Absolute bioavailability of midazolam after subcutaneous administration to healthy volunteers

Safety, Pharmacokinetics, and Pharmacodynamics of Midazolam Gel After Rectal Administration in Healthy Chinese Subjects

BACKGROUND AND OBJECTIVES

Midazolam rectal gel is a novel rectal formulation that may be a promising and potential alternative to oral administration for pediatric sedation. The objective of this study was to evaluate the safety, pharmacokinetics, pharmacodynamics, and absolute bioavailability of midazolam rectal gel in healthy Chinese subjects.

METHODS

An open-label, single-dose, randomized, two-period, two-treatment, crossover clinical study was conducted in 22 healthy subjects (16 males and six females), each receiving 2.5 mg intravenous midazolam in one period and 5 mg midazolam rectal gel in another period (the dosages here were calculated as active midazolam). Safety, pharmacokinetic, and pharmacodynamic assessments were conducted throughout the study.

RESULTS

All of the subjects completed both treatment periods. The formulation of rectal gel was well tolerated, with no serious adverse events occurring. After a single rectal dose of 5 mg midazolam rectal gel, it was absorbed rapidly with a median value of time to peak concentration (T_max) of 1.00 h, and mean values of the peak concentration (C_max) and area under the concentration-time curve (AUC_0-t) of 37.2 ng/mL and 137 h·ng/mL, respectively. The absolute bioavailability of rectal gel was 59.7%. The rectal gel exhibited a relatively delayed onset but a more stable sedative effect and a longer duration when compared with intravenous midazolam.

CONCLUSION

Midazolam rectal gel may be a feasible alternative with a high level of acceptance in pediatric sedation and enhanced bioavailability compared to an oral formulation. The modeling results may help to disclose out the exposure-response relationship of midazolam rectal gel and support the design of an escalating-doses study and pediatric extrapolation study.

CLINICAL TRIAL REGISTRATION

The study was registered at http://www.chinadrugtrials.org.cn (No. CTR20192350).

Efficacy of Proportional Sedation and Deep Sedation Defined by Sedation Protocols: A Multicenter, Prospective, Observational Comparative Study

PURPOSE

To investigate the efficacy of two types of palliative sedation: proportional and deep sedation, defined by sedation protocols.

METHODS

From a multicenter prospective observational study, we analyzed the data of those patients who received the continuous infusion of midazolam according to the sedation protocol. The primary endpoint was goal achievement at 4 hours: in proportional sedation, symptom relief (Integrated Palliative care Outcome Scale: IPOS ≤ 1) and absence of agitation (modified Richmond Agitation-Sedation Scale: RASS ≤ 0); in deep sedation, the achievement of deep sedation (RASS ≤ -4). Secondary endpoints included deep sedation as a result of proportional sedation, communication capacity (Communication Capacity Scale item 4 ≤ 2), IPOS and RASS scores, and adverse events.

RESULTS

A total of 81 patients from 14 palliative care units were analyzed: proportional sedation (n = 64) and deep sedation (n = 17). At 4 hours, the goal was achieved in 77% (n = 49; 95% confidence interval: 66-87) with proportional sedation; and 88% (n = 15; 71-100) with deep sedation. Deep sedation was necessary in 45% of those who received proportional sedation. Communication capacity was maintained in 34% with proportional sedation and 10% with deep sedation. IPOS decreased from 3.5 to 0.9 with proportional sedation, and 3.5 to 0.4 with deep sedation; RASS decreased from +0.3 to -2.6, and +0.4 to -4.2, respectively. Fatal events related to the treatment occurred in 2% (n = 1) with proportional and none with deep sedation.

CONCLUSION

Proportional sedation achieved satisfactory symptom relief while maintaining some patients' consciousness, and deep sedation achieved good symptom relief while the majority of patients lost consciousness.

First dose in neonates: pharmacokinetic bridging study from juvenile mice to neonates for drugs metabolized by CYP3A

First dose prediction is challenging in neonates. Our objective in this proof-of-concept study was to perform a pharmacokinetic (PK) bridging study from juvenile mice to neonates for drugs metabolized by CYP3A. We selected midazolam and clindamycin as model drugs. We developed juvenile mice population PK models using NONMEM. The PK parameters of these two drugs in juvenile mice were used to bridge PK parameters in neonates using different correction methods. The bridging results were evaluated by the fold-error of 0.5- to 1.5-fold. Simple allometry with and without a correction factor for maximum lifespan potential could be used for a bridging of clearance (CL) and volume of distribution (V_d), respectively, from juvenile mice to neonates. Simulation results demonstrated that for midazolam, 100% of clinical studies for which both the predictive CL and V_d were within 0.5- to 1.5-fold of the observed. For clindamycin, 75% and 100% of clinical studies for which the predictive CL and V_d were within 0.5- to 1.5-fold of the observed. A PK bridging of drugs metabolized by CYP3A is feasible from juvenile mice to neonates. It could be a complement to the ADE and PBPK models to support the first dose in neonates.

