Oral midazolam versus midazolam and meperidine in the pediatric patient.
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Adjuvants, Anesthesia↗
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[Flumazenil and respiratory depression induced by midazolam-fentanyl or midazolam-nalbuphine combinations].
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Adult↗
[Premedication before gastroscopy. Midazolam versus midazolam plus pentazocine].
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Adult↗
[A comparison between thiopental, midazolam-ketalar and midazolam-ketalar-aneksat for anesthesia during cesarean section].
The effect of dormicum-ketalar and dormicum-ketalar-anexat in comparison with thiopental was studied on 45 parturients at 39-40 weeks' pregnancy, operated electively, divided into three groups as each group consisted of 15 women. The representative groups were compared by the following parameters: duration of the operation, age, weight, duration of induction in anaesthesia-extraction of the fetus, premedication, anaesthesia after the extraction of the fetus. Usage of dormicum ketalar for induction in anaesthesia during cesarean section did not affect the basic metabolic parameters of the parturients, fetus and amniotic fluid. Such a combination of preparations during simultaneous neutralization of the action of dormicum by anexat affects positively the fetal state, transport of O2 and activity of enzymes, in order that the fetus could survive more favourably this critical state.
Anesthesia, Obstetrical↗
Midazolam and amplitude-integrated EEG in asphyxiated full-term neonates.
AIM: In the present, prospective study, the relation between the levels of midazolam, its two active metabolites--1-hydroxy-midazolam (OH-midazolam) and 1-hydroxy-midazolam-glucuronide (glu-midazolam)--and the aEEG were examined. PATIENTS AND METHODS: Fifteen full-term neonates with seizures due to hypoxic-ischaemic encephalopathy admitted to our NICU were included. Midazolam (loading dose 0.05 mg/kg in 10 min, maintenance dose 0.15 mg/kg/h) was used as an add-on anti-convulsant after phenobarbital and lidocaine because of continuing seizures. Amplitude-integrated EEG background pattern was scored at the start of midazolam and at the time of blood sampling as continuous normal voltage (CNV), discontinuous normal voltage (DNV), burst suppression (BS), continuous low voltage (CLV) or flat trace (FT). Serum levels of midazolam, OH-midazolam and glu-midazolam were measured at least 8 h after the start with HPLC. RESULTS: In 11/15 patients, seizures were abolished with the addition of midazolam. In the remaining patients, seizure frequency was reduced in one and unchanged in three. Amplitude-integrated EEG background pattern at the start of midazolam was CNV in two, DNV in six, BS in five and CLV in two. Moderate, temporary suppression of the aEEG background pattern lasting less than 2 h was seen in four neonates. Amplitude-integrated EEG at midazolam sampling was CNV in two, DNV in seven, CLV in two and FT in four. Serum levels of midazolam ranged from 0.10 to 1.76 mg/l, OH-midazolam from 0.05 to 0.28 mg/l and glu-midazolam from 0.85 to 4.36 mg/l. CONCLUSIONS: A brief and moderate suppression of the aEEG background pattern immediately after midazolam was seen in four neonates for less than 2 h. Suppression at a later time point, i.e. after more than 8 h of midazolam infusion, was demonstrated almost exclusively in neonates with a poor background pattern, and therefore these patterns appear to be determined mainly by the severity of hypoxic-ischaemic encephalopathy.
Anticonvulsants↗
Tolerance to the discriminative stimulus effects of midazolam: evidence for environmental modification and dose fading.
