Is the suckling period and application pattern relevant for fluazuron against tick infestation in cows and their suckling calves?

BACKGROUND: Fluazuron is a chitin synthesis inhibitor administered as a pour-on formulation in cattle for tick control. This study analyzes under endemic tick infestation, the incidence of the pour-on application pattern on the plasma levels of fluazuron in calves and cows in the lactation period of the beef cow. Two hundred and ninety-two beef cows around parturition were treated with a commercial pour-on formulation of fluazuron at a rate of 2.5 mg/kg of body weight. A total of 4 treatments were carried out on days 0, 32, 77, and 117. At each administration time, the cows were grouped according to the pour-on administration pattern: long (~ 60 cm pour-on application surface) and short (~ 30 cm pour-on application surface). Fluazuron levels in cows and calves plasma were determined before the third and fourth application for each subgroup (n = 10) by HPLC-MS/MS. During the entire study, cow-calf pairs were maintained under field conditions and qualitatively examined for tick infestation on the day of each treatment. Both treatments (long and short) schemes were designed to prevent the annual persistence of ticks. RESULTS: No animals with presence of ticks were identified during the first 117 days of the study, except for three cows and one calf at the time of the third application (day 77). There were no differences after 40 days (day 77) post-treatment of the second application (30 ± 5 ppb vs. 28.5 ± 12 ppb, p > 0.05) and 45 days (day 117) after the third application (147 ± 55 ppb vs 140 ± 46 ppb, p > 0.05) between groups of cows treated with the long or short pour-on application, respectively. Plasma concentration of fluazuron at second and third application was increased (3.3 and 2.9 times, respectively) in calves under free suckling compared to cows. Nevertheless, both groups of cows and calves showed a significant increase in plasma concentration of fluazuron between times (4.9 times, p < 0.0001 and 2.8 times, p < 0.0001, respectively). In both groups, tick prevalence was 0% throughout the trial, except for day 77, which reached 1%. CONCLUSIONS: The main conclusions of this study were the following: 1) Different administration patterns (long vs. short) did not differ in plasma levels of fluazuron.; 2) Given that only the cows were treated and lactating calves presented higher plasma levels of fluazuron than cows, passage through milk appears to be relevant and possibly due to a cumulative effect and continuous drug intake.

Therapeutic equivalence of ivermectin 1% and two novel formulations combined of ivermectin 1% + fluazuron 12.5% for the control of Rhipicephalus (Boophilus) microplus in beef cattle from Uruguay.

Background: Novel combinations of ivermectin (IVM) and fluazuron (FLU) are presented as an alternative for the control of ticks in cattle. Applying a combination of drugs with the aim to affect different stages of the parasite's life cycle is established as a potential measure to achieve the control of ticks in cattle. Aim: To determine the therapeutic equivalence between two novel formulations of IVM 1% combined with FLU 12.5% tested on bovines naturally infested with Rhipicephalus (Boophilus) microplus. Methods: Forty adult beef cattle were randomized into four groups (n = 10): IVM [1% (0.2 mg/kg)], combinations groups A and B [IVM 1% (0.2 mg/kg) + FLU 12.5% (2.5 mg/kg), each], and control [untreated]). On days 14, 27, and 49 after administration, the presence of ticks was ranked as null, low, medium, and high; a cumulative link model was adjusted to evaluate treatment response. Results: Although all groups had some animals with the presence of ticks until day 27, on day 14 IVM [odds ratios (OR) 0.013, CI95%: 0.001-0.014, p < 0.01], A (OR 0.01, CI95%: 0.00-0.07, p < 0.01) and B (OR 0.01, CI95%: 0.00-0.148, p < 0.01) groups were different when compared to the control group, unlike on day 27 where only groups A (OR 0.02, CI95%: 0.00-0.17, p < 0.01) and B (OR 0.06, CI95%: 0.00-0.46, p < 0.01) remained different from the control group. On day 49 post-administration, IVM and B did not differ from the control group, with 0.95 probability (CI95% 0.92-1.02) of high parasite burden. At day 49 post-administration, group A was the only group free of ticks (OR 0.01, CI95%: 0.00-0.13, p < 0.01). Conclusions: Pharmacotechnical differences in combined formulations should be considered in therapeutic equivalence studies.

