piperidines and Miosis

This study aimed to develop a model for pharmacodynamic and pharmacokinetic studies of naloxone antagonism under steady-state opioid agonism and to compare a high-concentration/low-volume intranasal naloxone formulation 8 mg/ml to intramuscular 0.8 mg.. Two-way crossover in 12 healthy volunteers receiving naloxone while receiving remifentanil by a target-controlled infusion for 102 min. The group were subdivided into three different doses of remifentanil. Blood samples for serum naloxone concentrations, pupillometry and heat pain threshold were measured.. The relative bioavailability of intranasal to intramuscular naloxone was 0.75. Pupillometry showed difference in antagonism; the effect was significant in the data set as a whole (p < 0.001) and in all three subgroups (p < 0.02-p < 0.001). Heat pain threshold showed no statistical difference.. A target-controlled infusion of remifentanil provides good conditions for studying the pharmacodynamics of naloxone, and pupillometry was a better modality than heat pain threshold. Intranasal naloxone 0.8 mg is inferior for a similar dose intramuscular. Our design may help to bridge the gap between studies in healthy volunteers and the patient population in need of naloxone for opioid overdose.. clinicaltrials.gov : NCT02307721.

Topics: Administration, Intranasal; Adult; Analgesics, Opioid; Cross-Over Studies; Female; Healthy Volunteers; Humans; Injections, Intramuscular; Male; Miosis; Models, Biological; Naloxone; Narcotic Antagonists; Pain; Piperidines; Pupil; Remifentanil; Young Adult

A novel clinical study design was used to evaluate the blockade of a selective short-acting μ-opioid agonist (remifentanil) in 24 opioid-experienced subjects. Samidorphan (3-carboxamido-4-hydroxynaltrexone) is a novel opioid modulator with μ-antagonist properties. Objective (pupil diameter) and subjective (visual analog scale) responses to repeated remifentanil and saline infusion challenges were assessed after single oral administration of placebo (day 1) and samidorphan (day 2). Complete blockade persisted with samidorphan for 24 hours for pupil miosis and 48 hours for the drug liking visual analog scale. Samidorphan effects persisted beyond measurable samidorphan exposure (t½ = 7 hours). Samidorphan was associated with complete blockade of remifentanil, and the duration supports daily administration. This study used a novel approach with multiple administrations of remifentanil to successfully demonstrate a durable effect with samidorphan and a rapid and potent blockade of physiological and subjective μ-opioid effects.

Topics: Adult; Analgesics, Opioid; Double-Blind Method; Female; Humans; Male; Middle Aged; Miosis; Naltrexone; Narcotic Antagonists; Piperidines; Receptors, Opioid, mu; Remifentanil; Visual Analog Scale; Young Adult

Peripheral mechanisms may be involved in opioid actions on the urinary bladder. This double-blind study investigated whether opioid inhibition of bladder function is reversed by methylnaltrexone, a peripheral opioid antagonist. Thirteen healthy male volunteers received an intravenous (i.v.) infusion of remifentanil, 0.15 mcg/kg/min, then a single i.v. dose of study medication (methylnaltrexone 0.3 mg/kg, naloxone 0.01 mg/kg, or saline). Urodynamics were measured with indwelling bladder and rectal catheters, and pupil size was assessed with infrared pupillometry. Remifentanil decreased detrusor pressure in 21/25 sessions and caused complete urinary retention in 18/25. Voiding was possible in 7/7, 5/12, and 0/6 sessions after naloxone, methylnaltrexone, and saline, respectively (P=0.0013). Remifentanil caused marked miosis that was reversed by naloxone, but not methylnaltrexone or placebo (P<0.0001). The pupil data confirm that methylnaltrexone did not reverse central opioid effects. Reversal of urinary retention by methylnaltrexone indicates that peripheral mechanisms may play a role in opioid-induced bladder dysfunction.

Topics: Adult; Analgesics, Opioid; Cross-Over Studies; Double-Blind Method; Humans; Infusions, Intravenous; Male; Middle Aged; Miosis; Muscle Contraction; Naloxone; Naltrexone; Narcotic Antagonists; Piperidines; Quaternary Ammonium Compounds; Remifentanil; Treatment Outcome; Urinary Bladder; Urinary Retention; Urination

Although cholinesterase inhibitors have been frequently used in the treatment of Alzheimer disease, its effects on serum cholinesterase concentrations have been rarely described. We described significant depression of serum cholinesterase levels due to cholinesterase inhibitor toxicity from redundant use of donepezil and rivastigmine in a 78-year-old man. Recovery of serum cholinesterase level was noted upon drug discontinuation and cholinergic symptom resolution. Serum cholinesterase level can be used as a biomarker for central cholinesterase inhibitor toxicity.