The ability of behavioral variables to modify the development of tolerance to the discriminative stimulus effects of midazolam was evaluated. Rats were trained to discriminate 0.32mg/kg s.c. or 1.0mg/kg i.p. midazolam from no-drug, under a two-lever procedure, in daily experimental sessions consisting of multiple discrete 20-min trials: 15-min time-out, followed by 5-min under a fixed-ratio 15 schedule of food pellet delivery. Generalization testing was accomplished by administering progressively increasing doses of midazolam before each time-out period. During the chronic phases, twice daily injections of 10mg/kg midazolam or saline were given while discrimination training was either suspended or continued; generalization gradients for midazolam were determined weekly for 4 weeks. Chronic saline given when training was continued or suspended produced slight fluctuations in the midazolam minimal discriminable dose (MDD) (the first dose of midazolam in an individual generalization gradient to produce >/=90% drug-lever responding). Tolerance developed to the discriminative stimulus effects of midazolam when chronic midazolam was given while training was suspended: at Week 4, chronic midazolam produced 3-to 57-fold rightward shifts in the midazolam generalization gradient. In contrast, continued training during chronic midazolam produced no tolerance to the discriminative stimulus effects of midazolam: at Week 4 of chronic midazolam the MDD of midazolam was not different from pre-chronic and not different from either saline condition. The effects of chronic midazolam on stimulus effects and response rates were differentiated: despite tolerance to the stimulus effects of midazolam, there were no consistent changes in response rates during chronic midazolam administration.
Journal Article↗
Comparison of isoflurane and midazolam as hypnotic supplementation to moderately high-dose fentanyl during coronary artery bypass grafting: effects on systemic hemodynamics and early postoperative recovery profile.
OBJECTIVE: The aim of this study was to compare isoflurane and midazolam as hypnotic adjuncts to moderately high-dose fentanyl during coronary artery bypass grafting (CABG) with regard to perioperative hemodynamics and early postoperative recovery profile. DESIGN: Prospective open randomized clinical trial. SETTING: Single university-affiliated medical center. PARTICIPANTS: Thirty patients scheduled for elective primary CABG were randomly divided into two groups receiving either isoflurane or midazolam as adjuncts to 50 micrograms/kg of fentanyl. INTERVENTION: Anesthesia was induced with intravenous fentanyl, 10 micrograms/kg, and midazolam, 0.1 mg/kg, and maintained with either isoflurane, 0.6% or midazolam, 0.1 mg/kg/hour, in intravenous infusion. Before the sternotomy, all patients received 30 micrograms/kg of fentanyl. Midazolam and isoflurane were stopped at the start of cardiopulmonary bypass (CPB). At rewarming, all patients received fentanyl, 5 to 10 micrograms/kg, and either isoflurane, 0.6%, or midazolam, at a reduced rate of 0.05 mg/kg/h. Changes in systolic blood pressure of more than 20% from baseline were first treated with vasoactive drugs. Hypertension was corrected with ketanserin, 10 to 20 mg; hypotension with ephedrine, 5 mg. For a mean blood pressure of less than 50 mmHg during CPB phenylephrine, 0.25 to 0.5 mg, was administered. When hypotension persisted despite a vasopressor, the administration of midazolam or isoflurane was stopped. Postoperatively, the patients were mechanically ventilated overnight and sedated with intermittent doses of fentanyl, 0.15 mg, and midazolam, 5 mg. MEASUREMENTS AND MAIN RESULTS: Routine five-lead electrocardiogram (ECG) and invasive hemodynamic monitoring using a pulmonary artery catheter were performed. The mean dose of fentanyl was 3.9 mg in the midazolam group versus 3.6 mg in the isoflurane group. There were no significant perioperative differences between groups in cardiac output, filling, or pulmonary artery pressures. Systolic blood pressure from the initial incision to CPB was lower in the isoflurane group compared with the midazolam group. During this interval, ketanserin was required in nine patients from the midazolam group at a mean dose of 26 mg, compared with only one patient in the isoflurane group. During and after CPB, there was no difference in ketanserin and in vasopressive/inotropic agent requirements. Temporary cessation of midazolam was required in four patients, for a mean of 34 minutes; whereas isoflurane was stopped in 10 patients for 36 minutes, mostly in the post-CPB period. Time to awakening and to extubation in the midazolam group (217 minutes and 19.5 hours) and the isoflurane group (193 minutes and 18.2 hours) were comparable. Between intensive care unit (ICU) admission and extubation, the patients in the midazolam group received 0.89 mg of fentanyl and 36.5 mg of midazolam compared with 0.98 mg of fentanyl and 36.2 mg of midazolam in the isoflurane group. There was a tendency for a higher postoperative pulmonary shunt and more severely impaired oxygenation in the isoflurane group. CONCLUSION: Midazolam supplementation to fentanyl required more frequent antihypertensive escape during the pre-CPB period than isoflurane. However, more frequent cessation of isoflurane caused by hypotension was needed in the post-CPB period. No difference in awakening and ICU discharge was found.
