Brimonidine.

Brimonidine is a highly selective 2-adrenoceptor agonist that lowers intraocular pressure (IOP) by decreasing aqueous humor production and increasing aqueous humor outflow via the uveoscleral route. Brimonidine is used to treat glaucoma and other eye conditions. Brimonidine is a topical medication that is used mainly to treat open-angle glaucoma and ocular hypertension in the eyelids. The purpose of this chapter is to provide a comprehensive discussion of Brimonidine's nomenclature, physiochemical properties, preparation methods, identification procedures, and numerous qualitative and quantitative analytical techniques, as well as its ADME profiles and pharmacological effects. In addition, the chapter contains numerous approaches for separating brimonidine from other medications in combination formulations utilizing chromatographic techniques and other spectroscopic approaches.

Pineal Gland Culture.

Pineal gland secretes the hormone melatonin at night with a circadian rhythm. The synthesis and secretion of melatonin are stimulated at night by norepinephrine released by sympathetic postganglionic neurons projecting from the superior cervical ganglia. Norepinephrine simultaneously activates α- and ß-adrenoceptors, triggering melatonin synthesis.To study the regulation of melatonin production and secretion, it is very convenient to use an ex vivo preparation. Thus, it is possible to keep intact pineal glands in culture and to study the actions of agonists, antagonists, modulators, toxic agents, etc., in melatonin synthesis. Artificial melatonin synthesis stimulation in vitro is usually achieved by using a ß-adrenergic agonist alone or in association with an α-adrenergic agonist. In this chapter, the methodology of cultured pineal glands will be described. Several papers were published by our group using this methodology, approaching the role played in melatonin synthesis control by angiotensin II and IV, insulin, glutamate, voltage-gated calcium channels, anhydroecgonine methyl ester (AEME, crack-cocaine product), monosodium glutamate (MSG), signaling pathways like NFkB, pathophysiological conditions like diabetes, etc.

Brimonidine tartrate ophthalmic solution 0.025% for redness relief: an overview of safety and efficacy.

INTRODUCTION: Ocular redness, or conjunctival hyperemia, is a common ophthalmic sign associated with reduced quality of life. For redness without apparent underlying pathology, topical ophthalmic decongestants have been widely used. AREAS COVERED: Brimonidine tartrate was approved in 2017 as a topical vasoconstrictor at a 0.025% concentration for relief of ocular redness. Since then, investigators have reported on efficacy and safety findings from studies evaluating low-dose brimonidine for reducing ocular redness. EXPERT OPINION: Brimonidine is highly selective for α2-adrenergic receptors. Clinical trials have so far shown that the drug in low doses significantly reduces ocular redness in comparison to vehicle for up to 8 hours. Brimonidine-treated eyes did not present side effects of other vasoconstrictors, such as hypotension, cardiac arrhythmia, or drowsiness. Ocular adverse events, such as allergic reactions and redness rebound, were also minimal. In this review, we examine in detail published literature on the mechanism of brimonidine tartrate and its efficacy and safety in relieving conjunctival hyperemia.

The Pharmacological Effects of Phenylephrine are Indirect, Mediated by Noradrenaline Release from the Cytoplasm.

Phenylephrine (PE) is a canonical α1-adrenoceptor-selective agonist. However, unexpected effects of PE have been observed in preclinical and clinical studies, that cannot be easily explained by its actions on α1-adrenoceptors. The probability of the involvement of α2- and ß-adrenoceptors in the effect of PE has been raised. In addition, our earlier study observed that PE released noradrenaline (NA) in a [Ca2+]o-independent manner. To elucidate this issue, we have investigated the effects of PE on [3H]NA release and α1-mediated smooth muscle contractions in the mouse vas deferens (MVD) as ex vivo preparation. The release experiments were designed to assess the effects of PE at the presynaptic terminal, whereas smooth muscle isometric contractions in response to electrical field stimulation were used to measure PE effect postsynaptically. Our results show that PE at concentrations between 0.3 and 30 µM significantly enhanced the resting release of [3H]NA in a [Ca2+]o-independent manner. In addition, prazosin did not affect the release of NA evoked by PE. On the contrary, PE-evoked smooth muscle contractions were inhibited by prazosin administration indicating the α1-adrenoceptor-mediated effect. When the function of the NA transporter (NAT) was attenuated with nisoxetine, PE failed to release NA and the contractions were reduced by approximately 88%. The remaining part proved to be prazosin-sensitive. The present work supports the substantial indirect effect of PE which relays on the cytoplasmic release of NA, which might explain the reported side effects for PE.

