Extensión de tiempo QT
Efectos adversos de las drogas
Variantes ✨Para la evaluación computacionalmente intensiva de las variantes, elija la suscripción estándar paga.
Áreas de aplicación
Explicaciones para pacientes
Los cambios en la exposición mencionados se refieren a cambios en la curva de concentración plasmática-tiempo [AUC]. La exposición a alfentanilo aumenta al 995%, cuando se combina con eritromicina (266%) y fluconazol (356%). Esto puede provocar un aumento de los efectos secundarios. La exposición a eritromicina aumenta al 107%, cuando se combina con fluconazol (107%). Actualmente no podemos estimar la influencia de la alfentanilo. No esperamos ningún cambio en la exposición a fluconazol, cuando se combina con eritromicina (100%) y alfentanilo (100%).
Los parámetros farmacocinéticos de la población media se utilizan como punto de partida para calcular los cambios individuales en la exposición debidos a las interacciones.
La eritromicina tiene una baja biodisponibilidad oral [ F ] del 24%, por lo que el nivel plasmático máximo [Cmax] tiende a cambiar fuertemente con una interacción. La vida media terminal [ t12 ] es bastante corta a las 2.3 horas y se alcanzan rápidamente niveles plasmáticos constantes [ Css ]. La unión a proteínas [ Pb ] es moderadamente fuerte al 73% y el volumen de distribución [ Vd ] es de 56 litros, por eso, con una tasa de extracción hepática media de 0,9, tanto el flujo sanguíneo hepático [Q] como un cambio en la unión a proteínas [Pb] son relevantes. El metabolismo tiene lugar principalmente a través de CYP3A4. y el transporte activo se realiza en parte a través de MRP2 y PGP.
La alfentanilo tiene una biodisponibilidad oral media [ F ] del 41%, por lo que los niveles plasmáticos máximos [Cmax] tienden a cambiar con una interacción. La vida media terminal [ t12 ] es bastante corta a las 1.1 horas y se alcanzan rápidamente niveles plasmáticos constantes [ Css ]. La unión a proteínas [ Pb ] es moderadamente fuerte al 90% y el volumen de distribución [ Vd ] es de 36 litros en el rango medio. Dado que la sustancia tiene una tasa de extracción hepática baja de 0,9, el desplazamiento de la unión a proteínas [Pb] en el contexto de una interacción puede aumentar la exposición. El metabolismo tiene lugar principalmente a través de CYP3A4..
La fluconazol tiene una alta biodisponibilidad oral [ F ] del 90%, por lo que los niveles plasmáticos máximos [Cmax] tienden a cambiar poco durante una interacción. La vida media terminal [ t12 ] es bastante larga a las 30 horas y los niveles plasmáticos constantes [ Css ] solo se alcanzan después de más de 120 horas. La unión a proteínas [ Pb ] es muy débil al 11.5% y el volumen de distribución [ Vd ] es de 56 litros. Aproximadamente el 80.0% de la dosis administrada se excreta inalterada a través de los riñones y esta proporción rara vez se modifica por las interacciones. El metabolismo no tiene lugar a través de los citocromos comunes..
|Efectos serotoninérgicos a||1||Ø||+||Ø|
Recomendación: Como medida de precaución, se deben tener en cuenta los síntomas de la sobreestimulación serotoninérgica, especialmente después de un aumento de la dosis y a dosis en el rango terapéutico superior.
Clasificación: La alfentanilo tiene un efecto leve sobre el sistema serotoninérgico. El riesgo de un síndrome serotoninérgico se puede clasificar como bajo con este medicamento si la dosis está en el rango habitual. Según nuestro conocimiento, ni la eritromicina ni la fluconazol aumentan la actividad serotoninérgica.
Clasificación: Según nuestros hallazgos, ni la eritromicina, alfentanilo ni la fluconazol aumentan la actividad anticolinérgica.
Extensión de tiempo QT
Clasificación: En combinación, la eritromicina y la fluconazol pueden desencadenar potencialmente arritmias ventriculares del tipo torsades de pointes. No conocemos ningún potencial de prolongación del intervalo QT para la alfentanilo.