Midazolam: an essential palliative care drug

Midazolam is a commonly used benzodiazepine in palliative care and is considered one of the four essential drugs needed for the promotion of quality care in dying patients. Acting on the benzodiazepine receptor, it promotes the action of gamma-aminobutyric acid. Gamma-aminobutyric acid action promotes sedative, anxiolytic, and anticonvulsant properties. Midazolam has a faster onset and shorter duration of action than other benzodiazepines such as diazepam and lorazepam lending itself to greater flexibility in dosing than other benzodiazepines. The kidneys excrete midazolam and its active metabolite. Metabolism occurs in the liver by the P450 system. This article examines the pharmacology, pharmacodynamics, and clinical uses of midazolam in palliative care.

Midazolam: Safety of use in palliative care: A systematic critical review

PURPOSE

The undesired effects of midazolam can be life-threatening. This paper delineates the findings related to the pharmacokinetics, adverse effects and drug-drug interactions as well as associated therapeutic implications for safe midazolam use.

METHODS

A systematic review of literature was conducted.

RESULTS

The pharmacokinetics of midazolam depends on hepatic and renal functions, fat tissue mass, route and duration of administration, as well as potential drug-drug interactions. Palliative care patients constitute a high-risk group prone to side effects of drugs, due to polytherapy and multi-organ failure.

CONCLUSION

Midazolam is one of three most frequently administered drugs in palliative care. The indications for its use include anxiety, dyspnea, seizures, vomiting refractory to treatment, agitation, myoclonus, status epilepticus, restlessness, delirium, pruritus, hiccups, insomnia, analgosedation, palliative sedation and preventing or counteracting undesired effects of ketamine.

Intravenous versus Subcutaneous Midazolam Using Jet-injector in Pediatric Sedation; a Randomized Clinical Trial

INTRODUCTION

The quality of interventions in children is largely dependent on their control. Hence, this study compared the sedative effects of subcutaneous (SC) and intravenous (IV) Midazolam in pediatric sedation induction.

METHODS

This randomized clinical trial was conducted on children aged 1-6 years presenting to emergency departments of Shahid Sadoughi and Shahid Rahnemoon Hospitals, Yazd, Iran. Participants were randomly assigned to IV or SC midazolam using a jet injector and success rate, degree of sedation, and satisfaction of parents and physician were compared between groups.

RESULTS

60 cases with the mean age of 3.15±1.43 (1-6) years were randomly assigned to the SC (30 cases) or IV (30 cases) groups (56.7% female). SC and IV groups were similar regarding the mean age (p = 0.165) and sex (p = 0.121). Depth of sedation (p=0.900), control of child (p=0.711), in-charge physician's satisfaction (p=0.467), successful sedation and need for rescue dose (p=0.519) were not different between groups. IV midazolam group had a significantly shorter recovery time (about 10 minutes; p=0.040) and SC midazolam group had a significantly higher level of parent satisfaction (p=0.001).

CONCLUSION

The findings indicate no significant difference in depth of sedation, control of child, in-charge physician's satisfaction, successful sedation (reaching stage 1 of sedation or higher), and need for rescue dose of SC and IV midazolam. Parents' satisfaction was significantly greater with SC administration and IV injection had shorter recovery time.

Efficacy of two types of palliative sedation therapy defined using intervention protocols: proportional vs. deep sedation

PURPOSE

This study investigated the effect of two types of palliative sedation defined using intervention protocols: proportional and deep sedation.

METHODS

We retrospectively analyzed prospectively recorded data of consecutive cancer patients who received the continuous infusion of midazolam in a palliative care unit. Attending physicians chose the sedation protocol based on each patient's wish, symptom severity, prognosis, and refractoriness of suffering. The primary endpoint was a treatment goal achievement at 4 h: in proportional sedation, the achievement of symptom relief (Support Team Assessment Schedule (STAS) ≤ 1) and absence of agitation (modified Richmond Agitation-Sedation Scale (RASS) ≤ 0) and in deep sedation, the achievement of deep sedation (RASS ≤ - 4). Secondary endpoints included mean scores of STAS and RASS, deep sedation as a result, and adverse events.