Systemic toxicity from subcutaneous brimonidine injection successfully treated with naloxone.

Brimonidine is a topical ophthalmic alpha-2 adrenergic agonist solution used to treat glaucoma. The toxidrome includes drowsiness, lethargy, hypotension, bradycardia, and respiratory depression when ingested in infants. We report a case of intentional subcutaneous injection of brimonidine in an elderly patient resulting in hypotension and CNS depression that responded to naloxone. A 73-year-old female with a past medical history significant for glaucoma, hypertension, and indwelling pacemaker presented to the emergency department after injecting her brimonidine tartrate ophthalmic solution subcutaneously (SQ). The patient was not taking any antihypertensive medications or opioids. Initial presentation consisted of lethargy, a paced rhythm of 60 bpm, and blood pressure of 91/24 mmHg with a MAP of 46. Due to central nervous system depression, 3 mg of intranasal naloxone was administered. The patient was treated with intravenous fluids and escalating doses of naloxone and required a continuous infusion. Mental status and vital signs subsequently improved. The patient was admitted to the ICU and naloxone was subsequently weaned over 12 h. Systemic central alpha-2 adrenergic agonist toxicity resulted from SQ brimonidine injection. Central alpha-2 adrenergic agonist overdoses present as sympatholytic effects including CNS depression, bradycardia, hypotension, and may mimic the opioid toxidrome. Brimonidine SQ injection has not previously been reported and this case has similar findings to other central alpha-2 adrenergic agonist poisonings. Naloxone has previously shown variable reversal of CNS depression in central alpha-2 overdose. In this case, high-dose naloxone was useful for reversing CNS depression and hemodynamic instability.

The benefit of scratch patch testing to demonstrate ocular contact allergy to brimonidine tartrate.

INTRODUCTION: Ocular allergies to brimonidine are frequent in patients treated for glaucoma. There is variability in reporting due to the lack of diagnostic criteria and the absence of cutaneous testing. Many false-negative patch tests (PT) have been described. Alternative methods, such as strip and scratch PT, have been used without a standardized method. OBJECTIVES: The primary objective is to identify the best method of cutaneous testing and brimonidine concentration for patch testing. The secondary objective is to identify clinical signs and symptoms suggestive of ocular allergy. PATIENTS AND METHODS: A retrospective review of patient files suspected of brimonidine ocular allergy was performed. Patch testing method, brimonidine concentration and clinical symptoms were reviewed. RESULTS: Of the 36 patients identified, half tested positive for brimonidine for at least one of the testing methods. The scratch PT demonstrated 17 positive reactions (94% detection rate). Three patients reacted with strip PT. No positive results were found with standard PT. The 5% brimonidine concentration demonstrated the highest sensitivity. The absence of eyelid pruritus was associated with negative testing. CONCLUSION: In the investigation of ocular allergy to brimonidine, scratch PT proved to be an essential tool. Brimonidine 5% pet. appeared as the most sensitive concentration for scratch PT.

Effect of Topically Applied 0.5% Apraclonidine Versus 0.5% Timolol Maleate on Intraocular Pressure of Healthy Horses.

This study aims to assess the effect of topical 0.5% apraclonidine on Intraocular pressure (IOP) in horses and compare the effects of timolol maleate 0.5% with 0.5% apraclonidine in the equine eye. Twenty healthy female thoroughbred horses were used. Horses were divided into two groups. Ten horses received single dose of 0.2 mL of 0.5% apraclonidine in one randomly selected eye and the contralateral eye received single dose of 0.2 mL of artificial tears. In the second group, 10 horses received single dose of 0.2 mL of 0.5% timolol maleate in one eye and the opposite eye received single dose of placebo (0.2 mL of artificial tears). Intraocular pressure was measured using rebound tonometer at the baseline and 30, 60, 120, 240, 360 minutes, and 24 hours after topical ophthalmic drops instillation. Any ocular side effects were recorded at each time point. Mean (SD) baseline IOPs of the treated and placebo eyes were 26.2(3.1) and 23.5(3.4) in apraclonidine group, and 25.7(2.6) and 23.2(3.3) in timolol group. In the apraclonidine group, significant reduction in the mean IOP started after 60 minutes (P= .005) and was still present after 24 hours (P < .001). In timolol group, IOP was reduced in the treated eyes, but this reduction was only significant in the treated eyes at T24h (P= .03). The highest reduction in IOP in timolol group was observed at T360 (21.0(2.2); 14.7%). Mean IOP was decreased prominently by apraclonidine compared to timolol in treated eyes. In conclusion, single dose of topical 0.5% apraclonidine reduced IOP significantly among normal horses in the present study. Further investigations are necessary for evaluating efficacy and safety of apraclonidine in horses.