Efectos secundarios generales
|Efectos secundarios||∑ frecuencia||eri||alf||flu|
|Dolor de cabeza||7.4 %||n.a.||n.a.||7.5|
|Depresion respiratoria||2.0 %||n.a.||2.0↑||n.a.|
|Dolor abdominal||1.0 %||+||n.a.||n.a.|
Pérdida de apetito: eritromicina
Diarrea por clostridium difficile: eritromicina
Fosfatasa alcalina elevada: fluconazol
ALT elevado: fluconazol
AST elevado: fluconazol
Hepatitis colestásica: eritromicina
Insuficiencia hepática: eritromicina, fluconazol
Reacción de hipersensibilidad: alfentanilo
Reacciones alérgicas de la piel: eritromicina
Síndrome de DRESS: fluconazol
Espasmo laríngeo: alfentanilo
Pérdida de la audición: eritromicina
Arritmia ventricular: eritromicina
Síndrome de Stevens-Johnson: eritromicina, fluconazol
Necrolisis epidérmica toxica: eritromicina, fluconazol
Incautación: eritromicina, fluconazol, alfentanilo
Presión intracraneal elevada: alfentanilo
Nefritis tubulointersticial: eritromicina
Con base en sus
Referencias de literatura
Abstract: No Abstract available
Abstract: 1. The oral pharmacokinetics of fluconazole were studied in three groups of volunteers (n = 5) with various degrees of renal function (GFR greater than 70 ml min-1; 20-70 ml min-1; less than 20 ml min-1) and in a group of patients with chronic end-stage renal failure requiring regular haemodialysis. 2. The pharmacokinetics of fluconazole were markedly affected by impaired renal function with the elimination of half-life in Group III (GFR less than 20 ml min-1) being approximately three times that observed in normal volunteers (Group I). 3. Fluconazole renal clearance was positively correlated with GFR. 4. Non-renal clearance of fluconazole decreased with decreasing renal function. 5. Approximately 38% of the 50 mg dose of fluconazole was removed by haemodialysis extending over a 3 h period.
Abstract: No Abstract available
Abstract: No Abstract available
Abstract: Erythromycin is a widely used antibiotic in today's armamentarium of antibiotics. Although erythromycin induced ventricular tachyarrhythmia is rare, this potentially life-threatening reaction should be kept in mind. The relative rarity of 'torsades de pointes' arrhythmia suggests that other predisposing factors contribute to the acquired long QT syndrome. Since more and more macrolide products have been approved by the Food and Drug Administration for use in the United States, the potential problem with 'torsades de pointes' may exist with each of the macrolide antibiotic. Until the exact mechanisms of the arrhythmia are worked out, close monitoring of rhythms and QT intervals of high risk patients who require erythromycin is certainly advisable. Only a heightened awareness among the physicians and medical personnel can the adverse outcome be minimized.
Abstract: To determine the role of acid hydrolysis on the gastrointestinal absorption of erythromycin, six healthy subjects received erythromycin as a 240 mg intravenous dose, a 250 mg oral solution administered via endoscope directly into the duodenum and bypassing the stomach, and an enteric-coated 250 mg capsule. Blood samples were collected for 6 hours and serum erythromycin quantified by a microbiological method. The time to achieve maximum serum concentrations for the solution was 0.25 +/- 0.08 (mean +/- SD) hours and for the capsule was 2.92 +/- 0.55 hours. The absolute bioavailability of erythromycin from the capsule was 32 +/- 7% and for the duodenal solution 43 +/- 14%. The ratio of the areas under the serum erythromycin concentration-time curve of capsule to solution was 80 +/- 28% (range 38 to 110%). There is substantial loss of erythromycin apart from gastric acid hydrolysis, which cannot be accounted for by hepatic first-pass metabolism. Attempts to further improve the oral bioavailability of erythromycin beyond 50% by manipulation of formulation are likely to be futile.
Abstract: A 25-year-old woman who was hospitalized for worsening endocarditis had a prolonged QT interval at baseline and developed monomorphic ventricular arrhythmias, which were managed successfully with pacing and antiarrhythmic therapy. Several days later, the patient started receiving high-dose fluconazole for fungemia and subsequently experienced episodes of torsades de pointes, a polymorphic ventricular arrhythmia associated with a prolonged QT interval or prominent U wave on the electrocardiogram. The arrhythmia developed in the presence of known risk factors. Clinicians should be aware of these risk factors and other relevant structural similarities with drugs that cause torsades de pointes so that they can recognize patients who may be at risk for fluconazole-associated arrhythmia.