RESULTS

Among 398 patients who died during the period, 32 received proportional and 18 received deep sedation. The treatment goal achievement rate was 68.8% (22/32, 95% confidence interval 52.7-84.9) in the proportional sedation group vs. 83.3% (15/18, 66.1-100) in the deep sedation group. STAS decreased from 3.8 to 0.8 with proportional sedation at 4 h vs. 3.7 to 0.3 with deep sedation; RASS decreased from + 1.2 to - 1.7 vs. + 1.4 to - 3.7, respectively. Deep sedation was needed as a result in 31.3% (10/32) of the proportional sedation group. No fatal events that were considered as probably or definitely related to the intervention occurred.

CONCLUSION

The two types of intervention protocol well reflected the treatment intention and expected outcomes. Further, large-scale cohort studies are promising.

A combination of alfaxalone, medetomidine and midazolam for the chemical immobilization of Rhesus macaque (Macaca mulatta): Preliminary results

BACKGROUND

Chemical immobilization of non-human primates can be required to perform scientific or veterinary procedure with different invasiveness degrees. This preliminary study was undertaken to assess the clinical effects of a combination of alfaxalone, medetomidine and midazolam (AMM).

METHODS

Seven rhesus macaques were chemically immobilized, for invasive veterinary procedures, with alfaxan 2 mg kg^-1 , medetomidine 20 μg kg^-1 and midazolam 0.3 mg kg^-1 injected subcutaneously.

RESULTS

The alfaxalone combination induced surgical anaesthesia, with a complete absence of response to noxious stimuli, for at least 20 minutes. The total duration of anaesthesia was 56 ± 7 minutes, and the administration of atipamezole, to partially reverse the combination effects, did not appear to alter the depth of anaesthesia.

CONCLUSION

In conclusion, the AMM combination produced rapid onset general anaesthesia, following subcutaneous administration of a relatively low volume (0.28 mL/kg) of injectate.

Hypoalbuminaemia and decreased midazolam clearance in terminally ill adult patients, an inflammatory effect?

AIMS

Midazolam is the drug of choice for palliative sedation and is titrated to achieve the desired level of sedation. Because of large inter-individual variability (IIV), however, the time it takes to achieve adequate sedation varies widely. It would therefore greatly improve clinical care if an individualized dose could be determined beforehand. To find clinically relevant parameters for dose individualization, we performed a pharmacokinetic study on midazolam, 1OH-midazolam (1-OH-M) and 1OH-midazolam-glucuronide (1-OH-MG) in terminally ill patients.

METHODS

Using nonlinear mixed effects modelling (NONMEM 7.2), a population pharmacokinetic analysis was conducted with 192 samples from 45 terminally ill patients who received midazolam either orally or subcutaneously. The covariates analysed were patient characteristics, co-medication and blood chemistry levels.

RESULTS

The data were accurately described by a one compartment model for midazolam, 1-OH-M and 1-OH-MG. The population mean estimates for midazolam, 1-OH-M and 1-OH-MG clearance were 8.4 l h^-1 (RSE 9%, IIV 49%), 45.4 l h^-1 (RSE 12%, IIV 60.5%) and 5.1 l h^-1 (RSE 11%, IIV 49.9%), respectively. 1-OH-MG clearance was correlated with the estimated glomular filtration rate (eGFR) explaining 28.4% of the IIV in 1-OH-MG clearance. In addition, low albumin levels were associated with decreased midazolam clearance, explaining 18.2% of the IIV.

CONCLUSION

Our study indicates albumin levels and eGFR as relevant clinical parameters to optimize midazolam dosing in terminally ill patients. The correlation between low albumin levels and decreased midazolam clearance is probably a result of inflammatory response as high CRP levels were correlated in a similar way.

