Pharmacokinetics and clinical effects of intramuscular scopolamine plus morphine. A comparison of two injection sites

The pharmacology of medieval sedatives: the "Great Rest" of the Antidotarium Nicolai

ETHNOPHARMACOLOGICAL RELEVANCE

Past practices of compound drugs from different plant ingredients enjoyed remarkable longevity over centuries yet are largely dismissed by modern science as subtherapeutic, lethal or fanciful.

AIM OF THE STUDY

To examine the phytochemical content of a popular medieval opiate drug called the "Great Rest" and gauge the bioavailability and combined effects of its alkaloid compounds (morphine, codeine, hyoscyamine, scopolamine) on the human body according to modern pharmacokinetic and pharmacodynamic parameters established for these compounds.

CALCULATIONS AND THEORY

We reviewed the most recent studies on the pharmacodynamics of morphine, codeine, hyoscyamine and scopolamine to ascertain plasma concentrations required for different physiological effects and applied these findings to dosage of the Great Rest.

RESULTS

Given the proportional quantities of the alkaloid rich plants, we calculate the optimal dose of Great Rest to be 3.1±0.1-5.3±0.76 g and reveal that the lethal dose of Great Rest is double the therapeutic concentration where all three alkaloid compounds are biologically active.

CONCLUSION

This study helps establish the effective dose (ED50), toxic dose (TD50) and lethal dose (LD50) rates for the ingestion of raw opium, henbane and mandrake, and describes their probable combined effects, which may be applied to similar types of pre-modern pharmaceuticals to reveal the empirical logic behind past practices.

The effect of site (deltoid or gluteus muscle) of intramuscular administration of anaesthetic drugs on the course of immobilisation in macaque monkeys (Macaca mulatta)

The aim of this work was to study the effect of site of intramuscular administration of anaesthetic drugs on the course of immobilisation in macaque monkeys (Macaca mulatta). Twenty macaque monkeys were given medetomidine (25 µg·kg-1) and ketamine (3 mg·kg-1) intramuscularly to the deltoid (n = 10 animals) or gluteus (n = 10 animals) muscles. Behavioural changes, loss of aggressiveness, immobilisation time and cardiorespiratory changes were recorded. The effect of drugs was reversed after 20 min by i.m. administration of atipamezole at the dose of 250 µg·kg-1. Highly significant differences (P < 0.001) were found between groups with gluteal or deltoid administration of drugs on the onset of immobilisation effect (71.3 s and 108.3 s, respectively), and immobilisation time (152.7 s and 254.4 s, respectively). In the gluteus muscle group, the grasp reflex was still present at the beginning of immobilisation and slowly wore off in 15–45 s. The same was valid for muscle tone. There were no differences in cardiorespiratory parameters in any of the groups. Animals of both groups recovered in 3–6 min after atipamezole administration. Administration of drugs to the deltoid muscle resulted in a more rapid onset and increased effect of immobilisation than administration to the gluteus muscle. Both in veterinary and human medicine, injection to the deltoid muscle may be more convenient in all cases, when rapid and more prominent effect is desirable as in premedication before surgery or in emergency medicine. The study is the first to compare the effect of administering drugs to different muscles and the results may improve the practice of intramuscular injections in animals and in humans.