Oral clonidine as a pre-anesthetic medication in hair transplantation surgery-A pilot study.

BACKGROUND: Hair transplantation (HT) is a safe and rewarding procedure for a patient as well as the surgeon. Clonidine may be a good adjuvant in HT because of its analgesic, anxiolytic, and sedative effects. OBJECTIVE: To study efficacy of Clonidine as a preoperative medication in HT. METHODS & MATERIALS: The study was a prospective trial of 46 consecutive patients who underwent HT between January and May 2017. Patients with normal vital parameters on arrival were given Tab clonidine (0.1 mg) 30 min before starting of the procedure [Clonidine group (n = 30)]; rest were included in the control group (n = 16). Vitals were monitored every 30 min during surgery until the end. Patients were assessed for pain, level of sedation during surgery and for postoperative analgesia. RESULT: All patients who received clonidine, except one, were comfortable and experienced no pain throughout the duration of surgery; nine went into deep sleep. Of the 16 patients in the control group, no patients reported deep sleep, 3 felt restless, and 4 had mild pain. There were no untoward effects in both groups. CONCLUSION: Our study suggests that clonidine is useful as a pre-anesthetic medication in HT. However, this is a pilot study and further larger studies are needed.

α-1 Adrenergic receptor antagonist doxazosin reverses hepatic stellate cells activation via induction of senescence.

BACKGROUND: Activated hepatic stellate cells (aHSCs) are the main effector cells during liver fibrogenesis. α-1 adrenergic antagonist doxazosin (DX) was shown to be anti-fibrotic in an in vivo model of liver fibrosis (LF), but the mechanism remains to be elucidated. Recent studies suggest that reversion of LF can be achieved by inducing cellular senescence characterized by irreversible cell-cycle arrest and acquisition of the senescence-associated secretory phenotype (SASP). AIM: To elucidate the mechanism of the anti-fibrotic effect of DX and determine whether it induces senescence. METHODS: Primary culture-activated rat HSCs were used. mRNA and protein expression were measured by qPCR and Western blot, respectively. Cell proliferation was assessed by BrdU incorporation and xCelligence analysis. TGF-ß was used for maximal HSC activation. Norepinephrine (NE), PMA and m-3M3FBS were used to activate alpha-1 adrenergic signaling. RESULTS: Expression of Col1α1 was significantly decreased by DX (10 µmol/L) at mRNA (-30 %) and protein level (-50 %) in TGF-ß treated aHSCs. DX significantly reduced aHSCs proliferation and increased expression of senescence and SASP markers. PMA and m-3M3FBS reversed the effect of DX on senescence markers. CONCLUSION: Doxazosin reverses the fibrogenic phenotype of aHSCs and induces the senescence phenotype.

Extracorporeal Membrane Oxygenation for COVID-19-Associated Multisystem Inflammatory Syndrome in a 5-year-old.

Severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) is associated with multisystem inflammatory syndrome in children (MIS-C) that ranges from mild symptoms to cardiopulmonary collapse. A 5-year-old girl presented with shock and a rapid decline in left ventricular function requiring intubation. SARS-CoV-2 was diagnosed by viral Polymerase Chain Reaction (PCR), and she received remdesivir and COVID-19 convalescent plasma. Initial echocardiogram (ECHO) demonstrated low normal left ventricular function and mild left anterior descending coronary artery dilation. She remained hypotensive, despite high-dose epinephrine and norepinephrine infusions as well as stress-dose hydrocortisone. Admission SARS-CoV-2 IgG assay was positive, meeting the criteria for MIS-C. An ECHO 9 hours after admission demonstrated a severe decline in left ventricular function. Due to severe cardiogenic shock, she was cannulated for venoarterial extracorporeal support (ECMO). During her ECMO course, she was treated with remdesivir, intravenous methylprednisolone, intravenous immunoglobulin, and anakinra. She was decannulated on ECMO day 7, extubated the following day, and discharged home 2 weeks later without respiratory or cardiac support. The use of ECMO for cardiopulmonary support for pediatric patients with MIS-C is feasible and should be considered early as part of the treatment algorithm for patients with severe cardiopulmonary dysfunction.

