Browsing by Author "Akşit, Dilek"

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Comparative plasma and milk dispositions, faecal excretion and efficacy of per os ivermectin and pour-on eprinomectin in horses
(Wiley, 2016-03-07) Gökbulut, Cengiz; Akşit, Dilek; Aksöz, Elif; Korkut, Oğuzhan; Yalçınkaya, M.; Özüiçli, Mehmet; Çırak, Veli Yılgör; Uludağ Üniversitesi/Veteriner Fakültesi/Parazitoloji Anabilim Dalı.; 57188556574; 6602404057
The horse milk gains increasing interest as a food product for sensitive consumers, such as children with food allergies or elderly people. We investigated the plasma and milk disposition, faecal excretion and efficacy of per os ivermectin (IVM) and pour-on eprinomectin (EPM) in horses. Ten mares were divided into two groups. The equine paste formulation of IVM and bovine pour-on formulation of EPM were administered orally and topically at dosage of 0.2 and 0.5 mg/kg bodyweight. Blood, milk and faecal samples were analysed using high-performance liquid chromatography. The plasma concentration and persistence of IVM were significantly greater and longer compared with those of EPM. Surprisingly, EPM displayed a much higher disposition rate into milk (AUC(milk/plasma): 0.48) than IVM (AUC(milk/plasma): 0.19). IVM exhibited significantly higher faecal excretion (AUC(faeces): 7148.54 ng.d/g) but shorter faecal persistence (MRTfaeces: 1.17 days) compared with EPM (AUC(faeces): 42.43 ng.d/g and MRTfaeces: 3.29 days). Faecal strongyle egg counts (EPG) were performed before and at weekly intervals after treatment. IVM reduced the EPG by 96-100% for up to 8 weeks, whereas the reduction in the EPM group varied from 78 to 99%. In conclusion, due to the relatively low excretion in milk, EPM and IVM may be used safely in lactating mares if their milk is used for human consumption. Nevertheless, much lower plasma and faecal availabilities of EPM could result in subtherapeutic concentrations, which may increase the risk of drug resistance in nematodes after pour-on EPM administration compared with per os IVM.
Comparative plasma disposition, bioavailability and efficacy of ivermectin following oral and pour-on administrations in horses
(Elsevier, 2010-05-28) Gökbulut, Cengiz; Akşit, Dilek; McKellar, Quintin A.; Çırak, Veli Yılgör; Şenlik, Bayram; Durmaz, Murat; Uludağ Üniversitesi/Veterinerlik Fakültesi/Klinik Öncesi Bilimler Bölümü.; 0000-0002-1817-5744; 0000-0003-2964-2245; 6602404057; 9332720500; 16039333100
Pour-on formulations of endectocides decrease the risk of injury for both user and animal, and are particularly convenient for animal owners who can apply the product. This study was designed to investigate the plasma disposition and efficacy of ivermectin (IVM) following pour-on, per os and intravenous administrations. Eighteen female horses weighing 510-610 kg were used in this study. The animals were allocated into three groups (per os, pour-on and intravenous groups). The equine paste, bovine pour-on and bovine injectable formulations of IVM were administered orally, topically and intravenously at the dose rates of 0.2, 0.5 and 0.2 mg/kg bodyweight, respectively. Heparinized blood samples and hair samples were collected at various times between 1 h and 40 days. The samples were analysed by high performance liquid chromatography with fluorescence detector. Faecal strongyle egg counts (EPG) were performed by a modified McMaster's technique before and at weekly intervals during 10 weeks after treatment. The results indicated that the plasma concentration and systemic availability of IVM was lower but the plasma persistence was prolonged after pour-on administration compared with per os route. IVM (paste) reduced the EPG by >95% for 10 weeks, whereas the reduction in pour-on group varied from 82 to 97%. EPG reduction in pour-on group was lower than that of per os group. Degradation on the application site, cutaneous biotransformation, binding of IVM to the haircoat and/or sebum are probably responsible for the relatively lower bioavailability of IVM in horses after pour-on administration. In conclusion, the poor plasma availability observed after pour-on administration could result in subtherapeutic plasma concentrations, which may promote the development of drug resistance in parasites.
