Effectiveness and safety of low-dose versus standard-dose rivaroxaban and apixaban in patients with atrial fibrillation

BACKGROUND

Low-dose direct oral anticoagulant (DOAC) use is quite prevalent in clinical practice, but evidence of its effectiveness and safety compared with high-dose DOAC in patients with atrial fibrillation (AF) remains limited. We aimed to assess the effectiveness and safety of low-dose and high-dose DOACs in patients with AF with similar baseline characteristics.

METHODS

We used a cohort of hospitalized patients with a primary or secondary diagnosis of AF after discharge to the community, whose data were stored in the Quebec administrative databases, from 2011 to 2017. Older adults with AF newly prescribed with rivaroxaban (15 or 20 mg) or apixaban (2.5 mg or 5 mg) were classified as under treatment (UT) and intent to treat (ITT). We used an inverse probability treatment weighting study of new users of rivaroxaban and apixaban to address confounding by indication. The primary effectiveness outcome was ischemic stroke/systemic embolism (SE), while the primary safety outcome was major bleeding (MB). We used Cox proportional models to estimate the marginal hazard ratios (HRs).

FINDINGS

A total of 1,722 and 4,639 patients used low-dose and standard-dose rivaroxaban, respectively, while 3,833 and 6,773 patients used low-dose and standard-dose apixaban, respectively. No significant difference was observed in the incidence of comparative stroke/SE and MB between low-dose and standard-dose rivaroxaban, except for the risk of acute myocardial infarction (AMI), which was increased with the low dose in the UT analysis. For apixaban, no difference was found in the bleeding rates, but the risk of stroke/SE (HR: 1.95; 95% confidence interval (CI): 1.38-2.76) and death (HR: 1.99; 95% CI: 1.46-2.70) were greater in the low-dose group than in the standard-dose group in the UT analysis. Similar results were observed for the ITT analysis.

CONCLUSION

No significant differences were observed in the effectiveness or safety outcome between low-dose and standard-dose rivaroxaban, except for AMI. However, low-dose apixaban was associated with a greater risk of stroke/SE and death without a reduction in the bleeding rates.

Comparative Effectiveness and Safety of Low-Dose Oral Anticoagulants in Patients With Atrial Fibrillation

Aims: Observational studies of various dose levels of direct oral anticoagulants (DOACs) for patients with atrial fibrillation (AF) found that a high proportion of patients received a dose lower than the target dose tested in randomized controlled trials. There is a need to compare low-dose DOACs with warfarin or other DOACs on effectiveness and safety. Methods: Using administrative data from Quebec province, Canada, we built a cohort of new warfarin or DOAC users discharged from hospital between 2011 and 2017. We determined CHA₂DS₂-VASc and HAS-BLED scores, and comorbidities for 3-year prior cohort entry. The primary effectiveness endpoint was a composite of ischemic stroke/systemic embolism (SE), and secondary outcomes included a safety composite of major bleeding (MB) events and effectiveness composite (stroke/SE, death) at 1-year follow-up. We contrasted each low-dose DOAC with warfarin or other DOACs as references using inverse probability of treatment weighting to estimate marginal Cox hazard ratios (HRs). Results: The cohort comprised 22,969 patients (mean age: 80-86). We did not find a significant risk reduction for the stroke/SE primary effectiveness endpoint for DOACs vs. warfarin; however, we observed a significantly lower risk for low-dose dabigatran vs. warfarin (HR [95%CI]: 0.59 [0.42-0.81]) for effectiveness composite, mainly due to a lower death rate. The differences in effectiveness and safety composites between low-dose rivaroxaban vs. warfarin were not significant. However, low-dose apixaban had a better safety composite (HR: 0.68 [0.53-0.88]) vs. warfarin. Comparisons of dabigatran vs. apixaban showed a lower risk of stroke/SE (HR: 0.53 [0.30-0.93]) and a 2-fold higher risk of MB. The MB risk was higher for rivaroxaban than for apixaban (HR: 1.58 [1.09-2.29]). Conclusions: The results of this population-based study suggest that low-dose dabigatran has a better effective composite than warfarin. Compared with apixaban, low-dose dabigatran had a better effectiveness composite but a worse safety profile. Low-dose apixaban had a better safety composite than warfarin and other low-dose DOACs. Given that the comparative effectiveness and safety seem to vary from one DOAC to another, pharmacokinetic data for specific populations are now warranted.

