Effects of the designer drug 4-methylamphetamine on core temperature and serotonin levels in the striatum and hippocampus of rats.

New psychoactive substances (NPS) are typically synthesized in clandestine laboratories in an attempt to chemically modify already federally regulated drugs in an effort to circumvent the law. Drugs derived from a phenethylamine pharmacophore, such as 4-chloroamphetamine and 3,4-methylenedioxymethamphetamine (MDMA), reliably induce thermogenesis and serotonergic deficits in the striatum and hippocampus of rodents. 4-methylamphetamine (4-MA), a relative newcomer to the NPS scene, was originally investigated in the mid-1900 s as a potential anorexigenic agent. With its phenethylamine pharmacophore, 4-MA was hypothesized to produce similar toxicological alterations as its chemical analogs. In the present study, three doses (1.0, 2.5, and 5.0 mg/kg, ip.) of 4-MA were administered to rats twice daily for two days. Core temperature data were calculated and analyzed as temperature area under the curve (TAUC). On the second day of dosing, a hypothermic response to 4-MA (2.5 and 5.0 mg/kg) was noted between 0.5 and 2.0 h post-treatment. Only the highest dose of 4-MA decreased body weight on the second day of treatment and maintained this reduction in weight for seven days after treatment ceased. None of the doses of 4-MA evaluated significantly altered serotonin levels in the hippocampus or striatum seven days after final treatment. The present findings demonstrate that the 4-methyl substitution to amphetamine generates a pharmacological and toxicological profile that differs from other similar phenethylamine analogs.

Altered States and Social Bonds: Effects of MDMA and Serotonergic Psychedelics on Social Behavior as a Mechanism Underlying Substance-Assisted Therapy.

There has been renewed interest in the use of 3,4-methylenedioxy-methamphetamine (MDMA) and serotonergic psychedelics in the treatment of multiple psychiatric disorders. Many of these compounds are known to produce prosocial effects, but how these effects relate to therapeutic efficacy and the extent to which prosocial effects are unique to a particular drug class is unknown. In this article, we present a narrative overview and compare evidence for the prosocial effects of MDMA and serotonergic psychedelics to elucidate shared mechanisms that may underlie the therapeutic process. We discuss 4 categories of prosocial effects: altered self-image, responses to social reward, responses to negative social input, and social neuroplasticity. While both categories of drugs alter self-perception, MDMA may do so in a way that is less related to the experience of mystical-type states than serotonergic psychedelics. In the case of social reward, evidence supports the ability of MDMA to enhance responses and suggests that serotonergic psychedelics may also do so, but more research is needed in this area. Both drug classes consistently dampen reactivity to negative social stimuli. Finally, preclinical evidence supports the ability of both drug classes to induce social neuroplasticity, promoting adaptive rewiring of neural circuits, which may be helpful in trauma processing. While both MDMA and serotonergic psychedelics produce prosocial effects, they differ in the mechanisms through which they do this. These differences affect the types of psychosocial interventions that may work best with each compound.

Innate cocaine-seeking vulnerability arising from loss of serotonin-mediated aversive effects of cocaine in rats.

Cocaine blocks dopamine reuptake, thereby producing rewarding effects that are widely studied. However, cocaine also blocks serotonin uptake, which we show drives, in rats, individually variable aversive effects that depend on serotonin 2C receptors (5-HT2CRs) in the rostromedial tegmental nucleus (RMTg), a major GABAergic afferent to midbrain dopamine neurons. 5-HT2CRs produce depolarizing effects in RMTg neurons that are particularly strong in some rats, leading to aversive effects that reduce acquisition of and relapse to cocaine seeking. In contrast, 5-HT2CR signaling is largely lost after cocaine exposure in other rats, leading to reduced aversive effects and increased cocaine seeking. These results suggest a serotonergic biological marker of cocaine-seeking vulnerability that can be targeted to modulate drug seeking.

The role of extracellular serotonin and MDMA in the sensitizing effects of MDMA.