The effects of different ages and dosages on the plasma disposition and hair concentration profile of ivermectin following pour-on administration in goats
(Wiley, 2011-02) Gökbulut, Cengiz; Akşit, Dilek; McKellar, Quintin A.; Çırak, Veli Yılgör; Şenlik, Bayram; Uludağ Üniversitesi/Veteriner Fakültesi/Parazitoloji Anabilim Dalı.; 0000-0003-2964-2245; 6602404057; 9332720500
The effects of different ages and dosages on the plasma disposition and hair degradation of ivermectin (IVM) were investigated following pour-on administration in goats. Twenty-eight female Saanen goats allocated into two groups of 14 animals according to their ages as young (5-6 months old) and old (12-24 months old) groups. Each age group was divided into two further of seven goats and administered pour-on formulation of IVM topically at the in recommended dosage rate of 0.5 mg/kg bodyweight The recommended cattle dosages rate of 0.5 mg/kg or at the higher dosage of 1.0 mg/kg. Blood samples were collected at various times between 1 h and 40 days. In addition, hair samples (> 0.01 g) were collected using tweezers from the application sites and far from application sites of the all animals throughout the blood sampling period. The plasma and hair samples were analyzed by high performance liquid chromatography (HPLC) using fluorescence detection following solid and liquid phase extractions, respectively. Dose- and age-dependent plasma disposition of IVM were observed in goats after pour-on administration. In addition, relatively high concentration and slow degradation of IVM in hair samples collected from the application site and far from the application site were observed in the present study. The differences between young and old goats are probably related to differences in body condition and/or lengths of haircoat. The systemic availability of IVM following pour-on administration is relatively much lower than after oral and subcutaneous administrations but the plasma persistence was prolonged. Although, the longer persistence of IVM on hairs on the application site may prolong of efficacy against ectoparasites, the poor plasma availability could result in subtherapeutic plasma concentrations, which may confer the risk of resistance development in for internal parasites after pour-on administration in goats.
Plasma dispositions and concentrations of ivermectin in eggs following treatment of laying hens
(Taylor & Francis, 2018-01-05) Akşit, Dilek; Gökbulut, C.; Çırak, Veli Yılgör; Cihan, Hüseyin; Uludağ Üniversitesi/Veteriner Fakültesi/Parazitoloji Anabilim Dalı.; Uludağ Üniversitesi/Veteriner Fakültesi/İç Hastalıkları Anabilim Dalı.; 0000-0003-1544-6438; ABH-3742-2020; 6602404057; 6602381681
AIMS: To determine the plasma disposition and concentrations of ivermectin (IVM) in eggs produced by laying hens following S/C, oral and I/V administration.METHODS: Twenty-four laying hens, aged 37 weeks and weighing 1.73 (SD 0.12) kg were allocated to three groups of eight birds. The injectable formulation of IVM was administered either orally, S/C, or I/V, at a dose of 0.2mg/kg liveweight, following dilution (1:5, v/v) with propylene glycol. Heparinised blood samples were collected at various times between 0.25 hours and 20 days after drug administration. Eggs produced by hens were also collected daily throughout the study period. Samples of plasma and homogenised egg were analysed using HPLC.RESULTS: Maximum concentrations of IVM in plasma and mean residence time of IVM were lower after oral (10.2 (SD 7.2) ng/mL and 0.38 (SD 0.14) days, respectively) than after S/C (82.9 (SD 12.4) ng/mL and 1.05 (SD 0.24) days, respectively) administration (p<0.01). The time to maximum concentration and elimination half-life were shorter following oral (0.14 (SD 0.04) and 0.23 (SD 0.11) days, respectively) than S/C (0.25 (SD 0.00) and 1.45 (SD 0.45) days, respectively) administration (p<0.01). IVM was first detected in eggs 2 days after treatment in all groups and was detected until 8 days after oral and I/V administration, and until 15 days after S/C administration. Peak concentrations of IVM were 15.7, 23.3 and 1.9 mu g/kg, observed 2, 5 and 4 days after I/V, S/C and oral administration, respectively.CONCLUSIONS AND CLINICAL RELEVANCE: The low plasma bioavailability of IVM observed after oral administration in laying hens could result in lower efficacy or subtherapeutic plasma concentrations, which may promote the development of parasitic drug resistance. Due to high IVM residues in eggs compared to the maximum residue limits for other food-producing animal species, a withdrawal period should be necessary for eggs after IVM treatment in laying hens.