Aged↗
Effect of midazolam infusion and flumazenil administration on epinephrine arrhythmogenicity in dogs anesthetized with halothane.
BACKGROUND: Midazolam is being selected increasingly for use in patients with cardiovascular compromise. Although clinical doses of midazolam have minimal effects on cardiac function, the influence of midazolam (and other benzodiazepine sedatives) on cardiac arrhythmogenesis has yet to be elucidated fully. METHODS: In this study, we investigated the effect of midazolam, with and without flumazenil, on the arrhythmogenic serum concentration of epinephrine (ACE) in six halothane-anesthetized dogs. Midazolam was administered as a loading dose (1.5 mg/kg over 5 min) followed by a 4.5-h infusion at two rates (10 and 40 micrograms.kg-1 x min-1) to achieve and maintain predetermined clinical and supraclinical plasma midazolam concentrations. The arrhythmogenic serum concentration of epinephrine determinations were made prior to midazolam infusion, following 2 h of midazolam infusion and following 3.5 h of midazolam infusion and 1 mg flumazenil/kg i.v. Saline control studies were also performed in four of the six dogs. RESULTS: Plasma midazolam concentrations ranged from 363 to 855 ng/ml in the low-dose infusion study, essentially spanning the clinically effective range for humans. In the high-dose infusion study, plasma midazolam concentrations were up to four times greater, ranging from 1168 to 3563 ng/ml. The arrhythmogenic serum concentration of epinephrine values were unchanged following low-dose midazolam infusion and saline. In the high-dose study, ACE increased from baseline values of 68 +/- 13 (SEM) ng/ml to 112 +/- 25 ng/ml (P = .03) following midazolam infusion and decreased to 79 +/- 13 ng/ml with flumazenil administration. Plasma midazolam concentrations, however, were poorly correlated with ACE values normalized for control ACE (ACE ratio). Diastolic arterial pressure was significantly depressed following both low-dose (-14%) and high-dose (-19%) midazolam infusion. This decrease in blood pressure was unaffected by flumazenil administration. Other hemodynamic parameters were unaffected by drug treatment. CONCLUSIONS: This study has demonstrated that midazolam infusion results in either no effect (with clinical plasma midazolam concentrations) or flumazenil-reversible suppression (with supraclinical concentrations) of halothane-epinephrine arrhythmogenesis.
Anesthesia, Inhalation↗
No evidence of a genetic polymorphism in the oxidative metabolism of midazolam.
The benzodiazepine midazolam is rapidly eliminated by oxidative metabolism. In young healthy volunteers elimination half-life (t1/2) is about 2.4 hours. A recent study showed a prolonged t1/2 from 8 to 22 hours in 6.5% of surgical patients, and a genetic polymorphism of midazolam's metabolism has been suggested. Therefore, we measured in 168 surgical patients the elimination of midazolam and its major hydroxylated metabolite (alpha-OH-midazolam) in blood and urine. Co-medication, disease status, smoking habits and alcohol intake were recorded; normal liver and kidney functions were assessed by routine laboratory tests. Midazolam was administered intravenously (0.1 to 0.2 mg/kg) for the induction of anaesthesia. Blood was drawn 1.5, 3, 4.5 and 6 hours after application and urine was collected for 6 hours. Plasma protein binding of midazolam was determined by equilibrium dialysis. Midazolam and alpha-OH-midazolam were measured in plasma by specific gas-liquid chromatography and in urine by high performance liquid chromatography. Data for the dose-corrected area under plasma-level curve of midazolam (AUC-midazolam/dose: 1.23 +/- 961 x 10(5) h/ml; mean +/- SD) and for the metabolic plasma ratio (AUC of alpha-OH-midazolam/AUC-midazolam: 0.52 +/- 0.28) demonstrated a log-normal distribution. Likewise, the percentage of the unbound fraction of midazolam in plasma (5.0 +/- 2.4%), urinary excretion of alpha-OH-midazolam (55.9 +/- 22.7% of dose) and the values for t1/2 (2.9 +/- 1.1 hours) did indicate a unimodal distribution. Age, comedication and smoking habits did not affect the disposition of midazolam. However, patients with regular intake of alcohol had a higher (p less than 0.05) metabolic ratio. Only in 3 patients could a prolonged t1/2 of midazolam from 7.5 to 10.2 hours be detected, but plasma levels and urinary excretion of alpha-OH-midazolam in those individuals were found to be normal. Therefore it is very unlikely that the oxidative metabolism of midazolam exhibits a genetic polymorphism.