MDMA is a non-selective monoamine releasing stimulant with potent serotonergic effects - a pharmacological effect not typically associated with drugs of misuse or efficacious reinforcers. Nonetheless, MDMA is misused by humans and self-administered by laboratory animals. We have previously shown that repeated exposure to MDMA sensitized both the locomotor activating and reinforcing effects of MDMA in rats. Because repeated MDMA exposure often results in decreased markers of serotonin neurotransmission, it is possible that this might underlie the sensitizing effects of MDMA. This was examined in the current study. Male Sprague-Dawley rats were stereotaxically implanted with guide cannula in the medial striatum. They were then pre-treated with saline (n =  11) or MDMA (10 mg/kg, i.p.; n =  10), once daily for five days. Two-days later, all rats received ascending doses of MDMA (0.0, 5.0, 10.0, mg/kg, i.p.) administered at 2 hr intervals, during which locomotor activity was measured and microdialysis samples were collected. Microdialysates were analyzed using liquid chromatography-mass spectrometry and the concentrations of serotonin and MDMA were quantified. Acute MDMA administration produced dose-dependent increases in locomotor activity, which was significantly enhanced by MDMA pre-treatment. Acute MDMA also produced dose-dependent increases in medial-striatal serotonin and MDMA, but this was not impacted by MDMA pre-treatment. These results suggest that the sensitizing effects of MDMA are not due to changes in MDMA-produced synaptic overflow of serotonin in the medial striatum or the absorption/elimination of systemically administered MDMA. More likely candidates are alterations in serotonin receptor mechanisms and/or dopamine neurotransmission following repeated exposure.

Serotonergic psychedelic drugs LSD and psilocybin reduce the hierarchical differentiation of unimodal and transmodal cortex.

Lysergic acid diethylamide (LSD) and psilocybin are serotonergic psychedelic compounds with potential in the treatment of mental health disorders. Past neuroimaging investigations have revealed that both compounds can elicit significant changes to whole-brain functional organization and dynamics. A recent proposal linked past findings into a unified model and hypothesized reduced whole-brain hierarchical organization as a key mechanism underlying the psychedelic state, but this has yet to be directly tested. We applied a non-linear dimensionality reduction technique previously used to map hierarchical connectivity gradients to assess cortical organization in the LSD and psilocybin state from two previously published pharmacological resting-state fMRI datasets (N = 15 and 9, respectively). Results supported our primary hypothesis: The principal gradient of cortical connectivity, describing a hierarchy from unimodal to transmodal cortex, was significantly flattened under both drugs relative to their respective placebo conditions. Between-condition contrasts revealed that this was driven by a reduction of functional differentiation at both hierarchical extremes - default and frontoparietal networks at the upper end, and somatomotor at the lower. Gradient-based connectivity mapping indicated that this was underpinned by a disruption of modular unimodal connectivity and increased unimodal-transmodal crosstalk. Results involving the second and third gradient, which, respectively represent axes of sensory and executive differentiation, also showed significant alterations across both drugs. These findings provide support for a recent mechanistic model of the psychedelic state relevant to therapeutic applications of psychedelics. More fundamentally, we provide the first evidence that macroscale connectivity gradients are sensitive to an acute pharmacological manipulation, supporting a role for psychedelics as scientific tools to perturb cortical functional organization.

Modulating role of serotonergic signaling in sleep and memory.

Serotonin is an important neurotransmitter with various receptors and wide-range effects on physiological processes and cognitive functions including sleep, learning, and memory. In this review study, we aimed to discuss the role of serotonergic receptors in modulating sleep-wake cycle, and learning and memory function. Furthermore, we mentioned to sleep deprivation, its effects on memory function, and the potential interaction with serotonin. Although there are thousands of research articles focusing on the relationship between sleep and serotonin; however, the pattern of serotonergic function in sleep deprivation is inconsistent and it seems that serotonin has not a certain role in the effects of sleep deprivation on memory function. Also, we found that the injection type of serotonergic agents (systemic or local), the doses of these drugs (dose-dependent effects), and up- or down-regulation of serotonergic receptors during training with various memory tasks are important issues that can be involved in the effects of serotonergic signaling on sleep-wake cycle, memory function, and sleep deprivation-induced memory impairments. This comprehensive review was conducted in the PubMed, Scopus, and ScienceDirect databases in June and July 2021, by searching keywords sleep, sleep deprivation, memory, and serotonin.

Antidepressant and anxiolytic compounds isolated from Salvia elegans interact with serotonergic drugs.

