Respiratory effects of baclofen and 3-aminopropylphosphinic acid in guinea-pigs

The safety of benzodiazepines and related drugs during pregnancy: an updated meta-analysis of cohort studies

PURPOSE

The prevalence of benzodiazepines and related drugs (BZRDs) use during pregnancy increased sharply in recent years. Thus, there are concerns regarding the pregnancy outcomes following exposure to BZRDs.

METHODS

Two electronic databases were thoroughly searched to identify related clinical studies published from inception until June 2023. English-language cohort studies with high-quality comparing antenatal BZRDs exposure to an unexposed group on any delivery outcome were included.

RESULTS

Ten cohort studies that estimated adverse neonatal outcomes associated with exposure to BZRDs during pregnancy were included. Exposure to BZRDs during pregnancy was associated with an increased risk of congenital malformation [odds ratio (OR) 1.09, 95% confidence interval (CI) 1.05-1.13, p < 0.001], heart malformation (OR 1.13, 95% CI 1.04-1.22, p = 0.003), preterm birth (OR 1.45, 95% CI 1.23-1.7, p < 0.001), SGA (OR 1.18, 95% CI 1.08-1.29, P < 0.001), LBW (OR 1.42, 95% CI 1.25-1.6, p = 0.001) or low Apgar score (OR 1.42, 95% CI 1.08-1.87, p = 0.011),compared with no exposure. Further analyses limited to the first trimester exposure yielded consistent results.

CONCLUSIONS

Exposure to BZRDs during pregnancy may be associated with several adverse neonatal outcomes. However, we could not rule out the potential indication confounding factor, further studies with high-quality that control for important confounders are still needed to verify our findings.

Asthma and chronic obstructive pulmonary disease (COPD) in people with multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Studies have found that multiple sclerosis (MS) has an impact on the initiation or the course of asthma and chronic obstructive pulmonary disease (COPD). This review amied to investigate the prevalence and odds of asthma and COPD among people with MS (pwMS).

METHOD

PubMed, Embase, Scopus, and Web of Science were systemically searched from inception to May 2023. R version 4.3.2 and random-effect model were used to calculate the pooled prevalence and odds ratio (OR), with their 95 % confidence interval (CI), in pwMS.

RESULTS

A total of 40 studies consisting of 287,702 pwMS were included. 37 studies indicated that the pooled prevalences of asthma and COPD among pwMS were 5.97 % (95 % CI: 4.62 %-7.69 %, I2=99 %) and 3.03 % (95 % CI: 1.82 %-5.00 %, I2=99 %), respectively. 24 studies on 236,469 pwMS and 85,328,673 healthy controls revealed that the overall odds of asthma and COPD in MS were 1.14 (95 % CI: 0.76-1.71, p-value=0.53, I2=97 %) and 1.28 (95 % CI: 1.11-1.47, p-value<0.01, I2=70 %), respectively.

CONCLUSION

MS can increased the risk of developing COPD, while asthma does not exhibit a significant relationship with MS. Our study highlights the importance of identifying pwMS who face greater risks of respiratory issues to monitor efficiently and initiate suitable preventative actions.

Baclofen (fun drug) and ethanol combined poisoning in humans: A histopathology and morphometry model

BACKGROUND

- This study intends to address the scarcity of data regarding the pathogenesis of Baclofen poisoning in humans, which has seen a recent increase, worldwide, especially amongst the young people. Another reason for the conduction of this study was lack of the substantial data about the histo-pathological findings of lungs, in synergistic toxicity of Baclofen with Ethanol, in-spite of it being very common in humans, and both being respiratory depressant with similar mechanism of action.

PURPOSE

- The authors aimed to understand the pathogenesis of fatal poisonings in humans due to Baclofen in combination with Ethanol via an animal research model. The enhancement of the overall scientific literature by extending research along the lines of the handful studies available in this regard was another adjunct goal of the study.

