PATIENTS' KNOWLEDGE OF MEDICAL PATCHES IN HUNGARY.

Transdermal therapy with medical patches is a simple possibility in home medication. As the correct use of patches has a decisive impact from the point of its modulator effect.A questionnaire survey was developed to explore level of patients' knowledge of the correct use of transdermal patches. A survey was administered in thirteen Hungarian community pharmacies from October of 2012 to May of 2015. Most of the participants, men and women over 18 years of age (n = 233), used major analgesic patches (fentanyl); the remainder were given nitroglycerin, NSAID analgesics patches during the survey. For the hypothesis testing it was assumed that men were more likely to use a razor for skin depilation before patch application than women as their denser pelage hinders patch adhesion. The hypothesis testing showed no significant gender difference in razor use (X² = 0.201; p = 0.654). Pharmacists should direct patients to avoid using soap for skin cleansing before patch application because only 22 percent of the participants always avoided its use. Since only 9 tests were flawless from 233 completed questionnaires. Many patients do not understand how to correctly apply a transdermal dosage patch. Pharmacists should teach their correct application based on results.

A comparison of three different methodologies for evaluating Rhipicephalus (Boophilus) microplus susceptibility to topical spray compounds.

This study aimed to compare three different methodologies (Adult Immersion Tests, field trials with naturally infected animals, and a Stall Test using artificially infested cattle) to evaluate the efficacy of two topical formulations that we administered as whole body sprays (15% Cypermethrin+30% Chlorpyriphos+15% Fenthion-Colosso(®) FC 30, Ouro Fino Agronegócios; and 60% Dichlorvos+20% Chlorpyriphos-Ectofós(®), Vallée Saúde Animal Ltd.), against a susceptible strain of Rhipicephalus (Boophilus) microplus. To achieve this objective, two natural infestation trials were conducted, as well as two artificial infestation trials (Stall Tests) and two Adult Immersion Tests (AIT). The AIT results showed that both spray formulations achieved 100% efficacy against R. (B.) microplus fully engorged females. However, when observing results obtained by field trials (natural infestations) and Stall Tests, none of these topically applied compounds reached 100% efficacy or affected the reproductive capacity of the fully engorged female ticks. Additional studies must be conducted to compare these in vivo methodologies with different in vitro techniques, such as the Larval Packet Test. However, based on results obtained here, we can conclude that depending on the spray formulations used, the AIT can overestimate acaricidal efficacy and values of reproductive efficiency of such compounds against R (B.) microplus. Specifically, when dealing with spray formulations in the Stall Tests, the period of residual action can increase because these animals are sheltered from contact with environmental factors that might interfere with the efficacy of the products tested. It may be necessary to take in vivo trial results into consideration (such as field trials with naturally infested animals or Stall Tests) to standardize a specific in vitro assay, such as the Adult Immersion Test.

The participation of human hepatic P450 isoforms, flavin-containing monooxygenases and aldehyde oxidase in the biotransformation of the insecticide fenthion.

Although fenthion (FEN) is widely used as a broad spectrum insecticide on various crops in many countries, very scant data are available on its biotransformation in humans. In this study the in vitro human hepatic FEN biotransformation was characterized, identifying the relative contributions of cytochrome P450 (CYPs) and/or flavin-containing monooxygenase (FMOs) by using single c-DNA expressed human enzymes, human liver microsomes and cytosol and CYP/FMO-specific inhibitors. Two major metabolites, FEN-sulfoxide and FEN-oxon (FOX), are formed by some CYPs although at very different levels, depending on the relative CYP hepatic content. Formation of further oxidation products and the reduction of FEN-sulfoxide back to FEN by the cytosolic aldehyde oxidase enzyme were ruled out. Comparing intrinsic clearance values, FOX formation seemed to be favored and at low FEN concentrations CYP2B6 and 1A2 are mainly involved in its formation. At higher levels, a more widespread CYP involvement was evident, as in the case of FEN-sulfoxide, although a higher efficiency of CYP2C family was suggested. Hepatic FMOs were able to catalyze only sulfoxide formation, but at low FEN concentrations hepatic FEN sulfoxidation is predominantly P450-driven. Indeed, the contribution of the hepatic isoforms FMO(3) and FMO(5) was generally negligible, although at high FEN concentrations FMO's showed activities comparable to the active CYPs, accounting for up to 30% of total sulfoxidation. Recombinant FMO(1) showed the highest efficiency with respect to CYPs and the other FMOs, but it is not expressed in the adult human liver. This suggests that FMO(1)-catalysed sulfoxidation may represent the major extra-hepatic pathway of FEN biotransformation.