Topics: Aged; Bradycardia; Cholinesterase Inhibitors; Cholinesterases; Donepezil; Humans; Indans; Lewy Body Disease; Male; Miosis; Parkinson Disease; Phenylcarbamates; Piperidines; Rivastigmine

1. Inhibition of NK3 receptor agonist-induced contraction in the rabbit isolated iris sphincter muscle was used to assess the in vitro functional activity of three 2-phenyl-4-quinolinecarboxamides, members of a novel class of potent and selective non-peptide NK3 receptor antagonists. In addition, an in vivo correlate of this in vitro response, namely NK3 receptor agonist-induced miosis in conscious rabbits, was characterized with some of these antagonists. 2. In vitro senktide (succinyl-[Asp9,MePhe8]-substance P (6-11) and [MePhe7]-neurokinin B ([MePhe7]-NKB) were potent contractile agents in the rabbit iris sphincter muscle but exhibited quite different profiles. Senktide produced monophasic log concentration-effect curves with a mean pD2=9.03+/-0.06 and mean nH=1.2+/-0.02 (n=14). In contrast, [MePhe7]-NKB produced shallow log concentration-effect curves which often appeared biphasic (nH=0.54+/-0.04, n=8), preventing the accurate determination of pD2 values. 3. The contractile responses to the NK3 receptor agonist senktide were antagonized in a surmountable and concentration-dependent manner by SB 223412 ((-)-(S)-N-(alpha-ethylbenzyl)-3-hydroxy-2-phenylquinoline-4-ca rboxamide; 3-30 nM, pA2=8.4, slope=1.8+/-0.3, n=4). SB 222200 ((-)-(S)-N-(alpha-ethylbenzyl)-3-methyl-2-phenylquinoline-4-car box amide; 30-300 nM, pA2=7.9, slope=1.4+/-0.06, n=4) and SB 218795 ((-)-(R)-N-(alpha-methoxycarbonylbenzyl)-2-phenylquinoline-4-carboxamide; 0.3 and 3 microM apparent pKB=7.4+/-0.06, n=6). 4. Contractile responses to the NK3 receptor agonist [MePhe7]-NKB in the rabbit iris sphincter muscle were unaffected by SB 218795 (0.3 and 3 microM, n=8). In contrast, SB 223412 (30 and 300 microM n=4) and SB 222200 (0.3 and 3 microM, n=4) inhibited responses to low concentrations (< or = 1 nM), to a greater extent than higher concentrations (> 1 nM) of [MePhe7]-NKB. Furthermore, log concentration-effect curves to [MePhe7]-NKB became steeper and monophasic in the presence of each antagonist. 5. SB 218795 (3 microM, n=4) had no effect on contractions induced by transmural nerve stimulation (2 Hz) or substance P, exemplifying the selectivity of this class of antagonist for functional NK3 receptors over NK1 receptors in the rabbit. 6. In vivo, senktide (1, 10 and 25 microg i.v., i.e. 1.2, 11.9 and 29.7 nmol, respectively) induced concentration-dependent bilateral miosis in conscious rabbits (maximum pupillary constriction=4.25+/-0.25 mm; basal pupillary diameter 7.75+/-0.48 mm; n=4).

Topics: Animals; In Vitro Techniques; Iris; Male; Miosis; Muscle Contraction; Muscle, Smooth; Neurokinin B; Neurokinin-1 Receptor Antagonists; Peptide Fragments; Piperidines; Quinolines; Rabbits; Receptors, Neurokinin-3; Substance P

The muscarinic receptor subtype antagonists 4-diphenylacetoxy-N-methylpiperidine methobromide (4-DAMP), 11-[(2-[diethylamino)methyl]-1- piperidinyl)acetyl]-5,11-dihydro-6H-pyrido[2,3- b][1,4]benzodiazepine-6-one (AF-DX 116) and pirenzepine were used to inhibit the outflow facility and accommodative and miotic responses to near-maximal intracameral doses of pilocarpine in the living rhesus monkey eye. The pharmacologic M3 antagonist 4-DAMP was the most potent inhibitor of all three responses, with IC50 values of 41.7 nM for outflow facility (vs. 40.9 microM pilocarpine), 19.8 nM for accommodation (vs. 40.9 or 81.8 microM pilocarpine) and 3.2 nM for miosis (vs. 4.1 microM pilocarpine). The M1 antagonist pirenzepine was at least 30-fold less potent, with IC50 values of 2.2 microM for outflow facility, 1.4 microM for accommodation and 0.1 microM for miosis. The M2 antagonist AF-DX 116 was the least potent by far, with IC50 values of 15.5 microM for outflow facility, 14.2 microM for accommodation and 1.5 microM for miosis. The results suggest that these three functional responses to pilocarpine are all mediated through an M3 receptor subtype.

Topics: Accommodation, Ocular; Animals; Aqueous Humor; Female; Intraocular Pressure; Macaca mulatta; Male; Miosis; Muscarinic Antagonists; Parasympatholytics; Phenylephrine; Pilocarpine; Piperidines; Pirenzepine; Pupil