Comparative effectiveness and safety of high-dose rivaroxaban and apixaban for atrial fibrillation: A propensity score-matched cohort study

STUDY OBJECTIVE

Observational studies assessing direct oral anticoagulant (DOACs) dosage in atrial fibrillation (AF) reported that a lower proportion of patients received high-dose DOACs compared to those in randomized controlled trials (RCTs). Effectiveness and safety of high-dose DOACs relative to apixaban in a real-world AF population need to be addressed. The aim is to assess comparative effectiveness and safety of high-dose rivaroxaban relative to apixaban.

DESIGN

We conducted a cohort study. Setting We built a cohort of patients hospitalized and discharged in community with a primary or secondary AF diagnosis from 2011-2017 using Quebec administrative databases (Med-Echo and RAMQ). Patients Cohort entry was defined as the first OAC claim in new users of high-dose rivaroxaban and apixaban, with no OAC claims in the prior year. Intervention To compare effectiveness and safety of high-dose rivaroxaban to apixaban. Measurement We ascertained patient demographics, comorbidities, CHA2DS2-VASc and HASBLED scores and Charlson score within 3 years prior to cohort entry. Primary effectiveness and safety were a composite of ischemic stroke/systemic thrombosis, death, myocardial infarction, and of intracranial bleeding (ICH), extracranial major bleeding, in the first year following drug initiation. We conducted propensity score matching and estimated hazard ratios (HRs) for outcomes using Cox proportional hazard models. All the analyses were conducted to account for competing risks. Main results The cohort consisted of 4,632 and 6,771 patients received high-dose rivaroxaban and apixaban, respectively. High-dose rivaroxaban users were younger with a mean age of 73.2 years, presented less associated comorbidities and had lower CHA2DS2-VASc scores compared to apixaban. High-dose rivaroxaban at the intention to treat was associated with a higher risk of stroke/SE/death (HR 1.21, 95% CI 1.04-1.40) and worse composite effectiveness (HR 1.21: 1.05-1.40); under treatment exposure, those values were at HR (1.66: 1.21-2.29) and HR (1.58:1.19-2.10), respectively. And, rivaroxaban presented a less favorable safety profile relative to apixaban. Conclusion In this study, composite effectiveness and safety varied between rivaroxaban and apixaban. High-dose apixaban was observed to have a better effectiveness and safety.

Agreement Between Administrative Database and Medical Chart Review for the Prediction of Chronic Kidney Disease G category

Background

Chronic kidney disease (CKD) is a major health issue and cardiovascular risk factor. Validity assessment of administrative data for the detection of CKD in research for drug benefit and risk using real-world data is important. Existing algorithms have limitations and we need to develop new algorithms using administrative data, giving the importance of drug benefit/risk ratio in real world.

Objective

The aim of this study was to validate a predictive algorithm for CKD GFR category 4-5 (eGFR < 30 mL/min/1.73 m² but not receiving dialysis or CKD G4-5ND) using the administrative databases of the province of Quebec relative to estimated glomerular filtration rate (eGFR) as a reference standard.

Design

This is a retrospective cohort study using chart collection and administrative databases.

Setting

The study was conducted in a community outpatient medical clinic and pre-dialysis outpatient clinic in downtown Montreal and rural area.

Patients

Patient medical files with at least 2 serum creatinine measures (up to 1 year apart) between September 1, 2013, and June 30, 2015, were reviewed consecutively (going back in time from the day we started the study). We excluded patients with end-stage renal disease on dialysis. The study was started in September 2013.

Measurement

Glomerular filtration rate was estimated using the CKD Epidemiological Collaboration (CKD-EPI) from each patient's file. Several algorithms were developed using 3 administrative databases with different combinations of physician claims (diagnostics and number of visits) and hospital discharge data in the 5 years prior to the cohort entry, as well as specific drug use and medical intervention in preparation for dialysis in the 2 years prior to the cohort entry.

Methods

Chart data were used to assess eGFR. The validity of various algorithms for detection of CKD groups was assessed with sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

Results

A total of 434 medical files were reviewed; mean age of patients was 74.2 ± 10.6 years, and 83% were older than 65 years. Sensitivity of algorithm #3 (diagnosis within 2-5 years and/or specific drug use within 2 years and nephrologist visit ≥4 within 2-5 years) in identification of CKD G4-5ND ranged from 82.5% to 89.0%, specificity from 97.1% to 98.9% with PPV and NPV ranging from 94.5% to 97.7% and 91.1% to 94.2%, respectively. The subsequent subgroup analysis (diabetes, hypertension, and <65 and ≥65 years) and also the comparisons of predicted prevalence in a cohort of older adults relative to published data emphasized the accuracy of our algorithm for patients with severe CKD (CKD G4-5ND).