Abstract: The synthetic opioid alfentanil is an analgesic and an in vivo probe for hepatic and first-pass CYP3A activity. Alfentanil is a particularly useful CYP3A probe because pupil diameter change is a surrogate for plasma concentrations, thereby affording noninvasive assessment of CYP3A. Alfentanil undergoes extensive CYP3A4 metabolism via two major pathways, forming noralfentanil and N-phenylpropionamide. This investigation evaluated alfentanil metabolism in vitro to noralfentanil and N-phenylpropionamide, by expressed CYP3A5 and CYP3A7 in addition to CYP3A4, with and without coexpressed or exogenous cytochrome b(5). Effects of the CYP3A inhibitors troleandomycin and ketoconazole were also determined. Rates of noralfentanil and N-phenylpropionamide formation by CYP3A4 and 3A5 in the absence of b(5) were generally equivalent, although the metabolite formation ratio differed, whereas those by CYP3A7 were substantially less. CYP3A4 and 3A5 were equipotently inhibited by troleandomycin, whereas ketoconazole was an order of magnitude more potent toward CYP3A4. Cytochrome b(5) qualitatively and quantitatively altered alfentanil metabolism, with b(5) coexpression having a greater effect than exogenous addition. Addition or coexpression of b(5) markedly stimulated the formation of both metabolites and changed the formation of noralfentanil but not N-phenylpropionamide from apparent single-site to multisite Michaelis-Menten kinetics. These results demonstrate that alfentanil is a substrate for CYP3A5 in addition to CYP3A4, and the effects of the CYP3A inhibitors troleandomycin and ketoconazole are CYP3A enzyme-selective. Alfentanil is one of the few CYP3A substrates that is metabolized in vitro as avidly by both CYP3A4 and 3A5. Polymorphic CYP3A5 expression may contribute to inter-individual variability in alfentanil metabolism.
Abstract: This investigation determined the ability of alfentanil miosis and single-point concentrations to detect various degrees of CYP3A inhibition. Results were compared with those for midazolam, an alternative CYP3A probe. Twelve volunteers were studied in a randomized 4-way crossover, targeting 12%, 25%, and 50% inhibition of hepatic CYP3A. They received 0, 100, 200, or 400 mg oral fluconazole, followed 1 hour later by 1 mg intravenous midazolam and then 15 microg/kg intravenous alfentanil 1 hour later. The next day, they received fluconazole, followed by 3 mg oral midazolam and 40 microg/kg oral alfentanil. Dark-adapted pupil diameters were measured coincident with blood sampling. Area under the plasma concentration-time curve (AUC) ratios (fluconazole/control) after 100, 200, and 400 mg fluconazole were (geometric mean) 1.3*, 1.4*, and 2.0* for intravenous midazolam and 1.2*, 1.6*, and 2.2* for intravenous alfentanil (*significantly different from control), indicating 16% to 21%, 31% to 36%, and 43% to 53% inhibition of hepatic CYP3A. Single-point concentration ratios were 1.5*, 1.8*, and 2.4* for intravenous midazolam (at 5 hours) and 1.2*, 1.6*, and 2.2* for intravenous alfentanil (at 4 hours). Pupil miosis AUC ratios were 0.9, 1.0, and 1.2*. After oral dosing, plasma AUC ratios were 2.3*, 3.6*, and 5.3* for midazolam and 1.8*, 2.9*, and 4.9* for alfentanil; plasma single-point ratios were 2.4*, 4.5*, and 6.9* for midazolam and 1.8*, 2.9*, and 4.9* for alfentanil, and alfentanil miosis ratios were 1.1, 1.9*, and 2.7*. Plasma concentration AUC ratios of alfentanil and midazolam were equivalent for detecting hepatic and first-pass CYP3A inhibition. Single-point concentrations were an acceptable surrogate for formal AUC determinations and as sensitive as AUCs for detecting CYP3A inhibition. Alfentanil miosis could detect 50% to 70% inhibition of CYP3A activity, but was less sensitive than plasma AUCs. Further refinements are needed to increase the sensitivity of alfentanil miosis for detecting small CYP3A changes.