MATERIAL AND METHODS

Fifteen Wistar rats were divided into control and test group of five and ten subjects respectively. The test group was further divided into two sub-groups of five each, with Baclofen administered to one, and it in conjunction with Ethanol to the other, in lowest dosages adjusted for the humans. Rats in both the groups were euthanized by dislocation of the cervical vertebrae for the histopathology examination.

RESULTS

Capillary and venous plethora, hemorrhages in the inter-alveolar septi, hemorrhages into the alveoli and sludging was seen in the 1st sub-group. The plethora of venules, capillaries and arterioles, with sludging by the WBC (white blood corpuscle) infiltrates was seen in the 2nd sub-group. Desquamation of the ciliated epithelium and edematous thickening of the intra-alveolar septi, along with features suggestive of the peri-vascular edema was seen in the 2nd sub-group. The morphometric analysis of the micro vessels showed a significantly higher value of the arteriolar diameter in the 2nd sub-group, in comparison to 1st, but the venular diameter in the two sub-groups did not differ to any extent.

Baclofen destabilises breathing during sleep in healthy humans: A randomised, controlled, double-blind crossover trial

AIMS

Periodic breathing is frequent in patients with severe heart failure. Apart from being an indicator of severity, periodic breathing has its own deleterious consequences (sleep-related oxygen desaturations, sleep fragmentation), which justifies attempts to correct it irrespective of the underlying disease. Animal models and human data suggest that baclofen can reconfigure respiratory central pattern generators. We hypothesised that baclofen, a GABA_B agonist, may thus be able to correct periodic breathing in humans.

METHODS

Healthy volunteers were exposed to hypoxia during sleep. Participants who developed periodic breathing (n = 14 [53 screened]) were randomly assigned to double-blind oral baclofen (progressively increased to 60 mg/d) or placebo. The primary outcome was the coefficient of variation (CoVar) of respiratory cycle total time considered as an indicator of breathing irregularity. Secondary outcomes included the CoVar of tidal volume, apnoea-hypopnoea index, sleep fragmentation index and ventilatory complexity (noise limit).

RESULTS

The analysis was conducted in 9 subjects after exclusion of incomplete datasets. CoVar of respiratory cycle total time significantly increased with baclofen during non-rapid eye movement sleep (median with placebo 56.00% [37.63-78.95]; baclofen 85.42% [68.37-86.40], P = .020; significant difference during the N1-N2 phases of sleep but not during the N3 phase). CoVar of tidal volume significantly increased during N1-N2 sleep. The apnoea-hypopnoea index, sleep fragmentation index and ventilatory complexity were not significantly different between placebo and baclofen.

CONCLUSION

Baclofen did not stabilise breathing in our model. On the contrary, it increased respiratory variability. Baclofen should probably not be used in patients with or at risk of periodic breathing.

The mechanisms of sudden-onset type adverse reactions to oseltamivir

Oseltamivir is contraindicated for people aged 10-19 in principle in Japan, due to concern about abnormal behaviours. Sudden death is another concern. This review examines growing evidence of their association and discusses underlying mechanisms of these sudden-onset type reactions to oseltamivir. First, the importance of animal models and the concept of human equivalent dose (HED) is summarized. Second, the specific condition for oseltamivir use, influenza infection, is reviewed. Third, findings from toxicity studies conducted prior to and after the marketing of oseltamivir are reported on to provide context on the observation of a possible causal association. Fourth, similarity and consistency of toxicity in humans with that in other animals is described. Finally, coherence of toxicokinetic and molecular level of evidence (channels, receptors and enzymes), including differences from the toxicity of other neuraminidase inhibitors, is reviewed. It is concluded that unchanged oseltamivir has various effects on the central nervous system (CNS) that may be related to clinical findings including hypothermia, abnormal behaviours including with fatal outcome, and sudden death. Among receptors and enzymes related to CNS action, it is known that oseltamivir inhibits nicotinic acetylcholine receptors, which are closely related to hypothermia, as well as human monoamine oxidase-A (MAO-A), which is closely related to abnormal or excitatory behaviours. Receptors such as GABAA , GABAB and NMDA and their related receptors/channels including Na+ and Ca2+ channels are thought to be other candidates for investigation related to respiratory suppression followed by sudden death and psychotic reactions (both acute and chronic), respectively.

