with sustained 1-MCP release during shipment should maximise efficacy against ethylene-induced waxflower flower abscission. (C) 2004 Elsevier B. V. All rights reserved.

Patents

High-strength asymmetric cellulose membranes Membrane for the treatment of waste lubricants Cross-linked polymer blend membrane Ceramic membrane Gas chromatograph calibration Sugar preparation Crosslinked sulphonated polyimide films Graft copolymer membranes Water supply system Hydrophilic polymers Ion-conducting membrane Polymerization reactors Water purification cartridge Self-contained water filter with zeolites Multiple-well sequencing plate Semi-permeable composite membrane Membrane body Down-hole gas separation system Microfabricated nanopore device for sustained release of therapeutics Apparatus and method for cleaning membrane filtration modules

Effect of vancomycin on Staphylococcus epidermidis adherence to poly(methyl methacrylate) intraocular lenses

Purpose: To study the adherence of Staphylococcus epidermidis in variable loads (10 8 cfu/mL and 10 3 cfu/mL) to poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) and to evaluate the effect of vancomycin treatment on S epidermidis adherence to the IOL. Setting: L.V. Prasad Eye Institute, Hyderabad, India. Methods: The study was designed in 2 parts. Phase I: Twelve PMMA IOLs were soaked in a solution of S epidermidis, randomized to 10 8 cfu/mL or 10 3 cfu/mL. They were rinsed or rinsed and vortexed and cultured. Phase II: Twelve IOLs were treated with vancomycin (10 mg/mL), randomized to before and after treatment with S epidermidis. Results: Staphylococcus epidermidis adhered to all portions of the IOL with 10 8 cfu/mL and 10 3 cfu/mL bacterial loads. Treatment with vancomycin reduced S epidermidis adherence. Conclusion: Pretreatment of an IOL with vancomycin or a suitable antibiotic agent appears to reduce bacterial adherence to the IOL. Placement of a sustained-release device that could release an antibiotic agent over a specific period, reducing the incidence of postcataract endophthalmitis, should be studied.

Ethyl Cellulose and Polyethylene Glycol-Based Sustained-Release Sparfloxacin Chip: An Alternative Therapy for Advanced Periodontitis

ABSTRACTThis study reports the development of a sustained-release system of sparfloxacin for use in the treatment of periodontal disease. A sustained-release sparfloxacin device was formulated, based on ethyl cellulose (EC) 10 cps, polyethylene glycol (PEG) 4000, and diethyl phthalate (DEPh). It will hereafter be called the sparfloxacin chip (SRS chip). The chip has dimensions of 10 mm length, 2 mm width, and 0.5 mm thickness. The in vitro drug release pattern and clinical evaluation of the formulations were studied. Reports of the short-term clinical study show that the use of the SRS chip may cause complete eradication of the pathogenic bacteria in the periodontal pockets of patients who have chronic generalized periodontitis. In this clinical study, the baseline and follow-up measurements of various clinical indices, such as oral hygiene index(es), plaque index, sulcular depth component of periodontal disease index, gingival crevicular fluid flow measurement, and dark field microscopic examinations of oral pathogens in plaque samples were studied. Significant improvements were observed in many parameters of the treatment group compared with the placebo group.

Microdose gentamicin delivered via the round window microcatheter: A therapeutic option in Menière's disease

Transtympanic gentamicin therapy is becoming an increasingly popular treatment for Menière's disease. Despite its popularity, transtympanic therapy is not without controversy. Vertigo cure rates are high, but hearing loss rates are variable. The best total dose of medicine, the best route of administration, and the best end-point of therapy have not been established. Meanwhile, the mode of action of gentamicin in controlling Menière's disease is still not completely understood. In the last several years, many groups have started to use a variety of sustained release devices to more accurately control the amount of gentamicin administered to the ear. This report discusses the use of one such sustained release device, and the effects of its use with very low doses of gentamicin, on the symptoms of Menière's disease.