Successful treatment of the face post acne erythema using a topically applied selective alpha 1-Adrenergic receptor agonist, oxymetazoline 1.5%, a controlled left to right face comparative trial.

BACKGROUND: Post-inflammatory erythema (PIE) is a common sequalae of acne inflammation, persistent post acne erythema (PAE) is cosmetically unacceptable and sometimes its complete clearance could not be achieved. Oxymetazoline (OXZ) is a synthetic, direct-acting, sympathomimetic agonist that is highly selective for the 1α-adrenoceptor. It is a potent vasoconstrictor and well known for its ability to clinically 'get the red out'. AIM: The aim of this study was to evaluate the efficacy and safety of topical oxymetazoline (OXZ) 1.5% in treatment of post acne erythema (PAE) in a left to right face comparative study. METHODS: This study was conducted on 40 patients diagnosed with post acne erythema for at least 3 months, the left side of the face was treated with topical OXZ 1.5% in liposomal base and was compared to the right side to which topical lipogel was applied as a control. RESULTS: According to the investigator's global assessment of photographs and the analysis of erythema with image analysis software, topical OXZ was significantly effective in diminishing PAE when compared to topical placebo lipogel. CONCLUSION: Topical OXZ is a safe and effective treatment for post-acne erythema.

PRO AND CONTRA ON ADJUVANTS TO NEUROAXIAL ANESTHESIA AND PERIPHERAL NERVE BLOCKS.

Modern approach in surgical treatment and in managing acute and chronic pain is nowadays more and more based on the implementation of all possible techniques of regional anesthesia (RA). Local anesthetics (LA) are needed to achieve standard regional anesthesia. Local anesthetics are primarily characterized by time constraints and duration of action, and depending on the amount applied, adverse effects on the cardiac and central nervous system may occur. Adjuvants are drugs used together with LA due to their synergistic effect, i.e. they improve start latency and duration of sensory and motor blockade and enable reduction of cumulative dose of LA and reduction of adverse effects on cardiac and nervous system. Nowadays, there is a huge variety of drugs that can be administered in combination with LA, and they, in general, can be divided into opioid and non-opioid adjuvants. The administration of opioids in RA over an extended time period was accompanied by some negative characteristics as respiratory depression, nausea, vomiting. So, their usage is still under a special control. Due to the positive effects shown by drugs from non-opioid adjuvants group (e.g. adrenaline, alpha adrenergic agonists, steroids, magnesium, midazolam, ketamine etc.), indications for their administration broadened. However, there are still some restrains in clinical practice based on the fact that neurotoxicity and demonstration of neurological complications in regional anesthesia haven't been properly researched yet.

Selective activation of adrenoceptors potentiates IKs current in pulmonary vein cardiomyocytes through the protein kinase A and C signaling pathways.

Delayed rectifier K+ current (IKs) is a key contributor to repolarization of action potentials. This study investigated the mechanisms underlying the adrenoceptor-induced potentiation of IKs in pulmonary vein cardiomyocytes (PVC). PVC were isolated from guinea pig pulmonary vein. The action potentials and IKs current were recorded using perforated and conventional whole-cell patch-clamp techniques. The expression of IKs was examined using immunocytochemistry and Western blotting. KCNQ1, a IKs pore-forming protein was detected as a signal band approximately 100 kDa in size, and its immunofluorescence signal was found to be mainly localized on the cell membrane. The IKs current in PVC was markedly enhanced by both ß1- and ß2-adrenoceptor stimulation with a negative voltage shift in the current activation, although the potentiation was more effectively induced by ß2-adrenoceptor stimulation than ß1-adrenoceptor stimulation. Both ß-adrenoceptor-mediated increases in IKs were attenuated by treatment with the adenylyl cyclase (AC) inhibitor or protein kinase A (PKA) inhibitor. Furthermore, the IKs current was increased by α1-adrenoceptor agonist but attenuated by the protein kinase C (PKC) inhibitor. PVC exhibited action potentials in normal Tyrode solution which was slightly reduced by HMR-1556 a selective IKs blocker. However, HMR-1556 markedly reduced the ß-adrenoceptor-potentiated firing rate. The stimulatory effects of ß- and α1-adrenoceptor on IKs in PVC are mediated via the PKA and PKC signal pathways. HMR-1556 effectively reduced the firing rate under ß-adrenoceptor activation, suggesting that the functional role of IKs might increase during sympathetic excitation under in vivo conditions.