Abstract: OBJECTIVE: Alfentanil is a short-acting synthetic opioid analgesic, which is extensively metabolized, mainly by hepatic cytochrome P450 (CYP) 3A enzymes. Concomitant administration of alfentanil and CYP3A inhibitors may lead to clinically important drug interactions. We investigated the possible interactions between alfentanil and orally administered voriconazole and terbinafine. METHODS: A randomized crossover study design in 3 phases was used. Twelve healthy volunteers were given 20 microg/kg intravenous alfentanil without pretreatment (control), after oral voriconazole administration (400 mg twice on the first day and 200 mg twice on the second day), or after oral terbinafine administration (250 mg once daily for 3 days). Plasma concentrations of alfentanil were measured for 10 hours, and the pharmacokinetic parameters were calculated by use of noncompartmental methods. RESULTS: Voriconazole decreased the mean plasma clearance of intravenous alfentanil by 85%, from the control value of 4.4+/-2.4 mL.min-1.kg-1 to 0.67+/-0.27 mL.min-1.kg-1 (P<.001), and prolonged its elimination half-life from 1.5+/-0.49 hours to 6.6+/-1.8 hours (P<.001). The area under the alfentanil plasma concentration-time curve was increased by 6-fold by voriconazole (P<.001). Terbinafine had no statistically significant effect on the pharmacokinetics of alfentanil. Alfentanil administration caused nausea in 5 volunteers and vomiting in 2. These side effects all occurred in volunteers in the voriconazole phase. CONCLUSION: Oral voriconazole, but not terbinafine, markedly inhibited the metabolism of alfentanil. Caution should be exercised when alfentanil is given to patients receiving voriconazole. It is reasonable to assume that patients receiving voriconazole require 70% to 90% less alfentanil for the maintenance of analgesia than patients who are not receiving concomitant CYP3A inhibitors.
Abstract: The hepatic and first-pass cytochrome P4503A (CYP3A) probe alfentanil (ALF) is also metabolized in vitro by CYP3A5. Human hepatic microsomal ALF metabolism is higher in livers with at least one CYP3A5*1 allele and higher CYP3A5 protein content, compared with CYP3A5*3 homozygotes with little CYP3A5. The influence of CYP3A5 genotype on ALF pharmacokinetics and pharmacodynamics was studied, and compared to midazolam (MDZ), another CYP3A probe. Healthy volunteers (58 men, 41 women) were genotyped for CYP3A5 *1, *3, *6, and *7 alleles. They received intravenous MDZ then ALF, and oral MDZ and ALF the next day. Plasma MDZ and ALF concentrations were determined by mass spectrometry. Dark-adapted pupil diameters were determined coincident with blood sampling. In CYP3A5(*)3/(*)3 (n=62), (*)1/(*)3 (n=28), and (*)1/(*)1 (n=8) genotypes, systemic clearances of ALF were 4.6+/-1.8, 4.8+/-1.7, and 3.9+/-1.7 ml/kg/min and those of MDZ were 7.8+/-2.3, 7.7+/-2.3, and 6.0+/-1.4 ml/kg/min, respectively (not significant), and apparent oral clearances were 11.8+/-7.2, 13.3+/-6.1, and 12.6+/-8.2 ml/kg/min for ALF and 35.2+/-19.0, 36.4+/-15.7, and 29.4+/-9.3 ml/kg/min for MDZ (not significant). Clearances were not different between African Americans (n=25) and Whites (n=68), or between CYP3A5 genotypes within African Americans. ALF pharmacodynamics was not different between CYP3A5 genotypes. There was consistent concordance between ALF and MDZ, in clearances and extraction ratios. Thus, in a relatively large cohort of healthy subjects with constitutive CYP3A activity, CYP3A5 genotype had no effect on the systemic or apparent oral clearances, or pharmacodynamics, of the CYP3A probes ALF and MDZ, despite affecting their hepatic microsomal metabolism.
Abstract: The numbers of patients dying with end-stage renal disease (ESRD), particularly those managed conservatively (without dialysis) or withdrawing from dialysis is increasing rapidly in developed countries. There is growing awareness of the extensive symptom control needs of these patients. Pain is a common problem, and has been both under-recognized and under-treated. It is challenging to manage, largely because of the constraints very poor renal function places on use of medication. Although pharmacological reviews of opioid use in renal failure have been published, there is a need for clinical recommendations to aid palliative and renal specialists in providing effective pain control. This review describes the pharmacological evidence for and against the use of the different opioid medications, and translates this into clinical recommendations for ESRD patients managed conservatively, not for those on dialysis for whom there are different pharmacological considerations. Acetaminophen (paracetamol) is recommended at Step 1 of the World Health Organization ladder. Of the Step 2 analgesics, tramadol is the least problematic, although dose reduction and increased dosing interval are required, and caution should be exercised. Of the Step 3 analgesics, fentanyl, alfentanil and methadone are recommended. There is limited evidence for buprenorphine, although theoretical reasons why it may be a good choice for these patients. Hydromorphone and oxycodone cannot be recommended because of extremely limited evidence, although each is likely a better choice than morphine or diamorphine. Morphine and diamorphine themselves are not recommended because of known accumulation of potentially toxic metabolites.