Age Factors↗
Effect of saquinavir on the pharmacokinetics and pharmacodynamics of oral and intravenous midazolam.
OBJECTIVE: To assess the effect of human immunodeficiency virus protease inhibitor saquinavir on the pharmacokinetics and pharmacodynamics of oral and intravenous midazolam. METHODS: In a double-blind, randomized, two-phase crossover study, 12 healthy volunteers (six men and six women; age range, 21 to 32 years) received oral doses of either 1200 mg saquinavir (Fortovase soft-gel capsule formulation) or placebo three times a day for 5 days. On day 3, six subjects were given 7.5 mg oral midazolam and the other six subjects received 0.05 mg/kg intravenous midazolam. On day 5, the subjects who had received oral midazolam on day 3 received intravenously midazolam and vice versa. Plasma concentrations of midazolam, alpha-hydroxymidazolam, and saquinavir were determined for 18 hours after midazolam administration, and midazolam effects were measured up to 7 hours by six psychomotor tests. RESULTS: Saquinavir increased the bioavailability of oral midazolam from 41% to 90% (P < .005), the peak midazolam plasma concentration more than twofold, and the area under plasma concentration-time curve more than fivefold (P < .001). During saquinavir treatment, five of the six psychomotor tests revealed impaired skills and increased sedative effects after midazolam ingestion (P < .05). Saquinavir decreased the clearance of intravenous midazolam by 56% (P < .001) and increased its elimination half-life from 4.1 to 9.5 hours (P < .01). After intravenous midazolam, only the subjective feeling of drug effect was increased significantly (P < .05) by saquinavir. CONCLUSION: The dose of oral midazolam should be greatly reduced or avoided with saquinavir, but bolus doses of intravenous midazolam can probably be used quite safely. During a prolonged midazolam infusion, an initial dose reduction of 50% followed by careful titration is recommended to counteract the reduced clearance caused by saquinavir.
Administration, Oral↗
Does midazolam alter the clinical effects of intravenous ketamine sedation in children? A double-blind, randomized, controlled, emergency department trial.
STUDY OBJECTIVE: This study was conducted to investigate the frequency and severity of adverse effects, specifically emergence phenomena, experienced by patients receiving intravenous ketamine with or without midazolam for sedation in a pediatric emergency department. METHODS: Patients aged 4.5 months to 16 years receiving ketamine sedation were prospectively enrolled in a double-blind, randomized, controlled study at a university-affiliated children's hospital-pediatric ED. All patients received ketamine (1 mg/kg) and glycopyrrolate (5 microgram/kg) intravenously. Patients were randomly assigned to receive midazolam (0.1 mg/kg) intravenously or no midazolam. Total time of sedation, sedation efficacy, and adverse effects were recorded. Adverse effects were compared between patients receiving ketamine versus those who received ketamine and midazolam. Additional comparisons were made based on age and number of ketamine doses administered. RESULTS: Two hundred sixty-six patients were studied; 129 received ketamine and 137 patients received ketamine and midazolam. Time of sedation and efficacy of sedation were equivalent between groups. Overall, adverse effects with ketamine sedation included respiratory events (12 [4.5%]), vomiting (50 [18.7%]), emergence phenomena in the pediatric