Modulation of fenthion-induced oxidative effects by BSO in the liver of Cyprinus carpio L.

The objective of the present study was to evaluate the oxidative stress potential of low-level organophosphate fenthion exposure with the modulatory effect of buthionine sulfoximine in the liver of Cyprinus carpio L. The fish were exposed to 20% of 96-hour LC(50) of fenthion for 24 and 96 hours. Total and oxidized glutathione, thiobarbituric acid reactive substances, protein levels, glutathione peroxidase, glutathione reductase, glutathione-S-transferase, superoxide dismutase, and catalase-specific enzyme activities were measured spectrophotometrically. There was a 15-day depuration period to evaluate the changes in the studied parameters. Fenthion caused a time-dependent depletion of the total and reduced glutathione levels. The oxidized/reduced glutathione ratio and catalase specific enzyme activity were reduced while the glutathione-S-transferase activity was elevated. Intraperitonal buthionine sulfoximine application disclosed the inhibitory effect of fenthion on superoxide dismutase and glutathione peroxidase activities, whereas glutathione-S-transferase activity was increased. There was no change in lipid peroxidation levels during the experiments. No amelioration was observed in the affected parameters except the glutathione-S-transferase activity in the 15-day depuration period. In conclusion, glutathione-S-transferase and catalase enzyme activities and total and reduced glutathione levels were better estimators to monitor the effects of fenthion in low concentration in the liver of C. carpio. The depuration period was not adequate to recover the antioxidant capacity.

Prolonged cholinergic crisis and compartment syndrome following subcutaneous injection of an organophosphate compound for suicide attempt.

A case of poisoning with highly lipid soluble organophosphate compound, fenthion is reported in which cholinergic crisis recurred upto 25 days following a suicide attempt. Subcutaneous injection of fenthion in the antecubital fossa by the patient produced massive swelling, cellulitis and compartment syndrome of the left arm. Emergency fasciotomy helped in restoration of circulation and saved the limb from being amputated.

Influence of atropine therapy on fenthion-induced pancreatitis.

OBJECTIVE: We searched the influence of dose and timing of atropine therapy in fenthion-induced pancreatitis model. METHODS: All rats were intoxicated with fenthion except the control group. Two milligrams of atropine was administered for 24 hours in a high dose atropine group while a low dose atropine group received 100 micrograms of atropine for 24 hours. One group received 2 milligrams of atropine in the first four hours of intoxication while the other group received 2 milligrams of atropine in the last four hours before sacrifice. All rats were sacrificed 24 hours after intoxication. Pseudo-cholinesterase and lipase concentrations and histopathological markers of pancreatitis were studied. RESULTS: None of the models in this study completely prevented pancreatitis, however high dose atropine that is administered for 24 hours or the first four hours after intoxication prevented severe pancreatitis. CONCLUSION: Atropine administration influence on fenthion-induced pancreatitis should be studied for other organophosphates in animals and humans.

Continuous, mixed, and alternating exposure to deltamethrin and fenthion affect development of resistance in Culex pipiens pallens in China.