Otorhinolaryngological adverse effects of urological drugs

ABSTRACT Purpose: To describe the otorhinolaryngological adverse effects of the main drugs used in urological practice. Materials and Methods: A review of the scientific literature was performed using a combination of specific descriptors (side effect, adverse effect, scopolamine, sildenafil, tadalafil, vardenafil, oxybutynin, tolterodine, spironolactone, furosemide, hydrochlorothiazide, doxazosin, alfuzosin, terazosin, prazosin, tamsulosin, desmopressin) contained in publications until April 2020. Manuscripts written in English, Portuguese, and Spanish were manually selected from the title and abstract. The main drugs used in Urology were divided into five groups to describe their possible adverse effects: alpha-blockers, anticholinergics, diuretics, hormones, and phosphodiesterase inhibitors. Results: The main drugs used in Urology may cause several otorhinolaryngological adverse effects. Dizziness was most common, but dry mouth, rhinitis, nasal congestion, epistaxis, hearing loss, tinnitus, and rhinorrhea were also reported and varies among drug classes. Conclusions: Most of the drugs used in urological practice have otorhinolaryngological adverse effects. Dizziness was most common, but dry mouth, rhinitis, nasal congestion, epistaxis, hearing loss, tinnitus, and rhinorrhea were also reported. Therefore, doctors must be aware of these adverse effects to improve adherence to the treatment and to minimize damage to the health of patients.

Hitting the Vasopressor Ceiling: Finding Norepinephrine Associated Mortality in the Critically Ill.

BACKGROUND: There is no consensus on what dose of norepinephrine corresponds with futility. The purpose of this study was to investigate the maximum infusion and cumulative doses of norepinephrine associated with survival for patients in medical and surgical intensive care units (MICU and SICU). MATERIALS AND METHODS: A retrospective review was conducted of 661 critically ill patients admitted to a large academic medical center who received norepinephrine. Univariate, multivariate, and area under the curve analyses with optimal cut offs for maximum infusion rate and cumulative dosage were determined by Youden Index. RESULTS: The population was 54.9% male, 75.8% white, and 58.7 ± 16.1 y old with 384 (69.8%) admitted to the MICU and 166 (30.2%) admitted to the SICU, including 38 trauma patients. Inflection points in mortality were seen at 18 mcg/min and 17.6 mg. The inflection point was higher in MICU patients at 21 mcg/min and lower in SICU patients at 11 mcg/min. MICU patients also had a higher maximum cumulative dosage of 30.7 mg, compared to 2.7 mg in SICU patients. In trauma patients, norepinephrine infusions up to 5 mcg/min were associated with a 41.7% mortality rate. CONCLUSION: A maximum rate of 18 mcg/min and cumulative dose of 17.6 mg were the inflection points for mortality risk in ICU patients, with SICU patients tolerating lower doses. In trauma patients, even low doses of norepinephrine were associated with higher mortality. These data suggest that MICU, SICU, and trauma patients differ in need for, response to, and outcome from escalating norepinephrine doses.

Effects of omecamtiv mecarbil on failing human ventricular trabeculae and interaction with (-)-noradrenaline.

Omecamtiv mecarbil (OM) is a novel medicine for systolic heart failure, targeting myosin to enhance cardiomyocyte performance. To assist translation to clinical practice we investigated OMs effect on explanted human failing hearts, specifically; contractile dynamics, interaction with the ß1 -adrenoceptor (AR) agonist (-)-noradrenaline and spontaneous contractions. Left and right ventricular trabeculae from 13 explanted failing hearts, and trabeculae from 58 right atrial appendages of non-failing hearts, were incubated with or without a single concentration of OM for 120 min. Time to peak force (TPF) and 50% relaxation (t50% ) were recorded. In other experiments, trabeculae were observed for spontaneous contractions and cumulative concentration-effect curves were established to (-)-noradrenaline at ß1 -ARs in the absence or presence of OM. OM prolonged TPF and t50% in ventricular trabeculae (600 nM, 2 µM, p < .001). OM had no significant inotropic effect but reduced time dependent deterioration in contractile strength compared to control (p < .001). OM did not affect the generation of spontaneous contractions. The potency of (-)-noradrenaline (pEC50 6.05 ± 0.10), for inotropic effect, was unchanged in the presence of OM 600 nM or 2 µM. Co-incubation with (-)-noradrenaline reduced TPF and t50% , reversing the negative diastolic effects of OM. OM, at both 600 nM and 2 µM, preserved contractile force in left ventricular trabeculae, but imparted negative diastolic effects in trabeculae from human failing heart. (-)-Noradrenaline reversed the negative diastolic effects, co-administration may limit the titration of inotropes by reducing the threshold for ischemic side effects.