Salvia elegans belongs to a genus plants with biological activities in central nervous system. In this work, the purpose was to evaluate the anxiolytic and antidepressant effects of fractions and compounds isolated from S. elegans and its interaction with serotoninergic drugs by using behavioral tests in mice. Fractions from aerial parts of S. elegans were obtained by column chromatography, SeF1, SeF2, SeF3, and SeF4. Each of them was administered to 25 mg/k in ICR mice subject to forced swimming test (FST), or elevated plus maze test (EPM), or open field test (OFT). The most active fractions were chemically separated until compounds, which were analyzed as anxiolytic or antidepressant and the coadministration of these treatments with 5-HT1A and 5-HT2 drugs was measured in the different biological tests. All fractions were anxiolytic and antidepressant, oleanolic acid (OA) was found in SeF2, and from SeF3, a mixture of terpenes was found; a GC-MS analysis confirmed the presence of two main compounds: rosifoliol and agaraspirol (TM, mixture of terpenes). TM (doses-response curve, 0.01, 0.1, 0.5, 1.0, and 2.0 mg/kg) and OA (5 mg/kg) were also evaluated demonstrating an antidepressant and anxiolytic effect, respectively. The combination of TM (0.5 mg/kg) with 8-OH (selective 5-HT1A receptor agonist) induced an increment of antidepressant activity, while with the antagonist WAY-100635, the effect diminished. But with DOI (5-HT1c/5-HT2 receptor agonist), there was no change, and with KET (5-HT2 receptor antagonist), the activity was increased. When OA is co-administered with 8-OH or with DOI, the anxiolytic activity of this terpene, diminished; but with the combination with antagonists, the effect of OA shows no change. TM and OA were antidepressant and anxiolytic, respectively, on mice exposed to different tests, and these are able to interact with serotoninergic drugs.

Two randomized, double-blind, placebo-controlled trials and one open-label, long-term trial of brexpiprazole for the acute treatment of bipolar mania.

BACKGROUND: Brexpiprazole is a dopamine/serotonin receptor partial agonist (D2, 5-HT1A) and antagonist (5-HT2A) approved for treatment of schizophrenia and major depressive disorder (adjunct to antidepressants). AIMS: This study aimed to investigate brexpiprazole as monotherapy in acute mania (bipolar I disorder) in two short-term (ST) studies (study 080 and study 081) and one open-label (OL) extension (study 083). METHODS: ST studies were three-week randomized, double-blind, flexible dose (2-4 mg/day), placebo-controlled studies. The primary endpoint was mean change in Young Mania Rating Scale (YMRS) total score from baseline to day 21. The OL study was a 26-week flexible dose (2-4 mg/day) study for patients completing the ST studies. RESULTS: A total of 164 and 158 (study 080) and 170 and 162 (study 081) inpatients with DSM-5 mania with/without mixed features were randomized to placebo or brexpiprazole, respectively. The primary analyses did not show a statistically significant difference between brexpiprazole and placebo: study 080: least squares mean difference (95% confidence limits): 0.14 (-1.74, 2.03), p = 0.8797; study 081: -1.62 (-3.56, 0.32), p = 0.1011. OL study patients (n = 381) demonstrated a gradual improvement in YMRS total score. Akathisia was the only adverse event, with an incidence of ⩾5% with brexpiprazole and more than placebo in the ST studies, or ⩾5% in the OL study. Brexpiprazole was more efficacious in patients with impaired or no insight (predominantly EU patients) than in patients with excellent insight (predominantly US patients). CONCLUSIONS: Further studies are necessary to address the potential efficacy of brexpiprazole in acute mania, which should ensure that the study sample is severe enough (especially with regard to insight), and that the dose/titration schedule is not too modest.

Methylenedioxymethamphetamine (MDMA): Serotonergic and dopaminergic mechanisms related to its use and misuse.

Methylenedioxymethamphetamine (MDMA) is an amphetamine analogue that preferentially stimulates the release of serotonin (5HT) and results in relatively small increases in synaptic dopamine (DA). The ratio of drug-stimulated increases in synaptic DA, relative to 5HT, predicts the abuse liability; drugs with higher DA:5HT ratios are more likely to be abused. Nonetheless, MDMA is a drug that is misused. Clinical and preclinical studies have suggested that repeated MDMA exposure produces neuroadaptive responses in both 5HT and DA neurotransmission that might explain the development and maintenance of MDMA self-administration in some laboratory animals and the development of a substance use disorder in some humans. In this paper, we describe the research that has demonstrated an inhibitory effect of 5HT on the acquisition of MDMA self-administration and the critical role of DA in the maintenance of MDMA self-administration in laboratory animals. We then describe the circuitry and 5HT receptors that are positioned to modulate DA activity and review the limited research on the effects of MDMA exposure on these receptor mechanisms.

Ketamine and Serotonergic Psychedelics: Common Mechanisms Underlying the Effects of Rapid-Acting Antidepressants.