Microcapsules. Their Science and Technology. Part III. Industrial, Medical, and Pharmaceutical Applications.

Industrial, medical, and pharmaceutical applications of microcapsules are described. Pressure-sensitive copying paper is a typical example of their indutrial applications while sustained drug release devices are a representative example of their medical and pharmaceutical applications.

Submicron Multiphoton Free-Form Fabrication of Proteins and Polymers: Studies of Reaction Efficiencies and Applications in Sustained Release

Nonlinear multiphoton photo-cross-linking and photopolymerization of proteins and polymers in solution have been used to direct the three-dimensional assembly of micron scale objects. Two aspects of fabricated proteinatious matrixes are examined in this paper: the efficiency of protein photopolymerization and the application of fabricated matrixes as sustained release devices. The efficiency of photoactivated cross-linking of the proteins bovine serum albumin and fibrinogen, using rose bengal, have been determined and found to vary with photosensitizer concentration. This concentration dependence suggests that the mechanism for protein cross-linking is a direct hydrogen transfer between an amino acid residue of the protein and the dye molecule itself. A comparison of the surface structure of single and multiple protein oligomers is undertaken and shown to vary significantly depending on fabrication materials. Alkaline phosphatase bioactivity, upon entrapment in a protein structure, is maintained. The properties of fabricated protein matrixes as sustained release devices is also examined. The rates of diffusion of fluorescently labeled dextrans (10 and 40 kDa) from an optically fabricated BSA matrix vary with molecular weight and are linear with cross-link density. The half-life of release of 10 kDa dextran-TMR from a BSA micron scale structure is less than or equal to 6 min while 40 kDa dextran-TMR half-life of release is 25 min. Finally, rhodamine 610, a typical drug size molecule, was entrapped in an acrylamide structure, and its release is found to be diffusion-limited with half-lives of 10−31 min, depending on cross-link density.

WAAVP/Pfizer Award for Excellence in Veterinary Parasitology Research: My involvement in, and some thoughts for livestock parasitological research in Australia

Being presented with the WAAVP Pfizer award for excellence in parasitological research is the pinnacle of my career. In accepting I acknowledge the support that I have received from workmates, colleagues, friends and family over the years that I have been involved in this field of endeavour. Parasitic disease is the most significant threat to the Australian sheep industry. A lack of understanding of drug action, the absence of epidemiologically-based treatment programs and incorrect or excessive chemical use has resulted in the development of worm, lice and blowfly parasites which are resistant to most existing chemotherapeutic compounds. During the past decade, difficulties in sustainable control of parasitic disease, the decline in demand for wool products and competition from less expensive synthetic fibre has halved the sheep population and profitability of the industry. Notwithstanding this, a ‘right-sized’, sustainable industry is emerging which will require effective chemotherapy to be the cornerstone of parasite control. Chemical intervention in parasitic disease is therefore here to stay but the paucity of new antiparasitic products in the short term dictates that present therapeutics are all that producers will have for the foreseeable future. This situation will necessitate innovative practices and formulations to provide more cost effective, efficient drug performance and to extend parasiticide life. However, the development of multiple drug resistance and reduction in funds for parasitological research seriously compromises our ability to confront these demands. With the patent life of all but the most recent macrocyclic lactone (ML) compounds lapsing, low cost development of bioequivalent generic formulations and options for innovative strategies to increase performance and market share are eagerly sought. The key to efficient drug use lies in a detailed understanding of the pharmacokinetic principles of drug action and the host animal’s physiological responses to identify procedures which maximise drug availability — in essence giving the drug the best chance to work. It is therefore evident that the how, where and why of drug exchange between the bloodstream and the gastrointestinal tract are of such interest. Of particular importance is identification of the kinetic and dynamic behaviour of drug in the gastrointestinal tract (GIT) and the role of biliary secretion and metabolic fate of biliary (and non-biliary) compounds. The extent to which biliary secreted parent drug and/or metabolites are presented to the gut lumen, reabsorbed as free compound or after deconjugation by large bowel bacteria, and participate in the enterohepatic cycle is a major contributor to parasite exposure. Integrating parasiticide disposition with host physiology, particularly relating to such aspects as gastrointestinal function, feed intake and body condition has demonstrated the value of ‘whole body’ pharmacokinetic studies to identify processes to increase drug efficacy. Novel formulation modifications to provide ‘targeted’ drug delivery including carrier technology, sustained release devices and site-directed formulations can manipulate pharmacokinetic disposition to direct or extend drug availability to the parasite infection. These research directions should be undertaken as collaborative projects between research organisations and the veterinary pharmaceutical industry. With the identification of methods to improve drug action, emphasis must then be directed towards effective communication for their implementation. It will be vital that parasitologists move out of the laboratory to actively disseminate knowledge to the producer. We are ambassadors for our profession and if we fail to communicate well the perception, and indeed the value, of our work can be at risk.