ED (71 [26.7%]), and emergence phenomena at home (60 [22.4%]). Significant emergence phenomena in the pediatric ED (ie, nightmares, hallucinations, and severe agitation) occurred in 7.1% of the ketamine group and in 6.2% of the ketamine-midazolam group, a rate difference of 0.8 (95% confidence interval [CI] -5.3 to 7.0). The addition of midazolam led to an increased incidence of oxygen desaturation events (ketamine 1.6% versus ketamine-midazolam 7.3%; rate difference -5.7, 95% CI -10.6 to -0.9) but a decreased incidence of vomiting (ketamine 19.4%, ketamine-midazolam 9.6%, rate difference 9.8, 95% CI 1.4 to 18.2). The incidence of emergence phenomena and significant emergence phenomena was not affected by the addition of midazolam. However, the addition of midazolam was associated with more agitation in the pediatric ED in children 10 years or older (ketamine 5.7% versus ketamine-midazolam 35.7%; rate difference -30.0, 95% CI -10.7 to -49.3). Age breakdown further showed 6.3% (95% CI 0.9 to 11.6) more episodes of oxygen desaturation in the ketamine-midazolam group in children younger than 10 years, and 12.1% (95% CI 1.5 to 22.6) more vomiting episodes in the ketamine group in children younger than 10 years. CONCLUSION: Ketamine and combined ketamine and midazolam provided equally effective sedation. The addition of midazolam did not alter the incidence of emergence phenomena. Vomiting occurred more frequently in the ketamine only group, whereas oxygen desaturation occurred more frequently in the ketamine-midazolam group. These findings were more pronounced in patients younger than 10 years. Parental and physician satisfaction remained high for all patients receiving intravenous ketamine sedation.
Adolescent↗
Oral administration of a low dose of midazolam (75 microg) as an in vivo probe for CYP3A activity.
OBJECTIVE: We investigated whether the oral administration of a low dose (75 micro g) of midazolam, a CYP3A probe, can be used to measure the in vivo CYP3A activity. METHODS: Plasma concentrations of midazolam, 1'OH-midazolam and 4'OH-midazolam were measured after the oral administration of 7.5 mg and 75 micro g midazolam in 13 healthy subjects without medication, in four subjects pretreated for 2 days with ketoconazole (200 mg b.i.d.), a CYP3A inhibitor, and in four subjects pretreated for 4 days with rifampicin (450 mg q.d.), a CYP3A inducer. RESULTS: After oral administration of 75 micro g midazolam, the 30-min total (unconjugated + conjugated) 1'OH-midazolam/midazolam ratios measured in the groups without co-medication, with ketoconazole and with rifampicin were (mean+/-SD): 6.23+/-2.61, 0.79+/-0.39 and 56.1+/-12.4, respectively. No side effects were reported by the subjects taking this low dose of midazolam. Good correlations were observed between the 30-min total 1'OH-midazolam/midazolam ratio and midazolam clearance in the group without co-medication (r(2)=0.64, P<0.001) and in the three groups taken together (r(2)=0.91, P<0.0001). Good correlations were also observed between midazolam plasma levels and midazolam clearance, measured between 1.5 h and 4 h. CONCLUSION: A low oral dose of midazolam can be used to phenotype CYP3A, either by the determination of total 1'OH-midazolam/midazolam ratios at 30 min or by the determination of midazolam plasma levels between 1.5 h and 4 h after its administration.
Adult↗
Synergistic sedation with propofol and midazolam in intensive care patients after coronary artery bypass grafting.