Influence of baclofen on laryngeal and spinal motor drive during cough in the anesthetized cat

OBJECTIVES/HYPOTHESIS

The antitussive properties of (±) baclofen on laryngeal muscle activities have not been determined. The hypothesis of this study was that administration of (±) baclofen would suppress upper airway muscle motor activity in a dose-dependent manner during cough.

STUDY DESIGN

This is a prospective, preclinical, hypothesis-driven, paired design.

METHODS

Electromyograms of the parasternal, rectus abdominis, thyroarytenoid, posterior cricoarytenoid, and thyrohyoid were measured, along with esophageal pressure. Cough was elicited by mechanical stimulation of the lumen of the intrathoracic trachea in spontaneously breathing cats.

RESULTS

Baclofen (±) (3-10 μg kg(-1) i.a.) induced decreases in the electromyogram amplitude of the rectus abdominis motor drive during coughing, the inspiratory and active expiratory (E1) phases of cough, and cough number per epoch. There was no effect of (±) baclofen on the EMG amplitudes of any of the laryngeal muscles, the parasternal, or the duration of the passive expiratory (E2) phase.

CONCLUSIONS

Results from the present study indicate differential control mechanisms for laryngeal and inspiratory motor drive during cough, providing evidence of a control system regulating laryngeal activity and inspiratory spinal drive that is divergent from the control of expiratory spinal motoneurons.

Different in vitro and in vivo profiles of substituted 3-aminopropylphosphinate and 3-aminopropyl(methyl)phosphinate GABA(B) receptor agonists as inhibitors of transient lower oesophageal sphincter relaxation

BACKGROUND AND PURPOSE

Gastro-oesophageal reflux is predominantly caused by transient lower oesophageal sphincter relaxation (TLOSR) and GABA(B) receptor stimulation inhibits TLOSR. Lesogaberan produces fewer CNS side effects than baclofen, which has been attributed to its affinity for the GABA transporter (GAT), the action of which limits stimulation of central GABA(B) receptors. To understand the structure-activity relationship for analogues of lesogaberan (3-aminopropylphosphinic acids), and corresponding 3-aminopropyl(methyl)phosphinic acids, we have compared representatives of these classes in different in vitro and in vivo models.

EXPERIMENTAL APPROACH

The compounds were characterized in terms of GABA(B) agonism in vitro. Binding to GATs and cellular uptake was done using rat brain membranes and slices respectively. TLOSR was measured in dogs, and CNS side effects were evaluated as hypothermia in mice and rats.

KEY RESULTS

3-Aminopropylphosphinic acids inhibited TLOSR with a superior therapeutic index compared to 3-aminopropyl(methyl)phosphinic acids. This difference was most likely due to differential GAT-mediated uptake into brain cells of the former but not latter. In agreement, 3-aminopropyl(methyl)phosphinic acids were much more potent in producing hypothermia in rats even when administered i.c.v.

CONCLUSIONS AND IMPLICATIONS

An enhanced therapeutic window for 3-aminopropylphosphinic acids compared with 3-aminopropyl(methyl)phosphinic acids with respect to inhibition of TLOSR was observed and is probably mechanistically linked to neural cell uptake of the former but not latter group of compounds. These findings offer a platform for discovery of new GABA(B) receptor agonists for the treatment of reflux disease and other conditions where selective peripheral GABA(B) receptor agonism may afford therapeutic effects.