A field population of Culex pipiens pallens was collected from Nanjing, China on July in 2000 and reared in an insectarium. Larvae were subjected to single, mixed, and alternating exposure to deltamethrin and/or fenthion, and the surviving early 4th instars were reared for establishment of adult colonies. Larvae from the colonies were then subjected to the same selection pressures over the subsequent 15 generations. Resistance rates and ratios were measured as LC50 values derived from larval bioassays. In populations exposed to deltamethrin or fenthion alone (single exposure), resistance levels rose rapidly. The LC50 values for deltamethrin and fenthion alone were 29.3 and 1.565 mg/liter, respectively, and the ratios of resistance were 697.6- and 24.8-fold, respectively. Exposure to a mixture of deltamethrin and fenthion (1:1; mixed selection) reduced the development of resistance. The LC50 value and ratio of resistance for the mixture of deltamethrin and fenthion were 0.607 mg/liter and 14.8-fold, respectively, at generation 15. Exposure to alternating treatments of deltamethrin and fenthion (alternating selection) showed an even lower development of resistance. For the alternating treatments, the LC50 value and ratio of resistance to deltamethrin were 0.795 mg/liter and 17.7-fold, respectively (generation 14), and those to fenthion were 0.219 mg/liter and 3.6-fold, respectively (generation 15). Together, these results indicate that the single continuous insecticide selection generated a much more severe resistance than a mixture and/or alternating treatments.

Beneficial effect of N-acetylcysteine against organophosphate toxicity in mice.

Recent studies showed that oxidative stress could be an important component of the mechanism of organophosphate (OP) compounds toxicity. The aim of present study was to investigate either prophylactic and therapeutic effects of N-acetylcysteine (NAC) against fenthion-induced oxidative stress in mice. Additionally, the effects on survival rates were investigated. Therefore, we determined the changes of the blood levels of glutathione (GSH), malondialdehyde (MDA), nitrite, and nitrate in blood or serum. Additionally, all animals were observed for 6 h and the survival rates were recorded. It was found that fenthion administration increased the levels of MDA, and decreased the levels of GSH, nitrite and nitrate. On the other hand, both prophylactic and therapeutic NAC treatment decreased the levels of MDA, and increased the levels of GSH, nitrite, and nitrate. The results showed that NAC is able to attenuate the fenthion-induced oxidative stress whereby NAC has not only prophylactic but also therapeutic activity in fenthion poisoning. On the other hand, we found that NAC can clearly improve survival rates in mice administered with an acute high dose of fenthion poisoning. In conclusion, NAC can decrease OP-induced oxidative stress and mortality rate, but the exact mechanism of its NAC protective effect needs to be explored further.

A comparison of two ultra-low-volume spray nozzle systems by using a multiple swath scenario for the aerial application of fenthion against adult mosquitoes.

Two hydraulic spray nozzle systems, a flat fan and a high-pressure hollow cone, were used for ultra-low-volume application of the mosquito adulticide fenthion under a multiple swath scheme. Eight swaths at 322-m intervals were applied from a height of 91 m to simulate operational conditions. Deposition, effects on nontarget organisms (fiddler crabs), aerial flux, and mosquito (Ochlerotatus taeniorhynchus) mortality were monitored for 8,230 m downwind, including the area under all 8 swaths. The flat-fan nozzle system deposited 88 times the amount of fenthion deposited by the high-pressure system in a lightly vegetated zone directly beneath the application area (0-2,134 m). Further downwind (2,286-4,420 m) in the 2nd semiopen urban zone, 10.5 times more chemical was deposited with the flat-fan nozzles than with the high-pressure nozzles, and in the 3rd highly vegetated zone (4,572-8,230 m), 25 times more was deposited compared with high-pressure nozzles. The corresponding nontarget mortalities with the flat-fan nozzle were 80, 12, and 17% at 2,438, 3,658, and 4,572 m, respectively. No treatment-induced mortality was observed with high-pressure nozzles. Similar amounts of fenthion residue were recovered from yarn samples for both nozzle systems, with the exception of the zone directly under the flight paths, where the flat-fan system deposited 2.5 times the amount recovered with the high-pressure system. Mosquito mortality was similar between the 2 nozzle types except in the farthest zone, where the average mortalities for the high-pressure system and the flat-fan system were 73.4 and 34.8%, respectively. Regression analysis of the mosquito mortality and yarn samples showed that the high-pressure hollow-cone application could control mosquitoes with half the amount of chemical compared to flat-fan nozzles.