Limitations

Our cohort comprised mostly older adults, and results may not be generalizable to all adults. Participants with CKD without 2 serum creatinine measurements up to 1 year apart were excluded.

Conclusions

The case definition of severe CKD G4-5ND derived from an algorithm using diagnosis code, drug use, and nephrologist visits from administrative databases is a valid algorithm compared with medical chart reviews in older adults.

Anticoagulants in Older Patients with Nonvalvular Atrial Fibrillation after Intracranial Hemorrhage

Background and Purpose

Patients with nonvalvular atrial fibrillation (NVAF) who survive an intracranial hemorrhage (ICH) have an increased risk of ischemic stroke and systemic embolism (IS/ SE). We investigated whether starting oral anticoagulants (OACs) among older NVAF patients after an ICH was associated with a lower risk of IS/SE and mortality but offset by an increase in major bleeding.

Methods

We assembled a patient cohort from the Quebec Régie de l’Assurance Maladie du Québec (RAMQ) and Med-Echo administrative databases. We identified older adults with NVAF from 1995 to 2015. All patients with incident ICH and discharged in community were included. Patients were categorized according to OAC exposure. Outcomes included IS/SE, all-cause mortality, recurrent ICH and major bleeding after a quarantine period of 6 weeks. Crude event rates were calculated at 1-year of follow-up, and Cox proportional hazard models with a time-dependent binary exposure were used to assess adjusted hazard ratios (AHRs).

Results

The cohort of 683 NVAF patients with ICH aged 83 years on average. The rates (per 100 person-years) for IS/SE, death, ICH and major bleeding were 3.3, 40.6, 11.4, and 2.7 for the no OAC group; and 2.6, 16.3, 5.2, and 5.2 for OAC group, respectively. The AHR for IS/SE and death was 0.10 (95% confidence interval [CI], 0.05 to 0.21), 0.43 (95% CI, 0.19 to 0.97) for recurrent ICH and 1.73 (95% CI, 0.71 to 4.20) for major extracranial bleeding comparing OAC exposure to non-exposed.

Conclusions

Initiating OAC after ICH in older individuals with NVAF is associated with a reduction of IS/SE and mortality and a trend in recurrent ICH supporting its use after ICH.

Is there a potential association between spironolactone and the risk of new-onset diabetes in a cohort of older patients with heart failure?

PURPOSE

Some evidence suggests that spironolactone may have a deleterious effect on glucose homeostasis. The objective of this study was to assess whether spironolactone use is associated with a higher risk of developing diabetes in a large cohort of patients with heart failure (HF).

METHODS

Two Quebec government administrative databases were used to identify a cohort of hospitalized patients discharged between January 1995 and December 2009 with a primary discharge diagnosis of HF and without secondary discharge diagnosis of diabetes. Patients were categorized as new users of spironolactone and non-users. The primary outcome was defined as new-onset diabetes (NOD) during 5 years of follow-up and was ascertained using ICD codes for diabetes or use of hypoglycemic agents.

RESULTS

Among the 2974 patients that were included in the cohort analysis, 769 were given a new prescription of spironolactone. The incidence rate of NOD was similar among spironolactone users (5.0 per 100 person-years) and non-users (4.9 per 100 person-years). There was no significant association between the use of spironolactone and NOD in the crude, unadjusted model (hazard ratio (HR) 1.01; 95% confidence interval (CI) 0.80-1.28; p = 0.9217), and it remained unchanged in the adjusted Cox proportional hazard model (HR = 0.92; 95% CI = 0.72-1.18; p = 0.5227). The results were consistent with those observed in sensitivity analyses of a 1:3 propensity score-matched cohort (HR = 0.97; CI = 0.76-1.25; p = 0.8169).

CONCLUSION

We found no evidence supporting the claim that use of spironolactone is associated with a higher risk of diabetes among patients hospitalized for HF.