A Review of Agents for Palliative Sedation/Continuous Deep Sedation: Pharmacology and Practical Applications

Continuous deep sedation at the end of life is a specific form of palliative sedation requiring a care plan that essentially places and maintains the patient in an unresponsive state because their symptoms are refractory to any other interventions. Because this application is uncommon, many providers may lack practical experience in this specialized area and resources they can access are outdated, nonspecific, and/or not comprehensive. The purpose of this review is to provide an evidence- and experience-based reference that specifically addresses those medications and regimens and their practical applications for this very narrow, but vital, aspect of hospice care. Patient goals in a hospital and hospice environments are different, so the manner in which widely used sedatives are dosed and applied can differ greatly as well. Parameters applied in end-of-life care that are based on experience and a thorough understanding of the pharmacology of those medications will differ from those applied in an intensive care unit or other medical environments. By recognizing these different goals and applying well-founded regimens geared specifically for end-of-life sedation, we can address our patients' symptoms in a more timely and efficacious manner.

Pharmacokinetics and pharmacodynamics of a new highly concentrated intranasal midazolam formulation for conscious sedation

AIM

To evaluate the pharmacokinetics, pharmacodynamics, nasal tolerance and effects on sedation of a highly concentrated aqueous intranasal midazolam formulation (Nazolam) and to compare these to intravenous midazolam.

METHODS

In this four-way crossover, double-blind, double-dummy, randomized, placebo-controlled study, 16 subjects received 2.5 mg Nazolam, 5.0 mg Nazolam, 2.5 mg intravenous midazolam or placebo on different occasions. Pharmacokinetics of midazolam and α-hydroxy-midazolam were characterized and related to outcome variables for sedation (saccadic peak velocity, the Bond and Lader visual analogue scale for sedation, the simple reaction time task and the observer's assessment of alertness/sedation). Nasal tolerance was evaluated through subject reporting, and ear, nose and throat examination.

RESULTS

Nazolam bioavailability was 75%. Maximal plasma concentrations of 31 ng ml^-1 (CV, 42.3%) were reached after 11 min (2.5 mg Nazolam), and of 66 ng ml^-1 (coefficient of variability, 31.5%) after 14 min (5.0 mg Nazolam). Nazolam displayed a significant effect on OAA/S scores. Sedation onset (based on SPV change) occurred 1 ± 0.7 min after administration of 2.5 mg intravenous midazolam, 7 ± 4.4 min after 2.5 mg Nazolam, and 4 ± 1.8 min after 5 mg Nazolam. Sedation duration was 118 ± 95.6 min for 2.5 mg intravenous midazolam, 76 ± 80.4 min for 2.5 mg Nazolam, and 145 ± 104.9 min for 5.0 mg Nazolam. Nazolam did not lead to nasal mucosa damage.

CONCLUSIONS

This study demonstrates the nasal tolerance, safety and efficacy of Nazolam. When considering the preparation time needed for obtaining venous access, conscious sedation can be achieved in the same time span as needed for intravenous midazolam. Nazolam may offer important advantages in conscious sedation.

Bispectral Index Monitoring in Terminally Ill Patients: A Validation Study

CONTEXT

If regular therapies cannot relieve symptoms sufficiently in the last days of life, continuous palliative sedation may serve to reduce consciousness. Sedation level can be measured with EEG monitoring with the bispectral index (BIS) monitor.

OBJECTIVES

To determine the feasibility and validity of BIS monitoring in terminally ill patients.

METHODS

In this prospective study, BIS registrations were performed in unconscious end-of-life patients admitted to a palliative care center. Validated scores were used to measure level of sedation (Ramsay score), pain (Numeric Rating Scale or Rotterdam Elderly Pain Observations Scale), delirium (Delirium Observation Screening score), and overall comfort (Numeric Rating Scale). Validity and sensitivity to change of BIS values were considered, and the effects of medication and the time till death on BIS values were evaluated in a linear mixed model analysis.

RESULTS

Fifty-eight patients were included for analysis. BIS monitoring was acceptable to patients, relatives, and medical staff. BIS values were moderately correlated with Ramsay scores (0.46) but were highly variable for deeply sedated patients. BIS values changed significantly before and after a midazolam dose (P < 0.001). Midazolam treatment resulted on average in a statistically significant reduction of the BIS values (-4.5, 95% CI -7.0 to -2.0), whereas morphine and haloperidol did not.

CONCLUSION

This is one of the first validation studies in which BIS monitoring in end-of-life patients is described. BIS monitoring is feasible in unconscious terminally ill patients. However, based on our results, the wide range of BIS values in deeply sedated and comfortable patients seems to hamper its use in daily clinical practice.

A Protocol for the Control of Agitation in Palliative Care

Background:

Agitation is a distressing and dangerous behavior for all involved.

Objective:

To study a protocol effectiveness and safety.

Methods:

The time when the protocol was initiated and when the agitation was controlled, the number of doses needed and the complications observed were recorded.

