Anticholinergic premedication in Finland 1988

Pharmacokinetics and oral bioavailability of glycopyrrolate in children

Based on plasma levels determined with a radioreceptor assay and following a single oral (50 micrograms/kg) and intravenous (5 micrograms/kg) administration of glycopyrrolate in six healthy children operated twice during a several weeks period, a negligible and variable oral bioavailability was found (3.3; 1.3-13.3%) (median;range). No significant changes in heart rate after oral or intravenous administration of the drug could be seen. Oral glycopyrrolate appears to have no place in paediatric premedication.

Pharmacological premedication for anaesthesia

The psychological component of preoperative preparation should be completed with a selective use of drugs. The days of poly-pharmacy are over. Heavily sedated patients coming to the operation room with minimal oral secretions are not the purpose of modern premedication. Anxiolysis and slight sedation (painless patients) and analgesia (patients suffering from pain) are the main goals. Anticholinergics should be used only when needed, as is the case with premedication generally. The use of antiemetics and that of agents given for prophylaxis against allergic reactions or aspiration pneumonitis depend on specific needs of the patient. More accurate and generally accepted but simple methods are needed in studying the effects of different premedicants. The present results produced with a huge number of different more or less validated assessments can seldom be compared with each other.

Preoperative glycopyrrolate: oral, intramuscular, or intravenous administration

STUDY OBJECTIVE

To evaluate the effects of oral, intramuscular (i.m.) and intravenous (i.v. glycopyrrolate on oral and gastric secretions, and to assess how these routes of administration change intubating conditions.

DESIGN

Randomized, double-blinded study.

SETTING

University hospital operating room.

PATIENTS

37 ASA status I and II general anesthesia patients.

INTERVENTIONS

Patients were randomized to receive glycopyrrolate or placebo just before surgery by three routes: oral, i.m., and i.v.. Glycopyrrolate was received once by one route and placebo by the other two routes. A placebo group received three placebos and no glycopyrrolate.

MEASUREMENTS AND MAIN RESULTS

Mouth conditions and intubating conditions were qualitatively assessed by the patient and the intubating anesthesiologist. No difference between groups was noted. Oral and gastric volumes were measured and showed significantly less gastric volume for the i.v. group as compared with the other groups. Oral secretions were reduced in both the i.v. and i.m. groups when compared with placebo or glycopyrrolate administered orally.

CONCLUSIONS

Preoperative glycopyrrolate is significantly more effective at reducing oral and gastric secretions if administered intravenously immediately before induction.

A placebo-controlled trial using intravenous atropine as an adjunct to conscious sedation in pediatric esophagogastroduodenoscopy

BACKGROUND

The usefulness of intravenous atropine as an adjunct to conscious sedation in pediatric esophagogastroduodenoscopy remains an unresolved issue.

METHODS

This prospective, double-blind, randomized study examined 101 patients, who were randomized to receive either intravenous atropine 0.02 mg/kg (maximum 0.4 mg) or a placebo of normal saline solution prior to the procedure.

RESULTS

The mean maximum heart rate during the procedure and the percentage of time that the heart rate was more than 1 standard deviation above mean for age was significantly greater in the atropine group as compared to the placebo group (p < 0.0005). There was no significant difference between groups in the amount of secretions noted, gastric motility, retching or vomiting, facial flushing, or dysphoria. There were no causes of significant bradycardia or hypotension in either group. There was a significant number of patients greater than 5 years of age and receiving meperidine and atropine (as compared with meperidine and placebo) whose arterial oxygen saturation dropped below 90% during the procedure (p = 0.0485).

CONCLUSIONS

We found that the use of atropine when used as an adjunct to conscious sedation in children undergoing upper endoscopy did not increase the safety of the procedure or provide significant benefits. We do not recommend the routine use of atropine for upper endoscopy in pediatric patients.

Pharmacokinetics and related pharmacodynamics of anticholinergic drugs

The pharmacokinetics and some pharmacodynamic properties of atropine, glycopyrrolate and scopolamine are reviewed. With the development of new analytical methods for drug determination, it is now possible to measure relatively low concentrations of these drugs in biological fluids and, consequently, some new kinetic data have been collected. Following intravenous administration, a fast disappearance from the circulation is observed and due to a high total clearance value their elimination phase half-lives vary from 1 to 4 h. All these agents are nonselective muscarinic receptor antagonists, but their actions on various organ systems with cholinergic innervation show considerable diversity. The cardiovascular effects are of short duration; other peripheral muscarinic effects and CNS effects can last up to 8 h or even longer. Differing from atropine and scopolamine, glycopyrrolate as a quaternary amine penetrates the biological membranes (blood-CNS, placental barriers) slowly and incompletely, making it the drug of choice for elderly patients with coexisting diseases and for obstetric use. Similarly, its oral absorption is slow and erratic, and hence it cannot be used as an oral premedicant. Atropine, scopolamine and glycopyrrolate have a definitely faster absorption rate, when injected into the deltoid muscle compared with administration into the gluteal or vastus lateralis muscles. There appear to be significant differences in the metabolism and renal excretion of these agents. Scopolamine is apparently excreted into the urine mainly as inactive metabolites, nearly half of the atropine dose administered is recovered in the urine as the parent drug or as active metabolites and about 80% of glycopyrrolate is excreted as unchanged drug or active metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Glycopyrronium bromide blocks differentially responses mediated by muscarinic receptor subtypes