Development of Quality Indicators to Assess Oral Anticoagulant Management in Community Pharmacies for Patients with Atrial Fibrillation

BACKGROUND

Few studies have evaluated the quality of oral anticoagulant management by community pharmacists. There is no complete set of quality indicators available for this purpose.

OBJECTIVE

To develop a set of specific quality indicators to assess oral anticoagulant management by community pharmacists for patients with atrial fibrillation (AF).

METHODS

Quality indicators were developed in 3 phases. In phase 1, potential quality indicators were generated based on clinical guidelines and a literature review. In phase 2, a modified RAND appropriateness method involving 2 rounds was implemented with 9 experts, who judged the appropriateness of quality indicators generated in phase 1 based on the extent to which they were accurate, based on evidence, relevant, representative of best practices, and measurable in community pharmacies. Phase 3 consisted of a feasibility assessment in 5 community pharmacies on 2 patients each.

RESULTS

The final set included 38 quality indicators grouped into 6 categories: documentation (n = 29), risk assessment (n = 3), clinical control (n = 1), clinical follow-up (n = 15), choice of therapy (n = 11), and interaction management (n = 8). The quality indicators referred to process of care (n = 34), clinical outcomes (n = 2), or structure of care (n = 2). There were 24 quality indicators related to vitamin K antagonists (VKAs), and 17 were related to direct oral anticoagulants (DOACs). To assess quality indicators, a questionnaire was developed for completion by community pharmacists for each patient, which included 17 questions about VKA patients and 12 questions about DOAC patients.

CONCLUSIONS

A first set of quality indicators is now available to assess the quality of oral anticoagulant management by community pharmacists for patients with AF.

DISCLOSURES

This research was supported by the Réseau Québécois de recherche sur le médicament (RQRM); the Blueprint for Pharmacy in collaboration with Pfizer Canada; and the Cercle du Doyen of the Faculty of Pharmacy, University of Montreal. The study sponsors were not involved in the study design, data collection, data interpretation, the writing of the article, or the decision to submit the report for publication. Chartrand received a scholarship from the Fonds de Recherche du Québec en Santé (FRQ-S), the Réseau Québécois de recherche sur l'usage des médicaments with Pfizer, and the Faculty of Pharmacy, University of Montreal. Guénette holds a Junior-1 Clinician Researcher Award from the FRQ-S in partnership with the Société québécoise d'hypertension artérielle. Williamson holds a Junior-1 Career Award from the FRQ-S. Côté reported being a medical speaker for Bayer, Boehringer Ingelheim Canada, and Pfizer Canada. The other authors reported no conflicts of interest. Study concept and design were contributed by Lalonde, Chartrand, and Martin. Chartrand, Martin, and Lalonde collected the data, along with Brouillette, Côté, Huot, Landry, Martineau, Perreault, Williamson, and White-Guay. Data interpretation was performed by Chartrand, Gagnon, and Lalonde, along with Guénette and Martin. The manuscript was primarily written by Chartrand, along with Guénette and Lalonde, and revised by Chartrand, Guénette, and Lalonde, along with the other authors. A portion of this study's results was presented at the 4th RQRM Annual Meeting on September 22-23, 2014, in Orford, Quebec, Canada, in the form of an abstract, which was published in the Journal of Population Therapeutics and Clinical Pharmacology, 2014;21(2):e312.

Association Between Metformin Adherence and All-Cause Mortality Among New Users of Metformin: A Nested Case-Control Study

BACKGROUND

Metformin presents better survival rates than other oral antidiabetics in the treatment of type 2 diabetes. However, these benefits may be dampened by inadequate treatment adherence.

OBJECTIVE

We aimed to investigate the relationship between adherence level to metformin therapy and all-cause mortality over 10 years in incident metformin users.

METHODS

A nested case-control study was conducted using a large cohort of beneficiaries of the Quebec public drug insurance plan, aged 45 to 85 years, who initiated metformin between 2000 and 2009. Each case of all-cause death during follow-up was matched with up to 10 controls. Adherence to metformin was measured using the medication possession ratio (MPR). Conditional logistic regression models were used to estimate rate ratios (RRs) for mortality between adherent (MPR ≥ 80%) and nonadherent patients (MPR < 80%). Subgroup analyses were conducted according to age (45-64 and 65-85 years) and comedication use (antihypertensive/cardiovascular drugs and statins).