Abstract: Fluconazole is an antifungal medication that has been reported to cause prolongation of the QT interval and Torsades de Pointes (TdP) ventricular tachycardia in adults. We describe the case of an 11-year-old child treated with fluconazole who developed ventricular arrhythmia culminating in TdP. We discuss the possible roles played by genetic and environmental factors in this child's rhythm disturbances. After briefly summarizing similar cases from the adult literature, we outline the putative mechanism by which fluconazole may cause arrhythmia. This case should alert pediatricians to the possible risks of fluconazole use, especially in the presence of electrolyte abnormalities, diuretic use, therapy with other pro-arrhythmic agents, or suspicion of congenital Long-QT Syndrome.
Abstract: PURPOSE: A case of torsades de pointes associated with fluconazole use is described. SUMMARY: A 68-year-old woman with a history of hypertension treated with 2.5 mg of indapamide for 16 months sought medical treatment after having two falls 1 month apart. A computed tomography scan and subsequent magnetic resonance imaging of the brain revealed a lesion in the left pons and middle cerebellar peduncle. Biopsy of the pontine lesion revealed large yeast forms and subsequently revealed Cryptococcus neoformans var. gattii. The patient was initially treated with conventional amphotericin B and flucytosine for six weeks. The first week of therapy was complicated by hypokalemia, hypomagnesemia, and an episode of atrial fibrillation that was managed with electrolyte replacement, commencement of metoprolol, and switching from conventional amphotericin B to amphotericin B lipid complex. After six weeks, liposomal amphotericin was discontinued and high-dose oral fluconazole was initiated. Six days after beginning fluconazole therapy, the patient had a generalized tonic-clonic seizure and suffered cardiopulmonary arrest. Postresuscitation, an electrocardiogram demonstrated a corrected Q-T interval of 556 msec. Recurrent episodes of torsades de pointes were also recorded postarrest. Fluconazole was discontinued at this time, and liposomal amphotericin B was resumed. Neurologic and electroencephalographic assessment conducted 48 hours postarrest revealed that significant neurologic damage had been sustained. Supportive care was withdrawn, and the patient died two days later. A postmortem examination revealed no coronary artery disease or hemorrhagic transformation of the pontine cryptococcoma. CONCLUSION: Treatment with high-dose fluconazole was the probable cause of torsades de pointes in a patient with risk factors for this condition. The benefits and risks of using fluconazole should be carefully weighed for patients with risk factors for Q-T interval prolongation.
Abstract: BACKGROUND: Methadone clearance is highly variable, and drug interactions are problematic. Both have been attributed to CYP3A, but actual mechanisms are unknown. Drug interactions can provide such mechanistic information. Ritonavir/indinavir, one of the earliest protease inhibitor combinations, may inhibit CYP3A. We assessed ritonavir/indinavir effects on methadone pharmacokinetics and pharmacodynamics, intestinal and hepatic CYP3A activity, and intestinal transporters (P-glycoprotein) activity. CYP3A and transporters were assessed with alfentanil and fexofenadine, respectively. METHODS: Twelve healthy human immunodeficiency virus-negative volunteers underwent a sequential three-part crossover. On three consecutive days, they received oral alfentanil/fexofenadine, intravenous alfentanil, and intravenous plus oral (deuterium-labeled) methadone, repeated after acute (3 days) and steady-state (2 weeks) ritonavir/indinavir. Plasma and urine analytes were measured by mass spectrometry. Opioid effects were assessed by miosis. RESULTS: Alfentanil apparent oral clearance was inhibited more than 97% by both acute and steady-state ritonavir/indinavir, and systemic clearance was inhibited more than 90% due to diminished hepatic and intestinal extraction. Ritonavir/indinavir increased fexofenadine area under the plasma concentration-time curve four- to five-fold, suggesting significant inhibition of gastrointestinal P-glycoprotein. Ritonavir/indinavir slightly increased methadone N-demethylation, but it had no significant effects on methadone plasma concentrations or on systemic or apparent oral clearance, renal clearance, hepatic extraction or clearance, or bioavailability. Ritonavir/indinavir had no significant effects on methadone plasma concentration-effect relationships. CONCLUSIONS: Inhibition of both hepatic and intestinal CYP3A activity is responsible for ritonavir/indinavir drug interactions. Methadone disposition was unchanged, despite profound inhibition of CYP3A activity, suggesting little or no role for CYP3A in clinical methadone metabolism and clearance. Methadone bioavailability was unchanged, despite inhibition of gastrointestinal P-glycoprotein activity, suggesting that this transporter does not limit methadone intestinal absorption.