Results:

One hundred and thirty-five inpatients of a palliative care service were included. The most frequent diagnosis was head and neck cancer, 37 (27%). The protocol was used 584 times, from 1 to 31 times on each patient, median of 3 times. Five hundred and thirty-four (91%) agitation episodes were controlled with only the first dose of the protocol, without significant complications.

Conclusion:

From those results, it can be said that this protocol is effective and safe.

Subcutaneous fluid and drug delivery: safe, efficient and inexpensive

Patients with difficult venous access or oral intolerance and clinical situations with inadequate response to oral therapy have generated the need for alternative routes of delivery for drugs and fluids.

The purpose of this study was to conduct a systematic review examining the evidence for subcutaneous (SC) administration of drugs and/or fluids.

We used a broad search strategy using electronic databases CINAHL, EMBASE, PubMed and Cochrane library, key terms and ‘Medical Subject Headings’ (MeSH) such as ‘subcutaneous route’, ‘hypodermoclysis’ and the name/group of the most used drugs via this route (e.g. ‘ketorolac, morphine, ceftriaxone’, ‘analgesics, opioids, antibiotics’).

We conclude that the SC route is an effective alternative for rehydration in patients with mild–moderate dehydration and offers a number of potential advantages in appropriately selected scenarios. Experience of administering drugs by this route suggests that it is well tolerated and is associated with minimal side-effects.

Continuous infusions of midazolam and interrupted hydration - such as insulin infusions without glucose?

The Liverpool Care Pathway (LCP) for the dying patient is a UK care pathway covering palliative care options for patients in the final days or hours of life; it has recently been recommended for decommission in the UK following an independent review. The pathway was widely implemented in UK hospitals in part because of governmental financial incentives. One of the criticisms of the LCP included reports of the rapid escalation to continuous infusions of sedatives in patients who then became quickly unconscious and unable to communicate.

Characterization of mucoadhesive nasal gels containing midazolam hydrochloride prepared from Linum usitatissimum L. mucilage

Nasal drug delivery systems prepared from natural materials are gaining importance in the field of pharmaceutical technology. Mucilage isolated from Linum usitatissimum L. (LUM) seeds was reported to be an effective natural mucoadhesive agent. The present study deals with a comparison of various characteristics of nasal gels containing midazolam hydrochloride (HCl) prepared from mucoadhesive agent extracted from Linum usitatissimum L. seeds and synthetic polymers like HPMC and Carbopol 934P in terms of texture profile analysis, mucoadhesive strength, and in vivo drug absorption profiles. It was observed that gels formulated with the natural mucilage showed better results than the synthetic gels in all aspects like hardness, adhesiveness, cohesiveness and mucoadhesive strength. The absolute bioavailability of midazolam hydrochloride from the natural gel was 97.55% whereas that of synthetic gels was 57.33% and 76.81% respectively.

Development and characterization of mucoadhesive in situ nasal gel of midazolam prepared with Ficus carica mucilage

The objective of the present study was to prepare mucoadhesive in situ nasal gels with mucilage isolated from fig fruits (Ficus carica, family: Moraceae) containing midazolam hydrochloride. Nasal gels of midazolam were prepared using three different concentrations (0.5%, 1.0% and 1.5% w/v) of F. carica mucilage (FCM) and synthetic polymers (hydroxypropylmethyl cellulose and Carbopol 934). Evaluation of FCM showed that it was as safe as the synthetic polymers for nasal administration. In situ gels were prepared with mixture Pluronic F127 and mucoadhesive agents. Evaluation of the prepared gels was carried out, including determination of viscosity, texture profile analysis and mucoadhesive strength. In vitro drug permeation study was conducted with the gels prepared with and without permeation enhancer (0.5% w/v sodium taurocholate) using excised goat nasal mucosa. In vitro permeation profiles were evaluated, and histological study of nasal mucosae before and after permeation study was also conducted to determine histological change, if any. In vivo experiments conducted in rabbits further confirmed that in situ nasal gels provided better bioavailability of midazolam than the gels prepared from synthetic mucoadhesive polymers. It was observed that the nasal gel containing 0.5% FCM and 0.5% sodium taurocholate exhibited appropriate rheological, mechanical and mucoadhesive properties and showed better drug release profiles. Moreover, this formulation produced no damage to the nasal mucosa that was used for the permeation study, and absolute bioavailability was also higher compared to gels prepared from synthetic polymers.