OBJECTIVES: To evaluate and compare the clinical efficacy, impact on hemodynamics, safety profiles, and cost of combined administration of propofol and midazolam (synergistic sedation) vs. midazolam and propofol administered as sole agents, for sedation of mechanically ventilated patients after coronary artery bypass grafting. DESIGN: Prospective, controlled, randomized, double-blind clinical trial. SETTING: Intensive care unit of SCIAS-Hospital de Barcelona. PATIENTS: Seventy-five mechanically ventilated patients who underwent coronary artery bypass graft surgery under low-dose opioid anesthesia. INTERVENTIONS: According to the double-blind method, patients were randomly assigned to receive propofol (n = 25), midazolam (n = 25), or propofol combined with midazolam (n = 25). Infusion rates were adjusted to stay between 8 and 11 points on Glasgow Coma Score modified by Cook and Palma. MEASUREMENTS AND MAIN RESULTS: Mean +/- SD duration of sedation was 14.4 +/- 1.5 hrs, 14.1 +/- 1.1 hrs, and 14.7 +/- 1.9 hrs for the propofol, midazolam, and synergistic groups, respectively. The induction dose was 0.55 +/- 0.05 mg/kg for propofol as sole agent, 0.05 +/- 0.01 mg/kg for midazolam as sole agent, and 0.22 +/- 0.03 mg/kg for propofol administered in combination with 0.02 +/- 0.00 mg/kg of midazolam (p = .001). The maintenance dose was 1.20 +/- 0.03 mg/kg/hr for propofol as sole agent, 0.08 +/- 0.01 mg/kg/hr for midazolam as sole agent, and 0.50 +/- 0.09 mg/kg/hr for propofol administered in combination with 0.03 +/- 0.01 mg/kg/hr of midazolam (p < .001). All sedative regimens achieved similar efficacy in percentage of hours of adequate sedation (93% for propofol, 88% for midazolam, and 90% for the synergistic group, respectively). After induction, both propofol and midazolam groups had significant decreases in systolic blood pressure, diastolic blood pressure, left atrial pressure, and heart rate. Patients in the synergistic group had significant bradycardia throughout the study, without impairment in other hemodynamic parameters. Patients sedated with propofol or synergistic regimen awoke sooner and could be extubated before those patients sedated with midazolam (0.9 +/- 0.3 hrs and 1.2 +/- 0.6 hrs vs. 2.3 +/- 0.8 hrs, respectively, p = .01). Synergistic sedation produced cost savings of 28% with respect to midazolam and 68% with respect to propofol. CONCLUSIONS: In the study conditions, the new synergistic treatment with propofol and midazolam administered together is an effective and safe alternative for sedation, with some advantages over the conventional regimen with propofol or midazolam administered as sole agents, such as absence of hemodynamic impairment, >68% reduction in maintenance dose, and lower pharmaceutical cost.
Adult↗
Oral single doses of erythromycin and roxithromycin may increase the effects of midazolam on human performance.
Macrolide antibiotics are known to inhibit the metabolism of triazolam and midazolam in vitro and in vivo. To find out if significant interactions take place after single oral doses of these agents to man, 0.25 mg triazolam and 5, 10 and 15 mg of midazolam in capsule from were given with and without 750 mg erythromycin or 300 mg roxithromycin to parallel groups of healthy subjects in four placebo-controlled double-blind studies. Objective tests and subjective assessments were made before the intake of hypnotics and 30 and 90 min after it. In Study I, triazolam impaired letter cancellation, the combination triazolam+erythromycin impaired digit symbol substitution and letter cancellation, and triazolam+roxithromycin impaired digit symbol substitution, all at 90 min. In Study II, midazolam 5 mg and midazolam 10 mg proved quite inert but the combination midazolam 5 mg+erythromycin impaired digit symbol substitution. In Study III, both midazolam 10 mg and midazolam 15 mg impaired digit substitution and letter cancellation, the effects of 15 mg being more prominent. The strongest drug effects were found with midazolam 10 mg+erythromycin which differed from placebo and midazolam (10 mg and 15 mg) in several objective and subjective test variables. In Study IV, the combination midazolam 10 mg+roxithromycin impaired several objective and subjective variables but it was not stronger than midazolam 15 mg. These results were supported by the direct measurements of plasma midazolam in three subjects: erythromycin increased plasma midazolam more than roxithromycin and enhanced midazolam effects following the intake of midazolam 10 mg.(ABSTRACT TRUNCATED AT 250 WORDS)
Administration, Oral↗
Midazolam is a phenobarbital-like cytochrome p450 inducer in rats.