Pharmacokinetic study of oral amitriptyline in horses.

The purpose of this study was to evaluate the pharmacokinetics of oral amitriptyline in horses. Oral amitriptyline (1 mg/kg) was administered to six horses. Blood samples were collected from jugular and lateral thoracic vein at predetermined times from 0 to 24 hr after administration. Plasma concentrations were determined by high-performance liquid chromatography and analyzed using noncompartmental methods. Pharmacodynamic parameters including heart rate, respiration rate, and intestinal motility were evaluated, and electrocardiographic examinations were performed in all subjects. The mean maximum plasma concentration (Cmax ) of amitriptyline was 30.7 ng/ml, time to maximum plasma concentration (Tmax ) 1-2 hr, elimination half-life (t1/2 ) 17.2 hr, area under plasma concentration-time curve (AUC) 487.4 ng ml-1  hr-1 , apparent clearance (Cl/F) 2.6 L hr-1  kg-1 , and apparent volume of distribution (Vd/F) 60.1 L/kg. Jugular vein sampling overestimated the amount of amitriptyline absorbed and should not be used to study uptake following oral administration. Heart rate and intestinal motility showed significant variation (p < .05). Electrocardiography did not provide conclusive results. Further studies are required to discern if multiple dose treatment would take the drug to steady state as expected, consequently increasing plasma concentrations.

Role of CYP2C9, CYP2C19 and EPHX Polymorphism in the Pharmacokinetic of Phenytoin: A Study on Uruguayan Caucasian Subjects.

Phenytoin (PHT) oxidative route leads to its main metabolite p-hydroxyphenytoin (p-HPPH), by means of CYP2C9 and CYP2C19. Formation of p-HPPH proceeds via a reactive arene-oxide intermediate. This intermediate can also be converted into PHT dihydrodiol by microsomal epoxide hydrolase (EPHX). The three enzymes are polymorphically expressed and the genetic variants are responsible for changes in the enzyme activity. In order to evaluate the effect that these polymorphisms have on PHT metabolism, PHT and p-HPPH plasma concentrations were measured and the genotype for the three enzymes was assessed in 50 Uruguayan epileptic patients. 30% of the patients were intermediate and 2% were poor metabolizers for CYP2C9, while 20% were intermediate metabolizers for CYP2C19. 44%, 10%, and 46% of subjects had intermediate, increased and decreased activities of EPHX respectively. CYP2C9 was confirmed to be the main responsible enzyme for PHT biotransformation. CYP2C19 seemed to be preponderant in p-HPPH oxidative metabolism. Apart from being responsible for the production of the dihydrodiol metabolite, EPHX also seemed to contribute to pHPPH formation when its activity is low. PHT might be recovered with a decreased activity of EPHX regardless the activity of CYP2C9.

Chronic administration of phenytoin induces efflux transporter overexpression in rats.