A comparison of two spray nozzle systems used to aerially apply the ultra-low-volume adulticide fenthion.

Field experiments with the mosquito adulticide fenthion (Baytex) compared the conventional flat-fan nozzle system (Tee Jet 8002SS) and a new high-pressure hollow-cone nozzle system (1/8 MISS). Ground deposition and aerial flux of the mosquito adulticide fenthion were measured up to 4.83 km downwind by using filter paper and yarn collectors, respectively. Biological efficacy was investigated by using caged salt-marsh mosquitoes (Ochlerotatus taeniorhynchus), and caged fiddler crabs (Uca pugilator) were exposed to quantify nontarget impact. Peak deposits to the ground were 1,729 microg/m2 and 240 microg/m2 for the flat-fan nozzles and high-pressure cones, respectively. Deposits from the flat-fan nozzles resulted in a cumulative fiddler crab mortality of 80%, whereas no deaths were recorded with the high-pressure system. The range of fenthion flux detected in the air when using the yarn collectors was similar for the 2 systems, with both showing drift through 4.83 km. For the flat-fan spray nozzle system, the aerosol flux ranged from 3.02 to 67.33 microg/yarn collector. The range of aerosol flux for the high-pressure nozzle spray system was 0.15-50.66 microg/yarn collector. Although the 2 systems produced comparable ranges of flux, the high-pressure system provided higher control efficacy against mosquitoes. Maximum mosquito control when using the flat-fan spray nozzle system against female salt-marsh mosquitoes was 26.6%, whereas maximum control with the high-pressure spray system was 92.9%.

Ground deposition impact of aerially applied fenthion on the fiddler crabs, Uca pugilator.

Caged fiddler crabs, Uca pugilator, were exposed to field ULV applications to measure the impact of fenthion. Two nozzle systems, conventional flat-fan nozzles (Tee Jet 8002SS) and high-pressure hydraulic nozzles (1/8 MIS), were compared using single spray swaths. Fenthion residues were detected throughout the 4.83-km test zone for both systems. Heavy ground deposits (650-1,670 microg/m2) of fenthion were found within 1 km using the flat-fan nozzle systems, which resulted in 80% fiddler crab mortality. Less than 100 microg/m2 fenthion ground deposits were detected during the high-pressure nozzle trials. No fiddler crab mortality was observed within the first 1-km zone following 3 single swath applications repeated during 3 consecutive nights. We found also that when the fiddler crabs were exposed to 700-800 microg/m2 fenthion, mortality occurred. Significant crab mortality (>50%) was observed when residues exceeded 1,000 microg/m2.

Severe fenthion intoxications due to ingestion and inhalation with survival outcome.

Two cases of severe fenthion intoxication are presented. The first is a case of a psychiatric patient who attempted suicide with ingestion of the compound, and the second case was of a child exposed to the chemical agent by air spraying. Both patients were treated in the intensive care unit with atropine and pralidoxime and finally survived. Fenthion blood levels on admission were 2.7 and 0.95 microg/mL, respectively. Different concentrations of pralidoxime were added to the first patient's poisoned serum in order to assess in vitro the effect of pralidoxime on cholinesterase reactivation. The clinical and toxicological data of the poisonings are discussed, as well as the potential therapeutic use of pralidoxime in organophosphate intoxication.

Topical insecticide treatments to protect dogs from sand fly vectors of leishmaniasis.