Pharmacokinetics and pharmacodynamics in clinical use of scopolamine

The alkaloid L-(-)-scopolamine [L-(-)-hyoscine] competitively inhibits muscarinic receptors for acetylcholine and acts as a nonselective muscarinic antagonist, producing both peripheral antimuscarinic properties and central sedative, antiemetic, and amnestic effects. The parasympatholytic scopolamine, structurally very similar to atropine (racemate of hyoscyamine), is used in conditions requiring decreased parasympathetic activity, primarily for its effect on the eye, gastrointestinal tract, heart, and salivary and bronchial secretion glands, and in special circumstances for a CNS action. Therefore, scopolamine is most suitable for premedication before anesthesia and for antiemetic effects. This alkaloid is the most effective single agent to prevent motion sickness. Scopolamine was the first drug to be made commercially available in a transdermal therapeutic system (TTS-patch) delivering alkaloid. Recently, pharmacokinetic data on scopolamine in different biozlogic matrices were obtained most efficiently using liquid chromatographic-tandem mass spectrometric (LC-MS/MS) or gas chromatography online coupled to mass spectrometry. Pharmacokinetic parameters are dependent on the dosage form (oral dose, tablets; parenteral application; IV infusion; SC and IM injection). Scopolamine has a limited bioavailability if orally administered. The maximum drug concentration occurs approximately 0.5 hours after oral administration. Because only 2.6% of nonmetabolized L-(-)-scopolamine is excreted in urine, a first-pass metabolism is suggested to occur after oral administration of scopolamine. Because of its short half-life in plasma and dose-dependent adverse effects (in particular hallucinations and the less serious reactions, eg, vertigo, dry mouth, drowsiness), the clinical use of scopolamine administered orally or parenterally is limited. To minimize the relatively high incidence of side effects, the transdermal dosage form has been developed. The commercially available TTS-patch contains a 1.5-mg drug reservoir and a priming dose (140 microg) to reach the steady-state concentration of scopolamine quickly. The patch releases 0.5 mg alkaloid over a period of 3 days (releasing rate 5 microg/h). Following the transdermal application of scopolamine, the plasma concentrations of the drug indicate major interindividual variations. Peak plasma concentrations (Cmax) of approximately 100 pg/mL (range 11-240 pg/mL) of the alkaloid are reached after about 8 hours and achieve steady state. During a period of 72 hours the plaster releases scopolamine, so constantly high plasma levels (concentration range 56-245 pg/mL) are obtained, followed by a plateau of urinary scopolamine excretion. Although scopolamine has been used in clinical practice for many years, data concerning its metabolism and the renal excretion in man are limited. After incubation with beta-glucuronidase and sulfatase, the recovery of scopolamine in human urine increased from 3% to approximately 30% of the drug dose (intravenously administered). According to these results from enzymatic hydrolysis of scopolamine metabolites, the glucuronide conjugation of scopolamine could be the relevant pathway in healthy volunteers. However, scopolamine metabolism in man has not been verified stringently. An elucidation of the chemical structures of the metabolites extracted from human urine is still lacking. Scopolamine has been shown to undergo an oxidative demethylation during incubation with CYP3A (cytochrome P-450 subfamily). To inhibit the CYP3A located in the intestinal mucosa, components of grapefruit juice are very suitable. When scopolamine was administered together with 150 mL grapefruit juice, the alkaloid concentrations continued to increase, resulting in an evident prolongation of tmax (59.5 +/- 25.0 minutes; P < 0.001). The AUC0-24h values of scopolamine were higher during the grapefruit juice period. They reached approximately 142% of the values associated with the control group (P < 0.005). Consequently, the related absolute bioavailabilities (range 6% to 37%) were significantly higher than the corresponding values of the drug orally administered together with water (range 3% to 27%). The effect of the alkaloid on quantitative electroencephalogram (qEEG) and cognitive performance correlated with pharmacokinetics was shown in studies with healthy volunteers. From pharmacokinetic-pharmacodynamic modeling techniques, a direct correlation between serum concentrations of scopolamine and changes in total power in alpha-frequency band (EEG) in healthy volunteers was provided. The alkaloid readily crosses the placenta. Therefore, scopolamine should be administered to pregnant women only under observation. The drug is compatible with nursing and is considered to be nonteratogenic. In conclusion, scopolamine is used for premedication in anesthesia and for the prevention of nausea and vomiting associated with motion sickness. Pharmacokinetics and pharmacodynamics of scopolamine depend on the dosage form. Effects on different cognitive functions have been extensively documented.