Increased risk of adverse pregnancy outcomes in women receiving zolpidem during pregnancy

This nationwide population-based study was carried out in Taiwan with the aim of comparing the risk of adverse pregnancy outcomes in women who received zolpidem treatment for insomnia during pregnancy with that in women who did not. The adverse outcomes identified and assessed were delivery of low-birth-weight (LBW) infants, preterm deliveries, delivery of small-for-gestational-age (SGA) infants, delivery of infants with congenital anomalies, and cesarean delivery. The incidences of these were compared between the groups after adjusting for other characteristics of the mothers and infants. The study used the Taiwan National Health Insurance Research Dataset (NHIRD) and birth-certificate registry. In total, the data from 2,497 mothers who received zolpidem treatment during pregnancy and those from 12,485 randomly selected mothers who did not receive the drug were included in the analysis. The results show that the adjusted odds ratios (ORs) for adverse pregnancy outcomes--LBW infants, preterm deliveries, SGA infants, and cesarean delivery--were all higher in mothers who received zolpidem treatment during pregnancy, relative to the randomly selected controls (1.39 (95% confidence interval (CI) = 1.17-1.64), 1.49 (95% CI = 1.28-1.74), 1.34 (95% CI = 1.20-1.49), and 1.74 (95% CI = 1.59-1.90), respectively). In conclusion, the risk of adverse pregnancy outcomes was higher in women who received zolpidem during pregnancy than in those who did not.

Intrathecal baclofen for autonomic instability due to spinal cord injury

Autonomic dysreflexia may occur following spinal cord injury above mid-thoracic level, commonly developing in the early posttraumatic period. Cardiovascular dysregulation is the most prominent feature, characterized by paroxysmal high blood pressure attacks, which are precipitated by distension of urinary bladder or bowels, skin wounds, or increased spastic muscle tone. Severe drops in blood pressure may occur in orthostatic conditions. Baclofen is effective for treating spasticity. While orally administered baclofen often fails to alleviate severe spasticity adequately, intrathecal baclofen (ITB) is more effective and thus is being used increasingly. A 61-year-old male sustained a cervical spinal cord injury, subsequently developing severe spastic tetraparesis, predominantly in the legs. Some 30 years later he experienced marked spasms of the muscles of the abdominal wall, leading to extreme fluctuations of blood pressure. After positive evaluation with ITB the patient underwent implantation of a pump-catheter-system for continuous ITB application. Abdominal wall spasms ceased entirely with a daily dose of 190 microg ITB, accompanied by a sustained normotensive blood pressure profile. However, spasms reoccurred after inadvertent reduction of ITB flow when increasing the pump's ITB concentration but subsided again when the optimal antispastic dose was reestablished. Baclofen per se has the potential of lowering blood pressure. In this patient, however, ITB treatment enabled permanent stabilization of insidious blood pressure fluctuations. It would appear that suppression of abdominal spasms prevented the triggering of dysautonomic crises. This case demonstrates that ITB administration may help to stabilize autonomic dysreflexia and orthostatic hypotension in patients with spinal cord lesions.

Central mechanisms II: pharmacology of brainstem pathways

Following systemic administration, centrally acting antitussive drugs are generally assumed to act in the brainstem to inhibit cough. However, recent work in humans has raised the possibility of suprapontine sites of action for cough suppressants. For drugs that may act in the brainstem, the specific locations, types of neurones affected, and receptor specificities of the compounds represent important issues regarding their cough-suppressant actions. Two medullary areas that have received the most attention regarding the actions of antitussive drugs are the nucleus of the tractus solitarius (NTS) and the caudal ventrolateral respiratory column. Studies that have implicated these two medullary areas have employed both microinjection and in vitro recording methods to control the location of action of the antitussive drugs. Other brainstem regions contain neurones that participate in the production of cough and could represent potential sites of action of antitussive drugs. These regions include the raphe nuclei, pontine nuclei, and rostral ventrolateral medulla. Specific receptor subtypes have been associated with the suppression of cough at central sites, including 5-HT1A, opioid (mu, kappa, and delta), GABA-B, tachykinin neurokinin-1 (NK-1) and neurokinin-2, non-opioid (NOP-1), cannabinoid, dopaminergic, and sigma receptors. Aside from tachykinin NK-1 receptors in the NTS, relatively little is known regarding the receptor specificity of putative antitussive drugs in particular brainstem regions. Our understanding of the mechanisms of action of antitussive drugs would be significantly advanced by further work in this area.