RESULTS

The cohort included 82 720 incident metformin users, followed up for 2.4 [0.8-4.4] years (median [interquartile range]) and 4747 cases of all-cause deaths. Analyses revealed decreased mortality risks after long-term adherence to metformin. Specifically, RRs were 0.84 (95% CI = [0.71-0.98]) and 0.69 [0.57-0.85] after 4 to 6 and ≥6 years of adherence to metformin, respectively. Survival benefits of long-term adherence (≥4 years) were also observed across most subgroups and particularly in patients using neither antihypertensive/cardiovascular drugs nor statins (0.57 [0.41-0.77]).

CONCLUSIONS

Long-term adherence to metformin is associated with decreased risks of all-cause mortality in incident metformin users. Further research should investigate whether survival benefits vary according to the comorbidity burden of patients.

Older adults with heart failure treated with carvedilol, bisoprolol, or metoprolol tartrate: risk of mortality

PURPOSE

The long-term use of β-blockers has been shown to improve clinical outcomes among patients with heart failure (HF). However, a lack of data persists in assessing whether carvedilol or bisoprolol are superior to metoprolol tartrate in clinical practice. We endeavored to compare the effectiveness of β-blockers among older adults following a primary hospital admission for HF.

METHODS

We conducted a cohort study using Quebec administrative databases to identify patients who were using β-blockers, carvedilol, bisoprolol, or metoprolol tartrate after the diagnosis of HF. We characterized the patients by the type of β-blocker prescribed at discharge of their first HF hospitalization. An adjusted multivariate Cox proportional hazards model was used to compare the primary outcome of all-cause mortality. We also conducted analyses by matching for a propensity score for initiation of β-blocker therapy and assessed the effect on primary outcome.

RESULTS

Among 3197 patients with HF with a median follow-up of 2.8 years, the crude annual mortality rates (per 100 person-years) were at 16, 14.9, and 17.7 for metoprolol tartrate, carvedilol, and bisoprolol, respectively. Adjusted hazard ratios of carvedilol (hazard ratio 0.92; 0.78-1.09) and bisoprolol (hazard ratio 1.04; 0.93-1.16) were not significantly different from that of metoprolol tartrate in improving survival. After matching for propensity score, carvedilol and bisoprolol showed no additional benefit with respect to all-cause mortality compared with metoprolol tartrate.

CONCLUSIONS

Our evidence suggests no differential effect of β-blockers on all-cause mortality among older adults with HF. Copyright © 2016 John Wiley & Sons, Ltd.

Persistence and adherence to oral antidiabetics: a population-based cohort study

AIMS

A population-based cohort study design was used to estimate persistence rate, re-initiation rate after discontinuation, and adherence level among incident users of oral antidiabetics (OADs), and to investigate predictors of non-persistence and non-adherence.

METHODS

Incident OAD users were identified using healthcare databases of residents covered by the public drug insurance plan of the Province of Quebec, Canada. Patients initiated OAD therapy between January 2000 and October 2009 and were aged 45-85 years at cohort entry. Persistence rate, re-initiation after discontinuation, and adherence level were assessed over 2 years. Predictors of non-persistence and non-adherence were analyzed using Cox and logistic regression models, respectively.

RESULTS

The cohort included 160,231 incident OAD users at entry. One year after OAD initiation, persistence rate was 51 % and adherence level 67 %. Among those deemed non-persistent, 80.6 % re-initiated OAD therapy within 12 months of discontinuation; a proportion increasing with primary persistence duration. The 1-year persistence rate varied according to OAD classes; being the highest for thiazolidinediones (62 %) and the lowest for alpha-glucosidase inhibitors (30 %). The likelihood for non-persistence was 39-54 % higher when drug copayments were required. Conversely, OAD discontinuation was least likely for patients with schizophrenia [hazard ratio 0.70 (95 % CI 0.67-0.73)], dyslipidemia [0.85 (0.84-0.87)], anticoagulation [0.86 (0.83-0.88)], hypertension [0.87 (0.85-0.88)], and ≥7 medications [0.90 (0.88-0.91)]. Predictors of non-adherence were similar.

CONCLUSIONS

Non-persistence and non-adherence to OAD therapy were common, although re-initiation rate was high. OAD classes, drug copayments, comorbidities and co-medications may help identifying those who were more likely to benefit from counseling.