We compared the susceptibility of sand fly vectors to four topical insecticide treatments applied to domestic dogs, a reservoir of human leishmaniasis. Dogs were exposed to sand flies pretreatment and at 1 week, 1 month, and 2 months posttreatment. Sand fly bloodfeeding and survival rate of both fed and unfed flies were significantly reduced by the permethrin, deltamethrin, and fenthion treatments, but diazinon had no effect. The survival rate of bloodfed sand flies was reduced by up to 86% with deltamethrin collars. The antifeeding effect suggests that deltamethrin collars may be recommended to dog owners to protect their pets from sandfly- borne diseases. The combined effects on sand fly feeding and survival indicate that epidemiologic, community-based trials are warranted to test whether deltamethrin collars could reduce the incidence of canine and, hence, human leishmaniasis.

Parasuicide by self-injection of an organophosphate insecticide.

Parasuicide by ingestion of organophosphate (OP) insecticides is common in Sri Lanka, but the use of the parateral route to self administer the poison is extremely rare. We report a patient who deliberately injected herself intramuscularly with an OP compound with suicidal intent. The clinical manifestations of OP poisoning were unpredictable and posed a therapeutic problem.

Analysis of the use of fenthion via epicutaneous in dogs for Rhipicephalus sanguineus control.

The action of fenthion was studied in a 15% epicutaneous formulation upon Rhipicephalus sanguineus, which may transmit pathogens to men and other animals, such as Ehrlichia, Babesia and Ricketsia. Dogs were artificially infected for the trial. The fenthion bioassays were begun four months after artificial infestation. The test group, having a mean of 186 ticks per dog, received the formulation dosage according to body weight on the neck region. Tick counts were performed, considering diameters > or = 2mm, during 11 days of treatment, in the most affected body areas: back, ears and paws. Before the application of fenthion in the dogs, it were observed an average 43.3% ticks in the ears, 38.1% in the back area and 17.6% in the paws. The number of ticks in dogs decreased by 36.2%, 63.8%, 82.7%, 67%, 40% and 4.9%, respectively on days 1, 2, 3, 5, 7, 9 and 11 after treatment. R. sanguineus anti-tick activity, lower than that officially recommended, was verified. The number of ticks increased progressively after the 5th day, demonstrating residual insecticide inefficacy. The results obtained did not indicate the use of this formulation, at the tested dosage, as an elective measure for R. sanguineus control.

Analysis of the use of fenthion via epicutaneous in dogs for Rhipicephalus sanguineus control

The action of fenthion was studied in a 15% epicutaneous formulation upon Rhipicephalus sanguineus, which may transmit pathogens to men and other animals, such as Ehrlichia, Babesia and Ricketsia. Dogs were artificially infected for the trial. The fenthion bioassays were begun four months after artificial infestation. The test group, having a mean of 186 ticks per dog, received the formulation dosage according to body weight on the neck region. Tick counts were performed, considering diameters > or = 2mm, during 11 days of treatment, in the most affected body areas: back, ears and paws. Before the application of fenthion in the dogs, it were observed an average 43.3% ticks in the ears, 38.1% in the back area and 17.6% in the paws. The number of ticks in dogs decreased by 36.2%, 63.8%, 82.7%, 67%, 40% and 4.9%, respectively on days 1, 2, 3, 5, 7, 9 and 11 after treatment. R. sanguineus anti-tick activity, lower than that officially recommended, was verified. The number of ticks increased progressively after the 5th day, demonstrating residual insecticide inefficacy. The results obtained did not indicate the use of this formulation, at the tested dosage, as an elective measure for R. sanguineus control.