To analyse the potency of glycopyrronium bromide in blocking responses mediated via subtypes of muscarinic receptors in vitro, we tried to determine its equilibrium dissociation constants at prejunctional muscarinic receptors inhibiting the twitch response of rabbit vas deferens (presumed M1 type), at M2 (paced at left atria), M3 (guinea pig ileum) muscarinic receptor subtypes and at the muscarinic receptor of the rabbit iris sphincter (not M1-M4, not m5). Glycopyrronium bromide shifted to the right the curve for inhibition of the twitch response induced by the agonist McN-A-343, and the methacholine-induced curves for inhibition of rat atrial contraction, and for tonic contraction of guinea pig ileum and rabbit iris sphincter. Glycopyrronium bromide blocked with very high potency (> 11, apparent -log KB) the response in rabbit vas deferens. Its affinity was low (9.09) for the M2 subtype, and intermediate (10.31 or 10.13) for the ileal M3 and the atypical iris muscarinic receptor subtype, respectively. Except at the receptors in rabbit vas deferens, the blockade of agonist effect appeared to be of simple competitive type. In conclusion, glycopyrronium bromide is about 10 or 100 fold more potent in preventing a response to activation of the prejunctional receptor in rabbit vas deferens than in blocking an M3 or M2 muscarinic receptor subtype, respectively, in vitro. The low affinity for M2 receptors may, in part, explain the low incidence of unwanted tachycardia in therapy. The drug failed to discriminate between an M3 receptor and the atypical rabbit iris sphincter receptor.

Do anticholinergic agents affect the occurrence of postanaesthetic nausea?

In order to establish if anticholinergic drugs might influence postoperative nausea and vomiting, 100 ASA I-II adult patients scheduled for minor orthopaedic procedures, varicose vein stripping or inguinal herniorraphy were randomised to receive, in a double-blind fashion, either a premedicant and a reversal dose of 0.003 and 0.0075 mg/kg of glycopyrrolate or 0.006 and 0.015 mg/kg of atropine, respectively. Nitrous oxide, after thiopentone induction was used for anaesthesia with fentanyl and diazepam as supplements and pancuronium for relaxation. In the recovery room, up to 2 h after surgery, 28% of the patients in the glycopyrrolate group and 8% in the atropine group experienced nausea (P = 0.017). Thereafter, the patients complained of nausea at decreased and equal frequencies in both groups. The incidence of vomiting was not statistically significantly different. Droperidol was needed, to control persistent emesis, three times more often in the glycopyrrolate than in the atropine group. It is concluded that substitution of glycopyrrolate for atropine increases the likelihood of postoperative nausea, and continued use of atropine should be considered in patients at risk of postoperative emesis.

Glycopyrrolate: pharmacokinetics and some pharmacodynamic findings

In the present study, a sensitive and reproducible radioreceptor assay (RRA) was used to evaluate the basic pharmacokinetic properties of glycopyrrolate, a quaternary amine with peripheral antimuscarinic activity. Based on the plasma levels after a single intravenous injection, 6 micrograms/kg (n = 6), the distribution phase half-life (2.22 +/- 1.26 s.d. min) and the elimination phase half-life (0.83 +/- 0.29 h) of glycopyrrolate were short due to the low distribution volume during the elimination phase (0.64 +/- 0.29 l/kg) and to the respectively high total plasma clearance value (0.54 +/- 0.14 l/kg/h). An intramuscular injection, 8 micrograms/kg (n = 6), was followed by a fast and predictable systemic drug absorption and clinical effects (heart rate increase, dry mouth). In this group the time to maximum plasma concentration (tmax) was 27.48 +/- 6.12 min and the maximum plasma concentration (Cmax) was 3.47 +/- 1.48 micrograms/l. After oral drug intake, 4 mg (n = 6), an apparently low and variable gastrointestinal absorption was found (tmax = 300.0 +/- 197.2 min, Cmax = 0.76 +/- 0.35 microgram/l), thus indicating that the oral route of drug administration is of no value as a routine premedication. The correlation between the plasma concentration of glycopyrrolate and the drug effects appears to be variable. Because of its sensitivity, the RRA method proved to be quite useful in evaluating the kinetics of glycopyrrolate and its relationship to various clinical effects.