Functional organization of the central cough generation mechanism

Recent studies evaluating the effects of pulmonary afferents, chemoreceptors, and antitussive drugs on the cough motor pattern indicate that this reflex is regulated in a different manner than breathing. Furthermore, regulatory differences exist between tracheobronchial and laryngeal cough. We propose a functional model of the brainstem elements participating in the production of cough that accounts for these regulatory differences. The model incorporates known brainstem interneuronal pathways as well as novel regulatory elements for tracheobronchial and laryngeal cough. Each of these novel regulatory elements controls the excitability of a common motor pattern generation network. Given that cough and breathing are associated with profoundly different spatiotemporal alterations in motor drive to respiratory motoneurons, brainstem elements common to the generation of both behaviours must be capable of a high degree of plasticity.

Differential ontogeny of GABA(B)-receptor-mediated pre- and postsynaptic modulation of GABA and glycine transmission in respiratory rhythm-generating network in mouse

Rhythm generation in mature respiratory networks is influenced strongly by synaptic inhibition. In early neonates, GABA(A)-receptor- and glycine-receptor-mediated inhibition is not present, thus the question arises as to whether GABA(B)-receptor-mediated inhibition plays an important role. Using brainstem slices of neonatal mice (postnatal day, P0-P15), we analysed the role of GABA(B)-mediated modulation of GABA and glycine synaptic transmission in the respiratory network. Blockade of GABA uptake by nipecotic acid (0.25-2 mM) reduced the respiratory frequency. This reduction was prevented by the selective GABA(B) receptor antagonist CGP55845A (CGP) alone at P0-P3, but by bicuculline as well as CGP at P7-P15. Blockade of GABA(B) receptors by CGP increased the respiratory frequency at P0-P3, whereas it caused a reduction of frequency in older animals. The effect of CGP on respiratory frequency was diminished in the presence of bicuculline and strychnine in older but not in younger animals. The relative contribution of GABA(B)-receptor-mediated pre- and postsynaptic modulation was examined by analysing the effect of GABA(B) receptors on spontaneous and miniature IPSCs. In younger animals (P0-P3), the GABA(B) receptor agonist baclofen had no detectable effect on IPSC frequency, but caused a significant decrease in the amplitude. In older animals (P7-P15), baclofen decreased both the frequency and amplitude of spontaneous and miniature IPSCs. These results demonstrate that GABA(B)-receptor-mediated postsynaptic modulation plays an important role in the respiratory network from P0 on. GABA(B)-receptor-mediated presynaptic modulation develops with a longer postnatal latency, and becomes predominant within the first postnatal week.

GABA(B) receptors on vagal afferent pathways: peripheral and central inhibition

To investigate GABA(B) receptors along vagal afferent pathways, we recorded from vagal afferents, medullary neurons, and vagal efferents in ferrets. Baclofen (7-14 micromol/kg i.v.) reduced gastric tension receptor and nucleus tractus solitarii neuronal responses to gastric distension but not gastroduodenal mucosal receptor responses to cholecystokinin (CCK). GABA(B) antagonists CGP-35348 or CGP-62349 reversed effects of baclofen. Vagal efferents showed excitatory and inhibitory responses to distension and CCK. Baclofen (3 nmol i.c.v. or 7-14 micromol/kg i.v.) reduced both distension response types but reduced only inhibitory responses to CCK. CGP-35348 (100 nmol i.c.v. or 100 micromol/kg i.v.) reversed baclofen's effect on distension responses, but inhibitory responses to CCK remained attenuated. They were, however, reversed by CGP-62349 (0.4 nmol i.c.v.). In conclusion, GABA(B) receptors inhibit mechanosensitivity, not chemosensitivity, of vagal afferents peripherally. Mechanosensory input to brain stem neurons is also reduced centrally by GABA(B) receptors, but excitatory chemosensory input is unaffected. Inhibitory mechano- and chemosensory inputs to brain stem neurons (via inhibitory interneurons) are both reduced, but the pathway taken by chemosensory input involves GABA(B) receptors that are insensitive to CGP-35348.