BACKGROUND: The glutamatergic modulator ketamine has created a blueprint for studying novel pharmaceuticals in the field. Recent studies suggest that "classic" serotonergic psychedelics (SPs) may also have antidepressant efficacy. Both ketamine and SPs appear to produce rapid, sustained antidepressant effects after a transient psychoactive period. METHODS: This review summarizes areas of overlap between SP and ketamine research and considers the possibility of a common, downstream mechanism of action. The therapeutic relevance of the psychoactive state, overlapping cellular and molecular effects, and overlapping electrophysiological and neuroimaging observations are all reviewed. RESULTS: Taken together, the evidence suggests a potentially shared mechanism wherein both ketamine and SPs may engender rapid neuroplastic effects in a glutamatergic activity-dependent manner. It is postulated that, though distinct, both ketamine and SPs appear to produce acute alterations in cortical network activity that may initially produce psychoactive effects and later produce milder, sustained changes in network efficiency associated with therapeutic response. However, despite some commonalities between the psychoactive component of these pharmacologically distinct therapies-such as engagement of the downstream glutamatergic pathway-the connection between psychoactive impact and antidepressant efficacy remains unclear and requires more rigorous research. CONCLUSIONS: Rapid-acting antidepressants currently under investigation may share some downstream pharmacological effects, suggesting that their antidepressant effects may come about via related mechanisms. Given the prototypic nature of ketamine research and recent progress in this area, this platform could be used to investigate entirely new classes of antidepressants with rapid and robust actions.

The Pharmacological Case for Cannabigerol.

Medical cannabis and individual cannabinoids, such as Δ9-tetrahydrocannabinol (Δ9-THC) and cannabidiol (CBD), are receiving growing attention in both the media and the scientific literature. The Cannabis plant, however, produces over 100 different cannabinoids, and cannabigerol (CBG) serves as the precursor molecule for the most abundant phytocannabinoids. CBG exhibits affinity and activity characteristics between Δ9-THC and CBD at the cannabinoid receptors but appears to be unique in its interactions with α-2 adrenoceptors and 5-hydroxytryptamine (5-HT1A). Studies indicate that CBG may have therapeutic potential in treating neurologic disorders (e.g., Huntington disease, Parkinson disease, and multiple sclerosis) and inflammatory bowel disease, as well as having antibacterial activity. There is growing interest in the commercial use of this unregulated phytocannabinoid. This review focuses on the unique pharmacology of CBG, our current knowledge of its possible therapeutic utility, and its potential toxicological hazards. SIGNIFICANCE STATEMENT: Cannabigerol is currently being marketed as a dietary supplement and, as with cannabidiol (CBD) before, many claims are being made about its benefits. Unlike CBD, however, little research has been performed on this unregulated molecule, and much of what is known warrants further investigation to identify potential areas of therapeutic uses and hazards.

Serotonin research: Crossing scales and boundaries.

Nearly 100 years after the discovery of serotonin, its role remains elusive. Modulation of serotonin transmission is considered in numerous central nervous system (CNS) diseases including depression, anxiety, schizophrenia, obsessive-compulsive disorders, addiction, Parkinson's disease, and Alzheimer's disease. The therapeutic strategies based on serotonin systems have evolved thanks to better identification of the involvement of serotonin in various diseases, the better use of animal models, a better understanding of the molecular environment of serotonin receptors, and ultimately the better understanding of the interaction of serotonin neurotransmission with other biological systems. Some 5-HT receptors are still the object of numerous investigations including 5-HT1A, 5-HT2A, and 5-HT6 receptor subtypes. It is noteworthy that the direction of research is moving towards a simultaneous action at multiple targets either through different 5-HT targets or the consideration of both 5-HT and other targets to achieve better therapeutic responses.

Isoquinolinone derivatives as potent CNS multi-receptor D2/5-HT1A/5-HT2A/5-HT6/5-HT7 agents: Synthesis and pharmacological evaluation.

In this study, a series of novel Isoquinolinone derivatives were synthesized as potential multi-target antipsychotics. Among these, compound 13 showed high affinity for dopamine D2 and serotonin 5-HT1A, 5-HT2A, 5-HT6, and 5-HT7 receptors, showed low affinity for off-target receptors (5-HT2C, H1, and α1), and negligible effects on ether-a-gogo-related gene (hERG; i.e., reduced QT interval prolongation). An animal behavioral study revealed that compound 13 reversed APO-induced hyperlocomotion, MK-801-induced hyperactivity, and DOI-induced head twitch. Moreover, compound 13 exhibited a high threshold for acute toxicity, a lack of tendency to induce catalepsy, and did not cause prolactin secretion or weight gain when compared to risperidone. Furthermore, in the forced swim test, tail suspension test, and novel object recognition test, treatment with compound 13 resulted in improvements in depression and cognitive impairment. In addition, compound 13 had a favorable pharmacokinetic profile in rats. Thus, the antipsychotic drug-like effects of compound 13 indicate that it may be useful for developing a novel class of drugs for the treatment of schizophrenia.