Development of sustained-release devices for modulation of dental plaque biofilm and treatment of oral infectious diseases

Dental diseases are among the most prevalent human illnesses. Dental biofilm plaque harboring cariogenic bacteria (caries-associated bacteria) is the major pathogenic factor leading to dental caries. Subgingival plaque harboring periopathogenic bacteria is an additional etiological factor associated with periodontal diseases. Many pharmaceutical dosage forms are used in the prevention and treatment of these oral diseases. Toothpastes and mouthwashes are among the most popular dental medicaments. The main disadvantage of these delivery systems is their low substantivity in the target site, resulting in a low penetration coefficiency into the biofilm. A local delivery application that prolongs the release of the active agent in the mouth offers great advantages in the prevention and treatment of caries and periodontal diseases. Sustained-release varnishes, containing fluorides or antibacterial agents, have been applied to hard surfaces in the oral cavity for prevention and treatment of dental caries. Sustained-release dosage forms such as films/chips, gels, or fibers containing antibacterial agents or antiinflammatory agents have been inserted into the periodontal pocket to treat periodontal diseases. These dosage forms have been shown to reduce periopathogenic bacteria along with clinical improvements in the periodontium. An additional advantage of sustained-release devices is high patient compliance, which is an important factor in dental treatment. Sustained-release devices are a relatively new concept in the dental field. It is predicted that the use of these devices at home and in the dental clinic will increase sharply in the next decade. Drug Dev. Res. 50:555–565, 2000. © 2000 Wiley-Liss, Inc.

Swelling behavior and mechanical properties of chemically cross-linked gelatin gels for biomedical use.

Cross-linked gelatin gels are used as biomaterials in living tissues, either as bioadhesives or as devices for sustained drug release. As these applications involve surgical insertion of gels, the effect of cross-linking on mechanical properties is relevant. The effect of cross-linking on the gel water uptake is also relevant for the kinetics of drug release. Equally important is the influence of initial amounts of gelatin in the gelling solutions. We investigated the influence of cross-linking (with glutaraldehyde) and of gelatin content upon the equilibrium water content and tensile properties of resulting gels. A range of gels was prepared with gelatin contents of 10 to 40% wt, and cross-linked with 2.5 to 50% wt glutaraldehyde. The increase in gelatin content and degree of cross-linking reduced the water uptake of gels from about 60-65% wt to about 50% wt. The tensile characteristics were differentially affected. While the increase of cross-linking induced a decrease of toughness and elasticity and an increase of stiffness, it did not affect the ultimate strength of gels. On the contrary, the increase of gelatin content induced a definite increase of the ultimate strength but did not significantly affect the other properties.