Investigou-se a atividade de fenthion em formulação epicutânea a 15% sobre Rhipicephalus sanguineus, transmissor de patógenos ao homem e animais, tais como Ehrlichia, Babesia e Ricketsia. Infestou-se artificialmente cães com larvas deste carrapato. Os bioensaios com o fenthion iniciaram-se 4 meses após a infestação artificial. Constatada a média de 186 ixodídeos/cão, cães do grupo teste receberam na região da nuca a dosagem correspondente ao seu peso. Avaliaram-se a eficiência e a atividade residual através de contagens dos carrapatos com diâmetro ³ 2mm, durante 11 dias, nas áreas corpóreas mais parasitadas: dorso, orelhas e patas. Anteriormente, à aplicação do fenthion, 44,3% dos carrapatos format observados nas orelhas, 38,1% na área estudada do dorso e 17,6% nas patas. Revelou-se uma redução do número de carrapatos nos cães de 36,2%, 63,8%, 82,7%, 67%, 40% e 4,9%, respectivamente, nos dias 1, 2, 3, 5, 7, 9 e 11. Atividade carrapaticida menor do que a recomendada oficialmente foi constatada. O número de carrapatos aumentou progressivamente após o 5° dia, denotando ineficácia carrapaticida residual. Os resultados obtidos impedem a indicação da formulação na dosagem testada como medida eletiva para controle de R. sanguineus.

Relative cost-effectiveness of treatment of feedlot calves with ivermectin versus treatment with a combination of fenbendazole, permethrin, and fenthion.

OBJECTIVE: To compare growth performance, animal health characteristics, and carcass characteristics of feedlot calves treated with ivermectin topically with that of feedlot calves treated with a combination of fenbendazole orally and permethrin and fenthion topically. DESIGN: Clinical trial. ANIMALS: 14,184 British crossbred steer calves (mean weight, 286 kg [630 lb]) in 30 pens at a commercial feedlot in Nebraska. PROCEDURE: On arrival at the feedlot, calves were randomly assigned to be treated with ivermectin topically or with a combination of fenbendazole orally and permethrin and fenthion topically (control). At the time of assignment to treatment groups, fecal samples were collected from 5% of the calves. Growth performance, carcass characteristics, and health information were recorded. RESULTS: Geometric mean fecal egg counts at the time of arrival at the feedlot were not significantly different between groups. Final weight, weight gain, average daily gain, and the dry matter intake-to-gain ratio were significantly improved for calves in the ivermectin group. The percentage of carcasses classified as quality grade choice was higher for the ivermectin group than the control group; however, the percentage of carcasses classified as yield grade 1 and the dressing percentage were higher for the control group than for the ivermectin group. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that topical administration of ivermectin to feedlot calves is relatively more cost-effective than administration of a combination of fenbendazole orally and permethrin and fenthion topically.

Insecticide susceptibility status of Culex tritaeniorhynchus giles, vector of Japanese encephalitis in Delhi.

Laboratory studies were carried out to ascertain the current susceptibility status of adult and larval stages of the Culex tritaeniorhynchus mosquito, vector of Japanese encephalitis, to various insecticides used under public health programs in India. The present study revealed that exposure of adult mosquitoes to diagnostic concentrations of DDT - 4.0%, malathion - 5.0%, fenitrothion - 1.0%, and propoxur - 0.1% could induce only 50.0, 10. 0, 15.0, and 5.0% mortality, respectively, indicating that the species was resistant to all of these insecticides. The LT50 and LT95 values calculated using diagnostic concentrations of DDT, malathion, fenitrothion, and propoxur were found to be 56.4 and 136, 138 and 272, 185 and 258, and 187 and 249 min, respectively. However, when adult mosquitoes were exposed to the diagnostic concentration of synthetic pyrethroids, viz., deltamethrin - 0.025%, permethrin - 0.25%, and lambdacyhalothrin - 0.1%, 100.0% mortality was observed, indicating that the species was highly susceptible to these adulticides. Larval susceptibility tests carried out using diagnostic dosages of DDT- 0.008, temephos- 0.02, fenthion- 0.008, fenitrothion- 0.125, and malathion- 0.005 mg/l failed to induce any mortality, indicating that larvae were resistant to these larvicides. The LC50 and LC90 values calculated for commonly used larvicides, viz., temephos and fenthion, were 0.1511 and 1.9098, and 0.6151 and 2.395 mg/l, respectively. Increase in tolerance level were estimated at 95.5- and 299.4-fold when these LC90 values were compared with diagnostic dosages of temephos and fenthion, respectively.