Loss of diffuse noxious inhibitory control after traumatic brain injury in rats: A chronic issue.

Chronic pain is one of the most challenging and debilitating symptoms to manage after traumatic brain injury (TBI), yet the underlying mechanisms remain elusive. The disruption of normal endogenous pain control mechanisms has been linked to several forms of chronic pain and may play a role in pain after TBI. We hypothesized therefore that dysfunctional descending noradrenergic and serotonergic pain control circuits may contribute to the loss of diffuse noxious inhibitory control (DNIC), a critical endogenous pain control mechanism, weeks to months after TBI. For these studies, the rat lateral fluid percussion model of mild TBI was used along with a DNIC paradigm involving a capsaicin-conditioning stimulus. We observed sustained failure of the DNIC response up to 180-days post injury. We confirmed, that descending α2 adrenoceptor-mediated noradrenergic signaling was critical for endogenous pain inhibition in uninjured rats. However, augmenting descending noradrenergic signaling using reboxetine, a selective noradrenaline reuptake inhibitor, failed to restore DNIC after TBI. Furthermore, blocking serotonin-mediated descending signaling using selective spinal serotonergic fiber depletion with 5, 7-dihydroxytryptamine was also unsuccessful at restoring endogenous pain modulation after TBI. Unexpectedly, increasing descending serotonergic signaling using the selective serotonin reuptake inhibitor escitalopram and the serotonin-norepinephrine reuptake inhibitor duloxetine restored the DNIC response in TBI rats at both 49- and 180- days post injury. Consistent with these observations, spinal serotonergic fiber depletion with 5, 7-dihydroxytryptamine eliminated the effects of escitalopram. Intact α2 adrenoceptor signaling, however, was not required for the serotonin-mediated restoration of DNIC after TBI. These results suggest that TBI causes maladaptation of descending nociceptive signaling mechanisms and changes in the function of both adrenergic and serotonergic circuits. Such changes could predispose those with TBI to chronic pain.

Modulation of the Paracrine Kynurenic System in Bone as a New Regulator of Osteoblastogenesis and Bone Mineral Status in an Animal Model of Chronic Kidney Disease Treated with LP533401.

An increase in the peripheral synthesis of serotonin and kynurenine, observed during the chronic kidney disease (CKD) course, is negatively associated with bone health. Serotonin and kynurenine are connected by the common precursor, tryptophan. LP533401 is an inhibitor of peripheral serotonin synthesis. This study aimed to establish if the inhibition of serotonin synthesis by LP533401 may affect the kynurenine pathway activity in bone tissue and its potential consequence with regard to osteogenesis and bone mineral status. Nephrectomized rats were treated with LP533401 at a dose of 30 and 100 mg/kg daily for eight weeks. Tryptophan and kynurenine concentrations were determined, and tryptophan 2,3-dioxygenase (TDO) expression was assessed. We discovered the presence of a TDO-dependent, paracrine kynurenic system in the bone of rats with CKD. Its modulation during LP533401 treatment was associated with impaired bone mineral status. Changes in TDO expression affecting the kynurenine pathway activity were related to the imbalance between peripheral serotonin and 25-hydroxyvitamin D. There were also close associations between the expression of genes participating in osteoblastogenesis and activation of the kynurenine pathway in the bones of LP53301-treated rats. Our results represent the next step in studying the role of tryptophan metabolites in renal osteodystrophy.

Genetic deletion of Rgs12 in mice affects serotonin transporter expression and function in vivo and ex vivo.