Extension of the prophylactic effect of isometamidium against trypanosome infections in cattle using a biodegradable copolymer

Two trials were carried out in order to compare the prophylactic effect of a subcutaneously implanted sustained release device (SRD) containing a mixture of a biodegradable copolymer, poly(caprolactone-co- l-lactide), and isometamidium (ISMM) with that obtained after intramuscular injection of the drug. In a first experiment under controlled conditions, two groups of cattle were treated with 0.5 mg/kg isometamidium either as a SRD or intramuscularly (i.m.), and exposed at monthly intervals to Glossina morsitans morsitans infected with Trypanosoma congolense. The average protection period was at least 24 months in the SRD treated against 5.7 months in the i.m. treated group. Using an ISMM enzyme-linked immunosorbent assay, the drug could be detected until 140 days post-treatment in the latter group, whereas in the former group, traces of the drug were detectable until 330 days after treatment. Furthermore, a field trial was carried out at the Madina Diassa ranch in Mali involving three groups of N’Dama cattle, each containing 23 or 24 animals. Two groups were treated with 1 mg/kg ISMM either as a SRD or i.m. and a third group served as untreated control. Twelve months after treatment, the cumulative infection rates were 56.5, 87.8 and 91.6% in the SRD implanted, the i.m. treated and the control groups, respectively. The ISMM concentrations were slightly lower than in the laboratory trial, but the overall pattern of drug disappearance from the sera of the SRD treated cattle was very similar in both trials. Statistical analysis showed that the incidence of trypanosomiasis was significantly lower in the SRD treated than in the i.m. treated group.

Dental Drug-Delivery Devices: Local and Sustained-Release Applications

Dental diseases are among the most prevalent illnesses in humans. Many pharmaceutical dosage forms are used to prevent and treat these diseases. Toothpastes and mouthwashes are two of the most popular dental medicaments. A local delivery application that prolongs the release of the drug in the mouth offers great advantages in preventing and treating caries and periodontal diseases. Sustained-release devices are a relatively new concept in dentistry. This paper describes several types of sustained-release devices that are available commercially or are in the premarketing stage.

Biodegradable polyesters for controlled release of trypanocidal drugs: In vitro and in vivo studies

Copolymers of ε-caprolactone and l-lactide P(CL-LLA), ε-caprolactone and d,l-lactide P(CL-DLLA) and ε-caprolactone and trimethylene carbonate P(CL-TMC) were synthesized. The composition of comonomers and their sequence lengths were determined by means of 1H and 13C NMR measurements. The effect of the comonomer on the thermal properties was investigated by differential scanning calorimetry (DSC) analysis. The in vitro degradation of the rods obtained by melt extrusion of the synthesized copolymers and the commercial homopolymers poly( ε-caprolactone) P(CL) and poly( d,l-lactide) P(DLLA) was carried out in phosphate buffer (PB) pH 7.4 at 37°C. The rate of degradation depends on comonomers and polymer composition. The in vitro release of the selected drugs, isometamidium chloride (IMM) and ethidium bromide (EtBr), from such devices was carried out under the same conditions as used for the in vitro degradation. The release experiments show that the release of IMM is faster than for EtBr. During the first stage, for IMM the release is governed by osmotic pressure whereas for EtBr the release is mainly diffusion-controlled. The in vitro release of these drugs is governed by polymer matrix degradation at the later stage of the release process. Comparative in vitro release study from the different polymers showed that the release depends mainly on the physical properties of the polymer. The in vivo experiments carried out in the field on cattle and in the laboratory on rabbits using the classical treatment (intramuscular injection) and the sustained release devices (SRD) subcutaneously implanted, showed that the prophylactic period is significantly enhanced in the case of SRD as compared to intramuscular injection. The comparative efficacy of SRD containing IMM and EtBr evaluated in the case of rabbits showed that, the SRD (IMM) prophylactic period is much longer than for SRD (EtBr).

Review of insecticide resistance in cat fleas (Siphonaptera: Pulicidae).