Abstract: BACKGROUND: Methadone plasma concentrations are decreased by nelfinavir. Methadone clearance and the drug interactions have been attributed to CYP3A4, but actual mechanisms of methadone clearance and the nelfinavir interaction are unknown. We assessed nelfinavir effects on methadone pharmacokinetics and pharmacodynamics, intestinal and hepatic CYP3A4/5 activity, and intestinal P-glycoprotein transport activity. CYP3A4/5 and transporters were assessed using alfentanil and fexofenadine, respectively. METHODS: Twelve healthy HIV-negative volunteers underwent a sequential crossover. On three consecutive days they received oral alfentanil plus fexofenadine, intravenous alfentanil, and intravenous plus oral methadone. This was repeated after nelfinavir. Plasma and urine analytes were measured by mass spectrometry. Opioid effects were measured by pupil diameter change (miosis). RESULTS: Nelfinavir decreased intravenous and oral methadone plasma concentrations 40-50%. Systemic clearance, hepatic clearance, and hepatic extraction all increased 1.6- and 2-fold, respectively, for R- and S-methadone; apparent oral clearance increased 1.7- and 1.9-fold. Nelfinavir stereoselectively increased (S>R) methadone metabolism and metabolite formation clearance, and methadone renal clearance. Methadone bioavailability and P-glycoprotein activity were minimally affected. Nelfinavir decreased alfentanil systemic and apparent oral clearances 50 and 76%, respectively. Nelfinavir appeared to shift the methadone plasma concentration-effect (miosis) curve leftward and upward. CONCLUSIONS: Nelfinavir induced methadone clearance by increasing renal clearance, and more so by stereoselectively increasing hepatic metabolism, extraction and clearance. Induction occurred despite 50% inhibition of hepatic CYP3A4/5 activity and more than 75% inhibition of first-pass CYP3A4/5 activity, suggesting little or no role for CYP3A in clinical methadone disposition. Nelfinavir may alter methadone pharmacodynamics, increasing clinical effects.
Abstract: Nonrenal clearance of drugs can be significantly lower in patients with end-stage renal disease (ESRD) than in those with normal renal function. Using erythromycin (ER) as a probe compound, we investigated whether this decrease in nonrenal clearance is due to reduced hepatic clearance (CL(H)) and/or gut metabolism. We also examined the potential effects of the uremic toxins 3-carboxy-4-methyl-5-propyl-2-furan propanoic acid (CMPF) and indoxyl sulfate (Indox) on ER disposition. Route-randomized, two-way crossover pharmacokinetic studies of ER were conducted in 12 ESRD patients and 12 healthy controls after oral (250 mg) and intravenous (125 mg) dosing with ER. In patients with ESRD, CL(H) decreased 31% relative to baseline values (0.35 +/- 0.14 l/h/kg vs. 0.51 +/- 0.13 l/h/kg, P = 0.01), with no change in steady-state volume of distribution. With oral dosing, the bioavailability of ER increased 36% in patients with ESRD, and this increase was not related to changes in gut availability. As expected, plasma levels of CMPF and Indox were significantly higher in the patients than in the healthy controls. However, no correlation was observed between CL(H) of ER and the levels of uremic toxins.
Abstract: The macrolide antiobiotic erythromycin undergoes extensive hepatic metabolism and is commonly used as a probe for cytochrome P450 (CYP) 3A4 activity. By means of a transporter screen, erythromycin was identified as a substrate for the transporter ABCC2 (MRP2) and its murine ortholog, Abcc2. Because these proteins are highly expressed on the biliary surface of hepatocytes, we hypothesized that impaired Abcc2 function may influence the rate of hepatobiliary excretion and thereby enhance erythromycin metabolism. Using Abcc2 knockout mice, we found that Abcc2 deficiency was associated with a significant increase in erythromycin metabolism, whereas murine Cyp3a protein expression and microsomal Cyp3a activity were not affected. Next, in a cohort of 108 human subjects, we observed that homozygosity for a common reduced-function variant in ABCC2 (rs717620) was also linked to an increase in erythromycin metabolism but was not correlated with the clearance of midazolam. These results suggest that impaired ABCC2 function can alter erythromycin metabolism, independent of changes in CYP3A4 activity.