BACKGROUND: Regulator of G protein Signaling (RGS) proteins inhibit G protein-coupled receptor (GPCR) signaling, including the signals that arise from neurotransmitter release. We have shown that RGS12 loss diminishes locomotor responses of C57BL/6J mice to dopamine transporter (DAT)-targeting psychostimulants. This diminution resulted from a brain region-specific upregulation of DAT expression and function in RGS12-null mice. This effect on DAT prompted us to investigate whether the serotonin transporter (SERT) exhibits similar alterations upon RGS12 loss in C57BL/6J mice. AIMS: Does RGS12 loss affect (a) hyperlocomotion to the preferentially SERT-targeting psychostimulant 3,4-methylenedioxymethamphetamine (MDMA), (b) SERT expression and function in relevant brain regions, and/or (c) serotonergically modulated behaviors? METHODS: Open-field and spontaneous home-cage locomotor activities were quantified. 5-HT, 5-HIAA, and SERT levels in brain-region homogenates, as well as SERT expression and function in brain-region tissue preparations, were measured using appropriate biochemical assays. Serotonergically modulated behaviors were assessed using forced swim and tail suspension paradigms, elevated plus and elevated zero maze tests, and social interaction assays. RESULTS: RGS12-null mice displayed no hyperlocomotion to 10 mg/kg MDMA. There were brain region-specific alterations in SERT expression and function associated with RGS12 loss. Drug-naïve RGS12-null mice displayed increases in both anxiety-like and anti-depressive-like behaviors. CONCLUSION: RGS12 is a critical modulator of serotonergic neurotransmission and serotonergically modulated behavior in mice; lack of hyperlocomotion to low dose MDMA in RGS12-null mice is related to an alteration of steady-state SERT expression and 5-HT uptake.

Use of the French healthcare insurance database to estimate the prevalence of exposure to potential drug-drug interactions.

PURPOSE: Drug-drug interactions (DDIs) require monitoring in an aging population with increasing polypharmacy exposure. We aimed to estimate the prevalence of exposure to potential DDIs using the French healthcare insurance system database, for six DDIs with various clinical relevance: angiotensin II receptor blockers or angiotensin-converting enzyme inhibitors and nonsteroidal anti-inflammatory drugs (ARBs-ACEIs + NSAIDs), antiplatelet agents and NSAIDs (AAP + NSAIDs), serotonergic drugs and tramadol (SD + T), statins and macrolides (S + M), oral anticoagulant and NSAIDs (OAC + NSAIDs), and colchicine and macrolides (C + M). METHODS: We used exhaustive healthcare data from a 1/97th random sample of the population covered by the French health insurance system (EGB) between 2006 and 2016. Exposure to a DDI was defined as overlapping exposure to two interacting drugs. The prevalence of exposure was estimated by year. RESULTS: Prevalence of exposure in 2016 was estimated at 3.7% for ARBs-ACEIs + NSAIDs, 1.5% for AAP + NSAIDs, 0.76% for SD + T, 0.36% for S + M, 0.24% for AOC + NSAIDs, and 0.02% for C + M. In 26% to 58% of episodes of exposure, the two interacting drugs were prescribed by the same physician and dispensed by the same pharmacy the same day. Between 2006 and 2016, the yearly prevalence was increasing for SD + T and for DDIs involving NSAIDs, and it was decreasing for those involving macrolides. CONCLUSION: Exposures to potential DDIs in France are not uncommon with a high proportion resulting from a co-prescription by the same physician. Monitoring the prevalence of exposure to DDIs is needed to implement prevention measures. Administrative data enable this surveillance in large and representative cohorts.

Comparative therapeutic index, lethal time and safety margin of various toxicants and snake antivenoms using newly derived and old formulas.

OBJECTIVE: The assessment of clinical efficacy and toxicity is very important in pharmacology and toxicology. The effects of psychostimulants (e.g. amphetamine), psychotomimetics (e.g. Cannabis sativus) and snake antivenoms are sometimes unpredictable even at lower doses, leading to serious intoxication and fatal consequences. Hence, there is need to re-assess some formulas for calculation of therapeutic index, lethal time and safety margin with a view to identifying therapeutic agents with remarkable toxicity potentials. RESULTS: The therapeutic index formula [Formula: see text] was derived from T1 = LD50/ED50 and ED50 = [Formula: see text]. Findings have shown that, therapeutic index is a function of death reversal (s), safety factor (10-4) and weight of animal (Wa). However, the new safety margin formula [Formula: see text] derived from LT50 = [Formula: see text] and MS = [Formula: see text] shows that safety margin is a function of cube root of ratio between LT50 and LD50 and ED100th. Concentration (k) of toxicant at the receptor [Formula: see text] derived from D1 × Tn = K and LD1 = [Formula: see text] shows that therapeutic index, lethal time and safety margin is a function of drug or toxicant concentration at the receptor, the drug-receptor interaction and dose of toxicant or drug administered at a particular time.