Comparative cost-effectiveness of ivermectin versus topical organophosphate in feedlot yearlings.

A replicated-pen field trial was performed under commercial feedlot conditions in western Canada to determine the cost-effectiveness of administering ivermectin to yearling beef cattle upon entry to the feedlot after the grazing season, and to establish the level of trichostrongylid gastrointestinal parasite infection in this population, as estimated by fecal egg counts. Six thousand eight hundred and eighty-three, mixed breed, yearling steers were randomly allocated upon arrival at the feedlot to one of 2 experimental groups as follows: Ivermectin, which received topical ivermectin (0.5%) at the rate of 1.0 mL/10 kg body weight; or Fenthion, which received topical fenthion (20%) at the rate of 12 mL/295 kg body weight. There were 15 pens in each experimental group. Final weight, weight gain, average daily gain, and dry matter intake to gain ratio were significantly (P < 0.05) improved in the Ivermectin group as compared with the Fenthion group. There were no significant (P > or = 0.05) differences in initial weight, days on feed, or daily dry matter intake between the experimental groups. The geometric mean fecal egg counts at the time of allocation were 14.7 eggs/5 g and 16.6 eggs/5 g for the Ivermectin and Fenthion groups, respectively (P > or = 0.05). There were no significant (P > or = 0.05) differences in morbidity or mortality between the experimental groups. In the economic analysis, the significant improvements in feedlot performance in the Ivermectin group resulted in a net economic advantage of $4.20 CDN per animal.

Comparison of ivermectin SR bolus, benzimidazole anthelmintics, and topical fenthion on productivity of stocker cattle from grazing through feedlot.

A study was conducted to determine the effect of different parasite control programs on weight gain and other measurements for stocker beef calves during the grazing season and subsequent feedlot phase of production. One hundred eighty recently weaned beef steers were purchased from a Mississippi sale barn and were allocated by restricted randomization on pretreatment weight to three treatments: (1) no anthelmintic treatment; treated only with a topical organophosphate (OP) during processing into the feedlot; (2) one benzimidazole (BZD) treatment at initiation of grazing, and a second given at the time of processing upon arrival at the feedlot, along with a topical OP; and (3) ivermectin sustained-release (SR) bolus administered at initiation of grazing, with no further treatment given at the feedlot. The cattle grazed separately by treatment for 125 days, with six replicated pastures per treatment; then were penned according to the same groupings after entry into the feedlot on day 127. Cattle were individually weighed at approximately 2-month intervals, and feed consumption was measured during the 167 days in the feedlot. Fecal nematode egg counts were individually monitored for all animals during both phases of the trial. Carcass weight, quality grade, yield grade, and the incidence of liver abscesses were recorded for each animal at slaughter. Cattle treated with the ivermectin SR bolus gained significantly (P < .05) more weight through the grazing period and from the start of grazing through the end of the feedlot phase than the controls or the cattle treated with BZD products. There were no significant differences in feed efficiency between any of the groups. Mean carcass weight for cattle treated with boluses was significantly (P < .05) greater than that of the controls and the group treated with BZD. Dressing percentage and quality grade were significantly (P < .05) higher for the BZD and bolus groups, and yield grade was slightly (but not significantly) better for each of these groups than for controls. Significantly (P < .05) fewer livers of cattle treated with boluses had abscesses at slaughter than did livers of controls or cattle treated with BZDs. During both phases of the trial, fecal egg counts were significantly (P < .05) lower for the group treated with boluses than for the untreated group or the group treated with BZD. These data indicate that treatment with boluses for parasite control at the beginning of the grazing period had beneficial effects on weight gain as compared to no anthelmintic treatment or treatment with a BZD at the start of grazing and again at the time of introduction into the feedlot. These bolus benefits were sustained through the feedlot phase of production and provided further improvements with significantly (P < .05) increased carcass weights. The bolus is a tool that can significantly increase the efficiency of production for cattle producers who retain ownership into the feedlot phase of production or feedlot operators who graze stockers before feedlot entry.