Falso positivo a morfina en orina por reactividad cruzada con alimemazina / False positive result to morphine in urine due to cross-reactivity to alimemazine

La alimemazina (Variargil(R)) es un antihistamínico anti-H1 reversible inespecífico que atraviesa la barrera hematoencefálica. Actúa como anticolinérgico. Su forma de presentación es en gotas en suspensión oral. Su uso clínico está extendido a rinitis alérgica estacional, angioedema y urticaria leve a partir de los 2 años de edad, conjuntivitis alérgica e insomnio de conciliación en la infancia. Presenta una farmacocinética muy variable, somnolencia excesiva conocida como «heavy hangover» y efecto de rebote tras su retirada. No está autorizado su uso en menores de 2 años. Presentamos el caso de un paciente de 19 meses que acude a Urgencias por referir somnolencia y falta de respuesta a estímulos tras la administración de alimemazina por dificultad para conciliar el sueño

Alimemazine (Variargil(R)) is a non-specific reversible anti-H1 antihistamine that crosses the blood-brain barrier. It acts as anticholinergic drug. It is marketed in drop form (oral suspension). It is used to relieve seasonal allergic rhinitis, angioedema, mild urticaria, allergic conjunctivitis, and for difficulty in falling asleep in children. It has a very variable pharmacokinetic, excessive "heavy hangover drowsiness" and rebound effect after withdrawal. It is not authorised for children under 2 years of age. The case is presented of a patient seen in the emergency room due to drowsiness and lack of response to stimuli after administration of alimemazine due to difficulties in falling asleep

Drop-to-drop solvent microextraction coupled with gas chromatography/mass spectrometry for rapid determination of trimeprazine in urine and blood of rats: application to pharmacokinetic studies.

A simple and rapid method based on drop-to-drop solvent microextraction (DDSME) coupled with gas chromatography/mass spectrometry (GC/MS) has been successfully applied for the pharmacokinetic studies of trimeprazine in 8 microL of urine and blood samples of rats. Several factors that influenced the extraction efficiency of DDSME, such as selection of organic solvent, extraction time, exposure volume of organic phase, addition of salt and pH, were optimized. Linearity was obtained over the concentration ranges of 0.2-10, 0.25-7.0 and 0.5-6.0 microg/mL with correlation coefficients of 0.998, 0.996 and 0.993 in deionized water, urine and blood samples of rats, respectively. The limits of detection (LODs) of trimeprazine were 0.05, 0.06 and 0.1 microg/mL in deionized water, urine and blood samples. The concentrations of trimeprazine obtained in urine and blood samples of rats were 0.21-1.25 and 2.72-0.22 microg/mL, respectively, after a single intravenous administration of this drug. The enrichment factors and LOD values obtained by DDSME coupled to GC/MS were compared with those of hollow fiber liquid-phase microextraction (HF-LPME) combined with GC/MS. We believe that this novel approach can be very useful in clinical application since only one microdrop of biological samples was required to perform the pharmacokinetic studies from rats, so the sample pretreatments for animal experiments can be very easy too.

Reversal of an antihistamine-induced coma with flumazenil.

Flumazenil is a competitive antagonist with specific action at the central benzodiazepine receptor. It is used when benzodiazepine intoxication is suspected. Its use has also been reported in cannabis intoxication, chloral hydrate overdose, hepatic encephalopathy, and alcohol intoxication. We report the case of a 7-month-old male infant with a depressed level of consciousness after intentional intoxication of antihistamines, whose mental status fully recovered after administration of flumazenil. To our knowledge, this is the first case in children where flumazenil has been reported to reverse antihistamine-induced coma.

Pharmacokinetics of trimeprazine in children.

The pharmacokinetics of trimeprazine (alimemazine) were studied over 24 hr in six children after a recommended preanaesthetic oral dose of 3 mg.kg-1. The degree of sedation before anaesthesia was evaluated. Median maximal venous blood drug concentration was 0.357 mumols.1(-1), 1-2 hr after oral ingestion, half-life 6.8 hr and AUC0-infinity h 2.758 mumols.1(-1) hr. Assuming 100 per cent bioavailability, blood clearance was estimated to median 3.7 1.kg-1.hr-1. Trimeprazine concentrations in cerebrospinal fluid (CSF) and in venous blood were compared in three other children, measured by gas chromatography. No trimeprazine was detected in the cerebrospinal fluid. We found a rough correlation between preanaesthetic sedation and blood trimeprazine concentrations. The kinetic parameters showed substantial interindividual differences, and accordingly, major interindividual variations in drug response might be anticipated even on standardized dosage regimens.