Midazolam is almost exclusively metabolized by cytochrome P450 3A (CYP3A) isoenzymes. Therefore, midazolam is used as a probe to determine CYP3A levels in humans and rats. A prerequisite for longitudinal determination of CYP3A expression levels using midazolam as a probe is that midazolam itself has no effect on the expression of CYP3A. In the present study, we analyzed the mRNA levels and enzyme activities of the major CYP isoforms in the rat liver after intraperitoneal injection of midazolam (50 mg/kg) for 3 consecutive days. CYP3A1 mRNA levels were increased 4-fold in midazolam-treated animals compared with controls, whereas the mRNA levels of CYP3A2, CYP3A9, and CYP3A18 were not altered. The increase in CYP3A1 mRNA was accompanied by a 25% increase in microsomal testosterone 6beta-hydroxylation activity. More strikingly, CYP2B1/2 mRNA levels were increased 22-fold upon midazolam treatment, leading to an 11- to 95-fold enhancement of CYP2B enzyme activity. CYP2C6 mRNA levels were 4 times higher in midazolam-treated animals. Formation of 2alpha-hydroxy-testosterone, mainly catalyzed by CYP2C11, was 2.6-fold lower in liver microsomes from midazolam-treated animals. Midazolam induced CYP2E enzyme activity 2.5-fold at the post-transcriptional level. The induction of CYP2B1/2 mRNA levels by midazolam was dose-dependent (4.5-fold increase at 10 mg/kg). Induction of CYP3A1 and CYP2B expression was also observed in isolated rat hepatocytes cultured with 100 microM midazolam. We conclude that midazolam is a phenobarbital-like CYP inducer in rats. Induction of CYP3A1 by midazolam may have implications for the longitudinal use of midazolam as a probe for analysis of CYP3A expression levels in rats.
Animals↗
Midazolam exhibits characteristics of a highly permeable P-glycoprotein substrate.
PURPOSE: The purpose of this study was to investigate whether midazolam exhibits characteristics of a highly permeable P-glycoprotein (P-gp) substrate and to evaluate the potential influence of P-gp inhibition on 1-OH midazolam formation during midazolam transport. METHODS: P-gp interaction was investigated by P-gp ATPase assay, efflux inhibition studies, and transport studies of midazolam across MDR1-MDCK and 1-alpha,25-dihydroxy vitamin D3-induced Caco-2 monolayers with and without the P-gp inhibitor GF120918. RESULTS: Midazolam was highly permeable and transport appeared essentially unpolarized. In MDR1-MDCK, the basolateral-to-apical (B-to-A) permeability was slightly higher (16%) than apical-to-basolateral (A-to-B) permeability (p = 0.04); GF120918 increased A-to-B permeability by 27% (p = 0.01), and increased cellular midazolam accumulation during A-to-B transport by 45% (p = 0.01). Midazolam (200 microM) decreased rhodamine123 and vinblastine B/A ratios 3-fold (p < 0.006), while increasing their cellular accumulation (p < 0.003). P-gp ATPase activation by midazolam was dose-dependent and saturable [Km = 11.5(+/- 4.0) microM; Vmax = 41.1(+/- 7.4) nmol/mg/min]. P-gp inhibition increased 1-OH midazolam formation in A-to-B studies 1.3-fold when midazolam donor > or = 10 microM (p < 0.03). In B-to-A studies, P-gp inhibition did not significantly increase metabolite formation (p = 0.06). Midazolam's extraction ratio was not influenced by P-gp (p = 0.2). CONCLUSION: The results indicate that midazolam exhibited characteristics of a highly permeable P-gp substrate. 1-OH midazolam formation during A-to-B midazolam transport increased slightly when P-gp was inhibited.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Pharmacokinetics and metabolism of intravenous midazolam in preterm infants.
BACKGROUND: Midazolam, a benzodiazepine, is finding expanded use in neonatal intensive care units. We studied the pharmacokinetics and metabolism of midazolam after a single intravenous dose in preterm infants. METHODS: The pharmacokinetics of midazolam and its hydroxylated metabolite (1-OH-midazolam) after a single 0.1 mg/kg intravenous dose of midazolam were determined in 24 preterm infants (gestational age, 26 to 34 weeks; postnatal age, 3 to 11 days). Blood samples were obtained before drug administration and at 0.5, 1, 2, 4, 6, 12, and 24 hours after the start of the infusion. Midazolam and 1-OH-midazolam concentrations were determined by use of gas chromatography-mass spectrometry. RESULTS: Total body clearance, apparent volume of distribution, and plasma half-life of midazolam were (median [range]): 1.8 (0.7-6.7) ml/kg per min, 1.1 (0.4-4.2) L/kg, and 6.3 (2.6-17.7) h, respectively. In 19 of 24 preterm infants, 1-OH-midazolam concentrations could be detected: 1-OH-midazolam (1-OH-M) maximal concentration of drug in plasma (C(max)), time to reach C(max) (T(max)), and 1-OH-M/M area under the concentration-time curve from time zero to the last sampling time point (AUC(0-t)) ratio were [median (range)]: 8.2 (<0.5-68.2) ng/ml, 6 (1-12) h, and 0.09 (<0.001-1), respectively. Midazolam plasma clearance was increased in those infants who had indomethacin (INN, indometacin) exposure. DISCUSSION: Consequent to immature hepatic cytochrome P450 3A4 (CYP3A4) activity, midazolam clearance and 1-OH-midazolam concentrations are reduced markedly in preterm infants as compared to concentrations in previous reports from studies in older children and adults. Indomethacin exposure and its apparent impact on midazolam clearance support alteration of drug disposition produced by a patent ductus arteriosus or by the direct effects of indomethacin on hemodynamic or renal function.