Insecticide resistance often is blamed for failures of insecticides to control cat fleas, Ctenocephalides felis (Bouché). Yet the genetics and adaptive advantage of resistance traits remain unexamined. Lethal doses of insecticides that kill 50% of the population fluctuate 7-fold within a cat flea strain. Many reports of flea resistance may be attributable to variable mortality from effects of solvents, substrates, humidities, temperatures, colonization, and ages of fleas. Resistance ratios (ratios of lethal doses of a resistant to a susceptible strain) are < 690-fold in fleas; lower than many other arthropods. This, plus strain variability, hinders resistance detection. Relationships between resistance levels, control failures, and health threats are unclear. Insensitive acetylcholinesterase, knockdown recovery, glutathione transferase conjugation, and mixed function oxidase/cytochrome P450 are demonstrated resistance mechanisms in cat fleas. Ecological genetics of resistance in cat fleas probably involves flea transfer among hosts, host movements, refugia, founder effects, and mortality from abiotic factors. Understanding cat flea resistance requires population monitoring before, during, and after insecticide treatments using conventional and rapid molecular bioassays. Sustained insecticide release devices such as flea collars and long-lived insecticide residues for premises possibly contribute to the development of resistance. New systemic and topical insecticides, especially when given prophylactically, may act similarly. Eliminating insecticides prevents insecticide resistance but necessitates application of biorational tactics incorporating mechanical, environmental, and cultural controls. Using high temperatures, low humidities, host grooming and such tactics as decreasing doses, increasing action thresholds, rotating insecticides, and leaving spatial and temporal refugia may suppress cat flea resistance.

Estudo de sistemas acrílicos bioadesivos para liberação sustentada in vitro de fluoreto

Os autores desenvolveram dispositivos de liberação programada de fluoreto para aplicação intrabucal. O princípio ativo usado foi o fluoreto de sódio, que era associado à mistura de polimetilmetacrilato e hidroxietilmetacrilato, resinas acrílicas que formavam o sistema. Como produto acabado, os dispositivos tiveram comportamento adequado com relação à liberação de fluoreto e ao período de permanência na cavidade bucal, já que se mantiveram por um tempo relativamente elevado na boca (10 dias), liberando continuamente pequenas quantidades do agente terapêutico. Como forma de aplicação medicamentosa, estes dispositivos oferecem uma soma de vantagens, sendo a principal delas o fornecimento do princípio terapêutico no local correto (no alvo) e a manutenção constante dele neste local em concentração eficiente e segura. O desenvolvimento desses dispositivos abre campo para novas terapias.

Effect of three sustained-release devices on parasitic bronchitis in first year calves

The effect of three intraruminal sustained-release devices (SRD) against Dictyocaulus viviparus infection was tested in five groups of six calves. Group 1 served as untreated controls, and groups 2, 3...

Field evaluation of the prophylactic effect of an isometamidium sustained-release device against trypanosomiasis in cattle.

In order to compare the prophylactic effect provided by a poly(D,L-lactide) sustained-release device (SRD) containing isometamidium (ISMM) with that provided by the classical intramuscular injection of the drug, a field trial was carried out at the Madina Diassa Ranch in Mali. One- to 3-year-old N'Dama cattle were randomly divided into three groups. The first group (n = 42) was treated with ISMM at a dose of 1 mg/kg of body weight, the second group (n = 44) received the same dose of the drug via an SRD, which was subcutaneously implanted in the shoulder region, and the third group (n = 36) was kept as an untreated control group. All animals were treated with diminazene aceturate (7 mg/kg of body weight) 2 weeks before the start of the experiment and were tested monthly by the buffy coat technique for a period of 8 months. Glossina morsitans submorsitans was the most important tsetse species, with apparent densities (number of catches/trap/day) varying between 11.9 and 38.7 over the experimental period. Eight months after treatment the cumulative infection rates were 27.7, 58.5, and 77.4% in the group with the SRD implant, the group receiving the intramuscular injection, and the control group, respectively. Statistical analysis showed that the incidence of trypanosomiasis was significantly lower (P = 0.006) in the group which received ISMM via the SRD than in the one which was treated with ISMM intramuscularly.