Baclofen eliminates cluster lung breathing of the tadpole brainstem, in vitro

Intermittent lung ventilation is a respiratory pattern wherein breaths occur in clusters. Intermittent lung ventilation is common in amphibians and can occur in mammals. Isolated brainstems from postmetamorphic tadpoles exhibiting episodic lung ventilatory bursts were superfused with baclofen, a potent gamma-aminobutyric acid (GABA)(B) receptor agonist. At moderate concentrations (0.125 to 0.5 microM), the number of lung bursts per episode decreased but their overall frequency was unchanged. At 0.5 microM, only 1.22+/-0.24 lung bursts occurred per episode, indicating virtually no clustering. Only at higher concentrations was overall breathing frequency decreased. Therefore, at moderate concentrations of baclofen continuous ventilation replaced episodic ventilation, suggesting that a GABA(B) receptor-dependent pathway may regulate the clustering of lung breaths.

Postnatal development of GABAB receptor-mediated modulation of voltage-activated Ca2+ currents in mouse brain-stem neurons

GABAB receptors modulate respiratory rhythm generation in adult mammals. However, little is currently known of their functional significance during postnatal development. In the present investigation, the effects of GABAB receptor activation on voltage-activated Ca2+ currents were examined in rhythmically active neurons of the pre-Bötzinger complex (PBC). Both low- (LVA) and high-voltage-activated (HVA) Ca2+ currents were present from the first postnatal day (P1). The density of LVA Ca2+ currents increased during the first week, whilst the density of HVA Ca2+ currents increased after the first week. In the second postnatal week, the HVA Ca2+ currents were composed of L- (47 +/- 10%) and N-type (21 +/- 8%) currents plus a 'residual' current, whilst there were no N-type currents detectable in the first few days. The GABAB receptor agonist baclofen (30 microM) increased LVA Ca2+ currents (30 +/- 11%) at P1-P3, but it decreased the currents (35 +/- 11%) at P7-P15 without changing its time course. At all ages, baclofen (30 microM) decreased the HVA Ca2+ currents by approximately 54%. Threshold of baclofen effects on both LVA and HVA Ca2+ currents was 5 microM at P1-P3 and lower than 1 microM at P7-P15. The effect of baclofen was abolished in the presence of the GABAB receptor antagonist CGP 55845A (50 nM). We conclude that both LVA and HVA Ca2+ currents increased postnatally. The GABAB receptor-mediated modulation of these currents undergo marked developmental changes during the first two postnatal weeks, which may contribute essentially to modulation of respiratory rhythm generation.

Influence of central antitussive drugs on the cough motor pattern

The present study was conducted to determine the effects of administration of centrally active antitussive drugs on the cough motor pattern. Electromyograms of diaphragm and rectus abdominis muscles were recorded in anesthetized, spontaneously breathing cats. Cough was produced by mechanical stimulation of the intrathoracic trachea. Centrally acting drugs administered included codeine, morphine, dextromethorphan, baclofen, CP-99,994, and SR-48,968. Intravertebral artery administration of all drugs reduced cough number (number of coughs per stimulus trial) and rectus abdominis burst amplitude in a dose-dependent manner. Codeine, dextromethorphan, CP-99,994, SR-48,968, and baclofen had no effect on cough cycle timing (CTtot) or diaphragm amplitude during cough, even at doses that inhibited cough number by 80-90%. Morphine lengthened CTtot and inhibited diaphragm amplitude during cough, but these effects were not dose dependent. Only CP-99,994 altered the eupneic respiratory pattern. Central antitussive drugs primarily suppress cough by inhibition of expiratory motor drive and cough number. CTtot and inspiratory motor drive are relatively insensitive to the effects of these drugs. CTtot can be controlled independently from cough number.