Anti-Anxiety Agents↗
The effect of intravenous administration of variable-dose midazolam after fixed-dose ketamine in healthy awake cats.
The effects of intravenous administration of variable-dose midazolam and ketamine (3 mg/kg) were studied in twelve healthy unmedicated cats from time of administration until full recovery. A range of midazolam doses (0.0, 0.05, 0.5, 1.0, 2.0 and 5.0 mg/kg) was chosen, so that beneficial and/or detrimental effects could be documented and the therapeutic window for further study determined. One minute after administration of ketamine, all cats had assumed a lateral position, mostly with head up. Muscle tone was increased (100%), apneustic breathing pattern evident in 92% of cats, chewing without stimulation of the oropharyngeal area was observed in most cats (97%), but most cats did not salivate (87%). At 2.5 min after completion of ketamine injection and 1 min after administration of saline, a similar picture was observed, except that salivation was evident. All cats chewed or swallowed in response to a finger or laryngoscope placed in the oropharyngeal area and, while most cats were not aware of a noxious stimulus to the tail, some cats were aware of a noxious stimulus to the paw. Recovery from ketamine alone was rapid and smooth with cats rolling into sternal recumbency and then cautiously walking with ataxia. Recovery to walking without incoordination was also rapid (< 2 h) and no abnormal behavioural patterns were observed during recovery. Administration of midazolam after ketamine, had beneficial effects and the therapeutic window for midazolam was found to lie between 0.05 mg/kg and 0.5 mg/kg. Administration of any dose of midazolam after ketamine caused a greater proportion of cats to assume a laterally recumbent position with head down compared with ketamine alone, however, the time period of recumbency was only significantly longer with a midazolam dose of 2.0 mg/kg or above. Doses of midazolam of 0.5 mg/kg or above decreased muscle rigidity but did not affect salivation or respiratory pattern observed in cats which received ketamine alone. A significantly greater proportion of cats which received ketamine and midazolam 0.5 mg/kg or above did not swallow in response to a finger or a laryngoscope placed in the mouth compared with that which received ketamine alone. The length of time in which cats did not swallow was only significantly longer at midazolam doses of 1.0 mg/kg and above. At midazolam doses of 0.5 mg/kg or above, the proportion of cats without a nociceptive response to a tail or paw clamp was significantly greater than cats which received ketamine alone. The time period without nociceptive response, however, was not influenced by midazolam administration. The time taken for cats which received ketamine and midazolam 0.05 mg/kg or 0.5 mg/kg to assume sternal position, walk with ataxia, walk without ataxia, behave normally when approached or restrained and recover normal arousal state was not significantly different from cats which received ketamine alone. Ketamine and midazolam 5.0 mg/kg significantly prolonged all recovery times compared with ketamine alone. Unfortunately, a greater proportion of cats which received ketamine and midazolam 0.5 or 5.0 mg/kg exhibited detrimental behavioural effects. These were more likely to be adverse and included restlessness, vocalization and difficulty approaching and restraining cats. In this study, an effect of sex of the cats was found, with male cats taking a significantly longer to recover to sternal recumbency and walk with ataxia, while female cats took longer to recover to a normal arousal state.
Anesthetics, Dissociative↗