Adherence to antihypertensive agents improves risk reduction of end-stage renal disease

Uncontrolled hypertension is associated with an increased risk of end-stage renal disease (ESRD). Intensified blood pressure control may slow progression of chronic kidney disease; however, the impact of antihypertensive agent adherence on the prevention of ESRD has never been evaluated. Here we assessed the impact of antihypertensive agent adherence on the risk of ESRD in 185,476 patients in the RAMQ databases age 45 to 85 and newly diagnosed/treated for hypertension between 1999 and 2007. A case cohort study design was used to assess the risk of and multivariate Cox proportional models were used to estimate the adjusted hazard ratio of ESRD. Adherence level was reported as a medication possession ratio. Mean patient age was 63 years, 42.2% male, 14.0% diabetic, 30.3% dyslipidemic, and mean follow-up was 5.1 years. A high adherence level of 80% or more to antihypertensive agent(s) compared to a lower one was related to a risk reduction of ESRD (hazard ratio 0.67; 95% confidence intervals 0.54-0.83). Sensitivity analysis revealed that the effect is mainly in those without chronic kidney disease. Risk factors for ESRD were male, diabetes, peripheral artery disease, chronic heart failure, gout, previous chronic kidney disease, and use of more than one agent. Thus, our study suggests that a better adherence to antihypertensive agents is related to a risk reduction of ESRD and this adherence needs to be improved to optimize benefits.

Adherence to antihypertensive agents after ischemic stroke and risk of cardiovascular outcomes

OBJECTIVE

To evaluate the relationship between antihypertensive (AH) drug adherence and cardiovascular (CV) outcomes among patients with a recent ischemic stroke and assess the validity of our approach.

METHODS

A cohort of 14,227 patients diagnosed with an ischemic stroke was assembled from individuals 65 years and older who were treated with AH agents from 1999 to 2007 in Quebec, Canada. A nested case-control design was used to evaluate the occurrence of nonfatal major CV outcomes and mortality. Each case was matched to 15 controls by age and cohort entry time. Medication possession ratio was used for AH agent adherence level. Adjusted conditional logistic regression models were used to estimate the rate ratio of CV events. The validity of the approach was assessed by evaluating the adherence level of CV-protective and non-CV-protective drugs.

RESULTS

Mean age was 75 years, 54% were male, 38% had coronary artery disease, 23% had diabetes, 47% dyslipidemia, and 14% atrial fibrillation or flutter. High adherence to AH therapy was mirrored by similar adherence to statins and antiplatelet agents and was associated with a lower risk of nonfatal vascular events compared with lower adherence (rate ratio 0.77 [0.70-0.86]). We observed a paradoxic link between adherence to several drugs and all-cause mortality.

CONCLUSION

Adherence to AH agents is associated with adherence to other secondary preventive therapies and a risk reduction for nonfatal vascular events after an ischemic stroke. Overestimation of all-cause mortality reduction may be related to frailty and comorbidities, which may confound the apparent benefit of different drugs.

Some synaptic inputs and ascending projections of lateralis posterior thalamic neurons

(1) Some synaptic inputs and telencephalic targets of lateralis intermedius-lateralis posterior (LI-LP) thalamic neurons have been investigated in the encéphale isolé cat by recording extracellular unit discharges and focal slow waves following stimulation of cortical areas 5 and 7, center median (CM) thalamic nucleus and mesencephalic reticular formation (RF). (2) Orthodromic and/or antidromic discharges in LI-LP neurons following anterior suprasylvian stimulation are electrophysiological evidence of thalamocortical reciprocal pathway in this "association" system. A few neurons were backfired from several cortical stimulated foci at different latencies, thus suggesting the existence of LI-LP output cells with branching axons. The numerous cases of cortically elicited synaptic excitation in LI-LP cells, taken together with evidence of an unexpectedly high proportion of corticothalamic neurons found in parallel experiments of this laboratory on areas 5 and 7, support the suggestion that complex functions of the "association" cortex partially depend on its downstrem connections with thalamic integrative structures. (3) Monosynaptic and oligosynaptic excitatory projections link the brain stem reticular core with LI-LP nuclear group. For some neurons, this is a high-security pathway as shown by the ability of thalamic cells to follow at short latencies fast repetitive reticular shocks. The RF-elicited phasic excitation is followed by a period of suppressed spontaneous and evoked discharge. The excitatory projections from the upper brain stem RF to the LI-LP nuclei are discussed in relation to disfacilitatory phenomena in thalamocortical systems due to withdrawal of reticulofugal ascending activation at sleep onset.