BACKGROUND: Efflux transporters overexpression has been proposed as one of the responsible mechanism for refractory epilepsy by preventing access of the antiepileptic drug to the brain. In this work we investigated whether phenytoin (PHT), could induce efflux transporters overexpression, at different biological barriers and to evaluate the implication it could have on its pharmacokinetics and therapeutic/toxic response. METHODS: Forty-two adult females Sprague Dawley divided in five groups were treated with oral doses of 25, 50 and 75mg/kg/6h of PHT for 3 days and two additionally groups were treated with intraperitoneal (ip) doses of 25mg/kg/6h or 100mg/kg/24h. At day 4 PHT plasma concentrations were measured and, obtained several organs, brain, parotid gland, liver and duodenum in which were analyzed for the Pgp expression. At day 4 PHT plasma concentrations were measured and several tissues: brain, parotid gland, liver and duodenum were obtained in order to analyze Pgp expression. In order to evaluate the oral bioavailability of PHT, two groups were administered with oral or intraperitoneal doses of 100mg/kg and plasma level were measured. RESULTS: An induction of the expression of efflux transporter mediated by phenytoin in a concentration-and-time dependent manner was found when increasing oral and ip doses of phenytoin, One week after the interruption of ip treatment a basal expression of transporters was recovered. CONCLUSIONS: Overexpression of efflux transporters can be mediated by inducer agents like PHT in a local-concentration dependent manner, and it is reversible once the substance is removed from the body. The recovery of basal Pgp expression could allow the design of dosing schedules that optimize anticonvulsant therapy.

Antiepileptic drugs: Energy-consuming processes governing drug disposition.

Diffusion is not the main process by which drugs are disposed throughout the body. Translational movements of solutes given by different energy-consuming mechanisms are required in order to dispose them efficiently. Membrane transportation and cardiac output distribution are two effective processes to move the molecules among different body sites. Gastrointestinal-blood cycling constitutes a supplementary way to regulate the distribution of molecules between the non-hepatic organs and the liver. Any change in the relative supply of drug molecules among eliminating organs could modify their clearance from the body. Either the nonlinear phenytoin (PHT) pharmacokinetic response or the influence that carbamazepine (CBZ) exerts on PHT exposure could be explained throughout their efflux transporter inducer abilities. Cardiac output distribution difference between the individuals might also explain the dual CBZ-over-PHT interaction response. Finally, valproic acid (VPA) pharmacokinetics can be understood by adding to these mechanisms of transportation its ability to cross the mitochondrial membrane of the hepatocyte.

Hyperammonemia associated with valproic acid concentrations.

Valproic acid, a branched short-chain fatty acid, has numerous action mechanisms which turn it into a broad spectrum anticonvulsant drug and make its use possible in some other pathologies such as bipolar disorder. It is extensively metabolized in liver, representing ß -oxidation in the mitochondria one of its main metabolic route (40%). Carnitine is responsible for its entry into the mitochondria as any other fatty acid. Long-term high-dose VPA therapy or acute VPA overdose induces carnitine depletion, resulting in high levels of ammonia in blood. As a high correlation between salivary valproic acid levels and plasma ultrafiltrate levels was found in humans, saliva becomes a promising monitoring fluid in order to study valproic acid pharmacokinetics and its toxic effect. Extended-release (twice daily) formulations of valproic acid or carnitine supplementation are the proposed two therapeutic strategies in order to reverse hyperammonemia.

Experiencia Uruguaya en Atención Farmacéutica activa en la comunidad / Uruguayan experience in community-wide active pharmaceutical care

Objetivo: realizar una actividad de difusión a la población sobre el uso racional de medicamentos, mediante la inserción de los estudiantes en el equipo de salud y analizar los datos farmacoterapéuticos obtenidos de esta actividad educativa. Métodos: en la vía pública se instaló una carpa de Atención Farmacéutica durante tres días donde participaron químicos farmacéuticos y médicos, quienes impartieron charlas sobre diferentes temas de salud preponderantes en la población uruguaya. Asimismo, los alumnos de Atención Farmacéutica, como parte de su formación práctica, participaron de esta actividad mediante la realización de entrevistas a los transeúntes, llenado de fichas de perfiles farmacoterapéuticos y de consumo de plantas medicinales, elaboradas para este fin, y la entrega de folletos informativos. A partir de las fichas farmacoterapéuticas se desarrolló un trabajo de investigación. Resultados: los alumnos del curso participaron de forma activa en el llenado de las fichas farmacoterapéuticas y mantuvieron una comunicación fluida con los asistentes a la carpa y con los profesionales de la salud. Se completaron 117 fichas farmacoterapéuticas (90 mujeres y 27 hombres). El 60 por ciento de los entrevistados consumía plantas medicinales. Sesenta personas recibían cuatro o más especialidades farmacéuticas. Las drogas antihipertensivas resultaron las más utilizadas. Veintitrés personas presentaban hipotiroidismo y dos personas de este grupo recibían litio para trastorno bipolar. Entre el grupo de mujeres: 18 tomaban ansiolíticos, 12 antidepresivos, 7 hipnóticos y 2 antisicóticos. Diecinueve personas manifestaron tener colesterol alto y 14 recibían medicación. Catorce presentaban artrosis y 10 estaban en tratamiento con analgésicos. Nueve personas presentaban gastritis, grupo este con un alto consumo de café y mate. Seis mujeres mayores de 50 años, declararon tener osteoporosis y solo tres recibían medicación a base de calcio y vitamina D. Conclusiones: la experiencia tuvo aceptación por el público y muestra una vez más la necesidad de la población de una educación sanitaria responsable(AU)