Abstract: BACKGROUND: Opioid use in patients with renal impairment can lead to increased adverse effects. Opioids differ in their effect in renal impairment in both efficacy and tolerability. This systematic literature review forms the basis of guidelines for opioid use in renal impairment and cancer pain as part of the European Palliative Care Research Collaborative's opioid guidelines project. OBJECTIVE: The objective of this study was to identify and assess the quality of evidence for the safe and effective use of opioids for the relief of cancer pain in patients with renal impairment and to produce guidelines. SEARCH STRATEGY: The Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, MedLine, EMBASE and CINAHL were systematically searched in addition to hand searching of relevant journals. SELECTION CRITERIA: Studies were included if they reported a clinical outcome relevant to the use of selected opioids in cancer-related pain and renal impairment. The selected opioids were morphine, diamorphine, codeine, dextropropoxyphene, dihydrocodeine, oxycodone, hydromorphone, buprenorphine, tramadol, alfentanil, fentanyl, sufentanil, remifentanil, pethidine and methadone. No direct comparator was required for inclusion. Studies assessing the long-term efficacy of opioids during dialysis were excluded. DATA COLLECTION AND ANALYSIS: This is a narrative systematic review and no meta-analysis was performed. The Grading of RECOMMENDATIONS Assessment, Development and Evaluation (GRADE) approach was used to assess the quality of the studies and to formulate guidelines. MAIN RESULTS: Fifteen original articles were identified. Eight prospective and seven retrospective clinical studies were identified but no randomized controlled trials. No results were found for diamorphine, codeine, dihydrocodeine, buprenorphine, tramadol, dextropropoxyphene, methadone or remifentanil. CONCLUSIONS: All of the studies identified have a significant risk of bias inherent in the study methodology and there is additional significant risk of publication bias. Overall evidence is of very low quality. The direct clinical evidence in cancer-related pain and renal impairment is insufficient to allow formulation of guidelines but is suggestive of significant differences in risk between opioids. RECOMMENDATIONS: RECOMMENDATIONS regarding opioid use in renal impairment and cancer pain are made on the basis of pharmacokinetic data, extrapolation from non-cancer pain studies and from clinical experience. The risk of opioid use in renal impairment is stratified according to the activity of opioid metabolites, potential for accumulation and reports of successful or harmful use. Fentanyl, alfentanil and methadone are identified, with caveats, as the least likely to cause harm when used appropriately. Morphine may be associated with toxicity in patients with renal impairment. Unwanted side effects with morphine may be satisfactorily dealt with by either increasing the dosing interval or reducing the 24 hour dose or by switching to an alternative opioid.
Abstract: Mechanisms by which efavirenz diminishes methadone plasma concentrations are unknown. This investigation determined efavirenz influence on clinical methadone disposition and miosis, intravenous and oral alfentanil clearance (hepatic and intestinal cytochrome P450 3A4/5 (CYP3A4/5) activity), fexofenadine disposition (intestinal transporters activity), and efavirenz clearance and 8-hydroxylation (CYP2B6 activity), and human hepatocyte effects. Efavirenz induced systemic and oral alfentanil clearances two- to fivefold and induced efavirenz 8-hydroxylation. Efavirenz stereoselectively decreased methadone plasma concentrations 50-70%. Methadone systemic and oral clearances, hepatic clearance and extraction ratio, N-demethylation, and metabolite formation clearance were stereoselectively increased two- to threefold. Bioavailability decreased. Efavirenz shifted methadone concentration-miosis curves leftward and upward. Efavirenz induced hepatocyte CYP2B6 and CYP3A4 expression, activity, and methadone N-demethylation. Results show that efavirenz coinduced hepatic CYP2B6 and CYP3A4/5, coinduced hepatic and intestinal CYP3A4/5, and coinduced gastrointestinal CYP3A4/5 and efflux transporters. Methadone disposition was most consistent with efavirenz induction of hepatic CYP2B6-mediated methadone N-demethylation. Efavirenz may alter methadone pharmacodynamics.
Abstract: Transporters in proximal renal tubules contribute to the disposition of numerous drugs. Furthermore, the molecular mechanisms of tubular secretion have been progressively elucidated during the past decades. Organic anions tend to be secreted by the transport proteins OAT1, OAT3 and OATP4C1 on the basolateral side of tubular cells, and multidrug resistance protein (MRP) 2, MRP4, OATP1A2 and breast cancer resistance protein (BCRP) on the apical side. Organic cations are secreted by organic cation transporter (OCT) 2 on the basolateral side, and multidrug and toxic compound extrusion (MATE) proteins MATE1, MATE2/2-K, P-glycoprotein, organic cation and carnitine transporter (OCTN) 1 and OCTN2 on the apical side. Significant drug-drug interactions (DDIs) may affect any of these transporters, altering the clearance and, consequently, the efficacy and/or toxicity of substrate drugs. Interactions at the level of basolateral transporters typically decrease the clearance of the victim drug, causing higher systemic exposure. Interactions at the apical level can also lower drug clearance, but may be associated with higher renal toxicity, due to intracellular accumulation. Whereas the importance of glomerular filtration in drug disposition is largely appreciated among clinicians, DDIs involving renal transporters are less well recognized. This review summarizes current knowledge on the roles, quantitative importance and clinical relevance of these transporters in drug therapy. It proposes an approach based on substrate-inhibitor associations for predicting potential tubular-based DDIs and preventing their adverse consequences. We provide a comprehensive list of known drug interactions with renally-expressed transporters. While many of these interactions have limited clinical consequences, some involving high-risk drugs (e.g. methotrexate) definitely deserve the attention of prescribers.