Clinical pharmacokinetics of drugs used to treat urge incontinence

Urge incontinence (also known as overactive bladder) is a common form of urinary incontinence, occurring alone or as a component of mixed urinary incontinence, frequently together with stress incontinence. Because of the pathophysiology of urge incontinence, anticholinergic/antispasmodic agents form the cornerstone of therapy. Unfortunately, the pharmacological activity of these agents is not limited to the urinary tract, leading to systemic adverse effects that often promote nonadherence. Although the pharmacokinetics of flavoxate, propantheline, scopolamine, imipramine/desipramine, trospium chloride and propiverine are also reviewed here, only for oxybutynin and tolterodine are there adequate efficacy/tolerability data to support their use in urge incontinence. Oxybutynin is poorly absorbed orally (2-11% for the immediate-release tablet formulation). Controlled-release oral formulations significantly prolong the time to peak plasma concentration and reduce the degree of fluctuation around the average concentration. Significant absorption occurs after intravesical (bladder) and transdermal administration, although concentrations of the active N-desethyl metabolite are lower after transdermal compared with oral administration, possibly improving tolerability. Food has been found to significantly affect the absorption of one of the controlled-release formulations of oxybutynin, enhancing the rate of drug release. Oxybutynin is extensively metabolised, principally via N-demethylation mediated by the cytochrome P450 (CYP) 3A isozyme. The pharmacokinetics of tolterodine are dependent in large part on the pharmacogenomics of the CYP2D6 and 3A4 isozymes. In an unselected population, oral bioavailability of tolterodine ranges from 10% to 74% (mean 33%) whereas in CYP2D6 extensive metabolisers and poor metabolisers mean bioavailabilities are 26% and 91%, respectively. Tolterodine is metabolised via CYP2D6 to the active metabolite 5-hydroxymethyl-tolterodine and via CYP3A to N-dealkylated metabolites. Urinary excretion of parent compound plays a minor role in drug disposition. Drug effect is based upon the unbound concentration of the so-called 'active moiety' (sum of tolterodine + 5-hydroxymethyl-tolterodine). Terminal disposition half-lives of tolterodine and 5-hydroxymethyl-tolterodine (in CYP2D6 extensive metabolisers) are 2-3 and 3-4 hours, respectively. Coadministration of antacid essentially converts the extended-release formulation into an immediate-release formulation. Knowledge of the pharmacokinetics of these agents may improve the treatment of urge incontinence by allowing the identification of individuals at high risk for toxicity with 'usual' dosages. In addition, the use of alternative formulations (controlled-release oral, transdermal) may also facilitate adherence, not only by reducing the frequency of drug administration but also by enhancing tolerability by altering the proportions of parent compound and active metabolite in the blood.

Pharmacokinetics of Oxycodone After Intravenous, Buccal, Intramuscular and Gastric Administration in Children

OBJECTIVE

To evaluate the pharmacokinetics of four administration routes of oxycodone parenteral liquid (10 mg/mL), single intravenous and intramuscular injections and buccal and gastric administration, in children.

PATIENTS AND PARTICIPANTS

Forty generally healthy children, aged 6-93 months, undergoing inpatient surgery.

METHODS

After induction of anaesthesia, children received a single dose of oxycodone 0.1 mg/kg intravenously (n = 9), intramuscularly (n = 10), buccally (n = 11) or via an orogastric tube into the stomach (n = 10). Regular blood samples were collected up to 12 hours, and plasma was analysed for oxycodone using gas chromatography-mass spectrometry (limit of quantification 1 microg/L).

RESULTS

The peak drug concentration observed was 57-110 (mean 82) microg/L after intravenous administration, 23-54 (34) microg/L after intramuscular administration, 3.9-14 (9.8) microg/L after buccal administration and 1.7-15 (9.2) microg/L after gastric administration. The time to peak concentration was 2-30 (16) minutes in the intramuscular group, 30-480 (221) minutes in the buccal group and 60-360 (193) minutes in the gastric group. The terminal elimination half-lives were closely similar in the four groups: 124-208 (163) minutes in the intravenous group, 162-227 (150) minutes in the intramuscular group, 73-234 (150) minutes in the buccal group and 80-246 (147) minutes in the gastric group. Area under the concentration-time curve (AUC) was 5037-8954 (6612) microg x min/L in the intravenous group, 3084-5524 (4473) microg x min/L in the intramuscular group, 1444-5560 (3658) microg x min/L in the buccal group and 692-3843 (2436) microg x min/L in the gastric group. The estimated bioavailability (AUC/mean intravenous AUC) of intramuscular oxycodone was 0.47-0.84 (0.68), that of buccal oxycodone 0.22-0.84 (0.55) and that of gastric oxycodone 0.10-0.58 (0.37).