Adverse Events Associated with Intranasal Sprays: An Analysis of the Food and Drug Administration Database and Literature Review.

BACKGROUND: Intranasal sprays (INSs) are commonly used medications for the treatment of many rhinologic conditions. Despite their popularity, an analysis of a nationwide reporting database and comparison to the available literature has never been performed. METHODS: The Food and Drug Administration Adverse Event Reporting System (FAERS) database was accessed to obtain adverse event (AE) records from 2014 to 2019 for varying INSs, including: 10 corticosteroids, 1 alpha adrenergic, and 3 antihistamines. The Proportional Reporting Ratios (PRR) and Reporting Odds Ratios (ROR) were calculated for dyspnea, anosmia, ageusia/dysgeusia, epistaxis, and headache. A PRR ≥ 2 or ROR ≥ 1 was considered significant. RESULTS: Corticosteroids had 98 864 total reported AEs to the database, followed by antihistamines (7011) and alpha adrenergics (2071). In total, dyspnea was reported 5843 times, followed by headache (4230), epistaxis (1205), ageusia/dysgeusia (920), and anosmia (312). Overall, PRR and ROR values for dyspnea ranged from 0.51 to 4.25 and 0.51 to 4.49; for dysgeusia/ageusia from 0.56 to 6.09 and 0.56 to 6.12; and for epistaxis from 1.03 to 27.24 and 1.03 to 30.76, respectively. All medications which listed anosmia within the top AEs had PRR and ROR values exceeding 2 and 1, respectively. The PRR for headache exceeded 2 for 1 medication and the ROR exceeded 1 in 7 medications. CONCLUSION: The AEs of dyspnea, anosmia, ageusia/dysgeusia, epistaxis, and headache are reported within the FAERS database for commonly prescribed INSs. When compared against the existing scientific literature, the clinical significance of this reporting tool from the FDA for these classes of medications remains unvalidated.

Massive suicidal ingestion of caffeine: a case report with investigation of the cardiovascular effect/concentration relationships.

BACKGROUND: Caffeine poisoning may cause life-threatening arrhythmias and hemodynamic failure. We aimed to investigate the toxicokinetics (TK), toxicodynamics (TD) and TK/TD relationships of caffeine in a case of poisoning. CASE REPORT: A 47-year-old male ingested pure anhydrous caffeine powder (70 g) in a suicide attempt. He developed agitation, tachycardia, and two episodes of ventricular fibrillation treated with defibrillation and tracheal intubation. He was successfully managed using intravenous infusions of esmolol and norepinephrine. METHODS: We modelled the time-course of plasma caffeine concentration (TK study using online liquid chromatography-tandem mass spectrometry), the time-course of blood lactate concentration and infusion rates of esmolol and norepinephrine (TD studies) and the TK/TD relationships. RESULTS: Caffeine TK was of first-order peaking at 258 mg/L with an elimination half-life of 46.2 h and clearance of 2.2 L/h. Caffeine-related effects on blood lactate (peak, 10 mmol/L at 1.25 h postingestion) were described by a Bateman-type equation (formation rate, 0.05 mmol/mg.h; elimination rate, 0.9 mmol/mg.h). Esmolol and norepinephrine infusion rates to reverse caffeine-related cardiovascular effects (peaks at 51-h postingestion) fitted well with a sigmoidal Emax model (EC50, 180.0 and 225.9 mg/L, respectively; Hill coefficient, 10.0). CONCLUSION: Massive caffeine ingestion is characterized by prolonged caffeine elimination. TK/TD relationships are helpful to quantify caffeine-related catecholaminergic effects.