[Usefulness of the subcutaneous route in the care of patients with advanced dementia]

In advanced dementia, the therapeutic goals should be patient comfort, adequate symptom control, and the prevention of suffering due to futile, intrusive or disproportionate procedures. To attain these goals, the subcutaneous route is a useful tool, since it allows fluid administration and the delivery of many drugs. Because it is well tolerated and easy to apply, this route can be safely used in non-hospital settings, allowing patients to stay in their environment and avoiding the risks resulting from hospitalization. Although subcutaneous administration is outside the approved label of many drugs, clinical experience and the medical literature have produced sound evidence that has been incorporated into a number of practice guidelines in palliative care. The recent regulations simplify the implementation of these standards of clinical practice.

Midazolam as adjunct therapy to morphine in the alleviation of severe dyspnea perception in patients with advanced cancer

The mainstay of dyspnea palliation remains altering its central perception. Morphine is the main drug and anxiolytics have a less established role. This trial assessed the role of midazolam as adjunct therapy to morphine in the alleviation of severe dyspnea perception in terminally ill cancer patients. One hundred and one patients with severe dyspnea were randomized to receive around-the-clock morphine (2.5 mg every 4 hours for opioid-naïve patients or a 25% increment over the daily dose for those receiving baseline opioids) with midazolam rescue doses (5 mg) in case of breakthrough dyspnea (BD) (Group Mo); around-the-clock midazolam (5 mg every 4 hours) with morphine rescues (2.5 mg) in case of BD (Group Mi); or around-the-clock morphine (2.5 mg every 4 hours for opioid-naïve patients or a 25% increment over the daily dose for those receiving baseline opioids) plus midazolam (5 mg every 4 hours) with morphine rescue doses (2.5 mg) in case of BD (Group MM). All drugs were given subcutaneously in a single-blinded way. Thirty-five patients were entered in Group Mo, 33 entered in Mi, and 33 entered in MM. At 24 hours, patients who experienced dyspnea relief were 69%, 46%, and 92% in the Mo, Mi, and MM groups, respectively (P = 0.0004 and P = 0.03 for MM vs. Mi and MM vs. Mo, respectively). At 48 hours, those with no dyspnea relief (no controlled dyspnea) were 12.5%, 26%, and 4% for the Mo, Mi, and MM groups, respectively (P = 0.04 for MM vs. Mi). During the first day, patients with BD for the groups Mo, Mi, and MM were 34.3%, 36.4%, and 21.2%, respectively (P = NS or not significant), whereas during the second day, these percentages were 38%, 38.5%, and 24%, respectively (P = NS). The data demonstrate that the beneficial effects of morphine in controlling baseline levels of dyspnea could be improved with the addition of midazolam to the treatment.

In vivo measurements of T1 relaxation times in mouse brain associated with different modes of systemic administration of manganese chloride

PURPOSE

To measure regional T1 and T2 values for normal C57Bl/6 mouse brain and changes in T1 after systemic administration of manganese chloride (MnCl2) at 9.4 T.

MATERIALS AND METHODS

C57Bl/6 mice were anesthetized and baseline T1 and T2 measurements obtained prior to measurement of T1 after administration of MnCl2 at 9.4 T. MnCl2 was administered systemically either by the intravenous (IV), intraperitoneal (IP), or subcutaneous (SC) routes. T1 and T2 maps for each MRI transverse slice were generated using commercial software, and T1 and T2 values of white matter (WM), gray matter (GM), pituitary gland, and lateral ventricle were obtained.

RESULTS

When compared with baseline values at low-field, significant lengthening of the T1 values was shown at 9.4 T, while no significant change was seen for T2 values. Significant T1 shortening of the normal mouse brain was observed following IV, IP, and SC administration of MnCl2, with IV and IP showing similar acute effects. Significant decreases in T1 values were seen for the pituitary gland and the ventricles 15 minutes after either IV or IP injection. GM showed greater uptake of the contrast agent than WM at 15 and 45 minutes after either IV or IP injections. Although both structures are within the blood-brain barrier (BBB), GM and WM revealed a steady decrease in T1 values at 24 and 72 hours after MnCl2 injection regardless of the route of administration.

CONCLUSION

Systemic administration of MnCl2 by IV and IP routes induced similar time-course of T1 changes in different regions of the mouse brain. Acute effects of MnCl2 administration were mainly influenced by either the presence or absence of BBB. SC injection also provided significant T1 change at subacute stage after MnCl2 administration.