CONCLUSION

The pharmacokinetics of intravenous oxycodone in children aged 6-93 months are fairly similar to those reported in adults. Intramuscular administration provides relatively constant drug absorption, but after buccal and gastric administration the interindividual variation in the rate and extent of absorption is large.

Parenteral ketoprofen for pain management after adenoidectomy: comparison of intravenous and intramuscular routes of administration

BACKGROUND

Different parenteral routes of administration of NSAIDs such as ketoprofen have not been properly compared in children. This study was designed to compare the analgesic efficacy of intravenous and intramuscular ketoprofen for pain management in children after day-case adenoidectomy.

METHODS

A total of 120 children, aged 1-9 years, who were scheduled to undergo adenoidectomy, were randomized to receive ketoprofen 2 mg/kg either intravenously with intramuscular placebo (n = 40) or ketoprofen 2 mg/kg intramuscularly with intravenous placebo (n = 40), or both intravenous and intramuscular placebo (n = 40) at induction of anesthesia. The study design was prospective and double-blind with parallel groups. Pain was assessed at rest and during swallowing using the Maunuksela pain scale during 3 h after surgery, and fentanyl i.v. was given for rescue analgesia.

RESULTS

Children in the Placebo group needed significantly more doses of fentanyl (72 doses) than either children in the intravenous group (47 doses) or children in the intramuscular group (51 doses) (P = 0.021). In addition, a higher proportion of children in the Placebo group than in the two ketoprofen groups (P = 0.03) demanded rescue analgesic. No difference in the need for rescue analgesia or in pain scores was found between the two ketoprofen groups. Children in the intravenous group had less pain than children in the Placebo group. The difference was significant during swallowing at 1 h after surgery (P = 0.046) and for the worst pain observed during swallowing for 3 h after surgery (P = 0.022). There were no differences between the three groups with respect to operation times, amount of perioperative bleeding, or rate or extent of adverse events.

CONCLUSION

The efficacy of intravenous and intramuscular ketoprofen was similar, and they both differed from placebo.

Morphine, pethidine and buprenorphine disposition in the cat

Pharmacokinetics of morphine, buprenorphine and pethidine were determined in 10 cats. Six cats received morphine (0.2 mg/kg) intravenously and four intramuscularly. Five received buprenorphine (0.01 mg/kg) intravenously and six intramuscularly. Six received pethidine (5 mg/kg) intramuscularly. Jugular venous blood samples were collected at time points to 24 h, and plasma morphine concentrations were measured by high performance liquid chromatograpy (HPLC), buprenorphine by radioimmunoassay (RIA) and pethidine by gas chromatography. Our data for morphine show elimination half-life (t1/2el) 76.3 min intravenous (i.v.) and 93.6 min intramuscular (i.m.); mean residence time (MRT) 105.0 and 120.5 min; clearance (Clp) 24.1 and 13.9 mL/kg/min; and volume of distribution (V(dss)) 2.6 and 1.7 L/kg, respectively. Comparable data for buprenorphine are t1/2el 416.8 and 380.2 min; MRT 417.6 and 409.8 min; Clp 16.7 and 23.7 mL/kg/min; and V(dss) 7.1 and 8.9 L/kg. For i.m. pethidine, t1/2el 216.4 min; MRT 307.5 min; Clp 20.8 mL/kg/min and V(dss) 5.2 L/kg. For i.m. dosing, the tmax for morphine, buprenorphine and pethidine were 15, 3 and 10 min, respectively. The pharmacokinetics of the three opioids in cats are broadly comparable with those of the dog, although there is a suggestion that the cat may clear morphine more slowly.