Abstract: All pharmaceutical companies are required to assess pharmacokinetic drug-drug interactions (DDIs) of new chemical entities (NCEs) and mathematical prediction helps to select the best NCE candidate with regard to adverse effects resulting from a DDI before any costly clinical studies. Most current models assume that the liver is a homogeneous organ where the majority of the metabolism occurs. However, the circulatory system of the liver has a complex hierarchical geometry which distributes xenobiotics throughout the organ. Nevertheless, the lobule (liver unit), located at the end of each branch, is composed of many sinusoids where the blood flow can vary and therefore creates heterogeneity (e.g. drug concentration, enzyme level). A liver model was constructed by describing the geometry of a lobule, where the blood velocity increases toward the central vein, and by modeling the exchange mechanisms between the blood and hepatocytes. Moreover, the three major DDI mechanisms of metabolic enzymes; competitive inhibition, mechanism based inhibition and induction, were accounted for with an undefined number of drugs and/or enzymes. The liver model was incorporated into a physiological-based pharmacokinetic (PBPK) model and simulations produced, that in turn were compared to ten clinical results. The liver model generated a hierarchy of 5 sinusoidal levels and estimated a blood volume of 283 mL and a cell density of 193 × 106 cells/g in the liver. The overall PBPK model predicted the pharmacokinetics of midazolam and the magnitude of the clinical DDI with perpetrator drug(s) including spatial and temporal enzyme levels changes. The model presented herein may reduce costs and the use of laboratory animals and give the opportunity to explore different clinical scenarios, which reduce the risk of adverse events, prior to costly human clinical studies.
Abstract: According to current US Food and Drug Administration (FDA) and European Medicines Agency (EMA) guidance documents, physiologically based pharmacokinetic (PBPK) modeling is a powerful tool to explore and quantitatively predict drug-drug interactions (DDIs) and may offer an alternative to dedicated clinical trials. This study provides whole-body PBPK models of rifampicin, itraconazole, clarithromycin, midazolam, alfentanil, and digoxin within the Open Systems Pharmacology (OSP) Suite. All models were built independently, coupled using reported interaction parameters, and mutually evaluated to verify their predictive performance by simulating published clinical DDI studies. In total, 112 studies were used for model development and 57 studies for DDI prediction. 93% of the predicted area under the plasma concentration-time curve (AUC) ratios and 94% of the peak plasma concentration (C) ratios are within twofold of the observed values. This study lays a cornerstone for the qualification of the OSP platform with regard to reliable PBPK predictions of enzyme-mediated and transporter-mediated DDIs during model-informed drug development. All presented models are provided open-source and transparently documented.
Abstract: A biowaiver is accepted by the Brazilian Health Surveillance Agency (ANVISA) for immediate-release solid oral products containing Biopharmaceutics Classification System (BCS) class I drugs showing rapid drug dissolution. This study aimed to simulate plasma concentrations of fluconazole capsules with different dissolution profiles and run population simulation to evaluate their bioequivalence. The dissolution profiles of two batches of the reference product Zoltec150 mg capsules, A1 and A2, and two batches of other products (B1 and B2; C1 and C2), as well as plasma concentration-time data of the reference product from the literature, were used for the simulations. Although products C1 and C2 had drug dissolutions < 85% in 30 min at 0.1 M HCl, simulation results demonstrated that these products would show the same in vivo performance as products A1, A2, B1, and B2. Population simulation results of the ln-transformed 90% confidence interval for the ratio ofand AUCvalues for all products were within the 80-125% interval, showing to be bioequivalent. Thus, even though the in vitro dissolution behavior of products C1 and C2 was not equivalent to a rapid dissolution profile, the computer simulations proved to be an important tool to show the possibility of bioequivalence for these products.