Objective: to conduct a health promotion activity for the population on the rational use of drugs, in which students participate with the rest of the health team and to analyze pharmacotherapeutic data collected in this educational activity. Methods: a pharmaceutical care tent was put up on a public area for three days where physicians and pharmacists participated, giving talks on various prevailing health issues that affect the Uruguayan population. Also, a number of pharmaceutical care students, as part of their practical training, participated in this activity by interviewing passers-by, filling out forms of pharmacotherapeutic profiles and of consumption of herbal medicines and giving people some information leaflets. A research study was carried out from the data collected in these pharmacotherapeutic forms. Results: the students actively participated in filling out the pharmacotherapeutic profiles and keeping fluent communication with the audience and with health professionals. One hundred and seventeen pharmacotherapeutic forms were completed (90 women and 27 men). Sixty percent of the interviewed people consumed herbal medicines. Sixty people received four or more medicines. Antihypertensive drugs were the most commonly used. Twenty three people had hypothyroidism and two people in this group were treated with lithium for bipolar disorder. In the female group 18 took anxiolytics, 12 antidepressants, 7 hypnotic drugs and 2 antipsychotic drugs. Nineteen people reported high cholesterol condition and 14 of them took medication. Fourteen had osteoarthritis and 10 were under painkiller treatment. Nine people had gastritis and this group showed high consumption rates of coffee and mate. Six women over 50 years old reported having osteoporosis and only 3 of them took calcium-based medication and vitamin D. Conclusions: the experience was well-accepted by the public and once again, the need for responsible health education of the population was demonstrated(AU)

Verapamil effect on phenytoin pharmacokinetics in rats.

Efflux transporter and enzyme overexpression can be induced by certain antiepileptic drugs. Phenytoin (PHT) is at the same time substrate and inducer of CYP2C isoenzymes and efflux carriers. Its inductive effect has been postulated to be concentration and time-dependent. Since verapamil (VPM) is a well known substrate and inhibitor of P-glycoprotein, its administration could modify PHT systemic exposure. The objective of this work was to determine if single doses (40mg/kg) of VPM might change PHT body fate in the same way when given at the beginning or several days after 100mg/kg of PHT daily doses were started. Both drugs were administered intraperitoneally to female Sprague Dawley rats. VPM increased plasma PHT concentrations after one day of treatment, while a decrease in PHT plasma exposure was observed when VPM was added at the fifth day of the antiepileptic treatment. These results suggested that VPM would have different impact on PHT pharmacokinetics, depending on the level of expression of both efflux transporters and enzymes. Before the hepatic cells could acquire a high content of enzymes due to the inductive effect of PHT dosing, VPM decreased the predominant intestinal clearance of PHT. But, once the enzymatic machinery at the hepatocyte became more important than that at the intestine, although ineffective because of the high hepatobiliary efflux transporter overexpression, VPM blockade from the liver resulted in an increased total PHT clearance.