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PubMed1992

The influence of gastrointestinal transit on drug absorption in healthy volunteers.

1. The effect of variability of gastric emptying and oro-caecal transit on the absorption of a multicomponent solution of frusemide, atenolol, hydrochlorthiazide and salicylic acid has been studied in six healthy subjects. Each subject was studied on five separate occasions: three times under basal conditions, once following metoclopramide and once following codeine pretreatment in an attempt to speed and slow transit respectively. 2. Inter-subject variability of gastric emptying, oro-caecal transit and the rate and extent of drug absorption was considerable. 3. The absorption of salicylic acid appeared rate-limited by gastric emptying but the rate and extent of frusemide, atenolol and hydrochlorthiazide absorption were unrelated to measures of gastric emptying or oro-caecal transit. 4. Codeine phosphate caused a two-fold delay in oro-caecal transit but did not influence gastric emptying while metoclopramide had no significant effect on either function. 5. Metoclopramide and codeine had no significant effect on the rate or extent of absorption of any of the study drugs. 6. Within the limits of this experiment, oro-caecal transit time did not appear to be an important determinant of frusemide, atenolol, hydrochlorothiazide or salicylic acid absorption. Other factors must account for the observed variability in drug absorption.

Administration, Oral↗
PubMed1995

Methacholine induces wheal-and-flare reactions in human skin but does not release histamine in vivo as assessed by the skin microdialysis technique.

A number of investigations have indicated that cholinergic agonists release histamine from isolated mast cells and suggested that cholinergic stimulation releases histamine in vivo. The purpose of this study was to investigate whether the cutaneous wheal-and-flare reaction induced by methacholine challenge in human skin involves histamine release as measured by the skin microdialysis technique. Five hollow dialysis fibers were inserted intradermally in forearm skin in eight healthy subjects. Each fiber was perfused with Kreb's-Ringer bicarbonate at a rate of 3 microliters/min. Dialysates were collected in 2-min fractions before skin challenge and for 20 min after intradermal injection of methacholine 10(-3)-10(-1) M, the vehicle, and a positive control, codeine phosphate 0.3 mg/ml. Histamine was assayed spectrofluorometrically. Methacholine caused a statistically significant dose-related wheal-and-flare reaction, the flare reaction to methacholine 10(-1) M being comparable with that seen with codeine 0.3 mg/ml. No significant histamine release was observed with methacholine, cumulative histamine release of 16 +/- 8 nM by methacholine 10(-1) M being similar to vehicle responses of 15 +/- 9 nM. Histamine release by codeine was 2524 +/- 435 nM. In conclusion, methacholine-induced wheal-and-flare reactions in human skin appeared not to involve histamine release from skin mast cells.

Adult↗
PubMed1969

Comparison of effect of morphine-like analgesics on transmurally stimulated guinea-pig ileum.

1. Morphine-like analgesic drugs caused depression of twitches of the isolated guinea-pig ileum in response to transmural electrical stimulation. The drugs tested were the narcotic analgesics codeine, diamorphine, fentanyl, morphine, morphine-N-oxide, normorphine, oxymorphone, pethidine, phenazocine and phenoperidine and the analgesic narcotic antagonists nalorphine and pentazocine.2. With the first application of one of these drugs the extent of depression of twitches was proportional to concentration. Except in the case of pethidine, there was no further depression when additional drug was added to the organ bath. With the second application of a drug after washing out the first dose, the depressant effect was less; that is, tolerance developed. With pethidine, the depression of twitches was proportional to concentration and tolerance could not be observed.3. When tolerance had been produced by cumulative addition of these drugs, a concentration was reached at which further addition resulted in increased activity of the ileum.4. With codeine, morphine and normorphine, the twitches were increased in height and regular.5. With diamorphine, fentanyl, oxymorphone, pentazocine, phenazocine and phenoperidine there were increased but irregular responses to transmural stimulation.6. Having reached the concentration at which these effects were observed, washout of the drug resulted in reduction of activity; the twitches became smaller or the irregular responses ceased.7. Readministration of a drug after activity of the ileum had been depressed by withdrawal of that drug resulted in restoration of activity, the ileum being dependent on the presence of the drug for its activity.8. Codeine and nalorphine did not produce as great an increase in activity on readministration to a dependent ileum as did morphine: they seem to act as partial agonists in producing this effect.9. In similar experiments with the isolated urinary bladder of the rat and guinea-pig, morphine was less active in depressing responses to stimulation than it was on the ileum, and tolerance to the drug and dependence on it did not occur.10. These observations have been discussed in relation to analgesic activity, tolerance and dependence in man.

Analgesics↗
PubMed1992

Capsaicin-induced bronchoconstriction in the guinea-pig: contribution of vagal cholinergic reflexes, local axon reflexes and their modulation by BW443C81.

1 The objective of the study was to investigate the central vagal and local axon reflex components of bronchoconstrictor responses evoked by inhalation of capsaicin aerosol in anaesthetized guinea-pigs. This was accomplished by comparing the effects of bilateral vagotomy, atropine and the peripherally-acting polar enkephalin analogue, BW443C81, on bronchoconstrictor responses evoked by capsaicin. The effects of codeine were also determined. 2 Aerosols of capsaicin were generated from a 0.9 microgram ml-1 solution. Inhalation of capsaicin aerosol in 5, 10 and 15 breaths evoked dose-related bronchoconstrictor responses. The responses were immediate in onset and of extended duration. 3 Capsaicin-induced bronchoconstrictor responses were significantly inhibited following bilateral vagotomy or atropine (0.3 mg kg-1, i.v.) pretreatment by 46% +/- 14% (P less than 0.05) and 59% +/- 13% (P less than 0.01), respectively. 4 Administration of BW443C81 by intravenous infusion (3, 30 and 100 micrograms kg-1 min-1) caused a significant inhibition of capsaicin-induced bronchoconstrictor responses which achieved a greater maximum than either bilateral vagotomy or atropine. Codeine (100 micrograms kg-1 min-1, i.v.) did not significantly inhibit the bronchoconstrictor responses. 5 Inhibition of capsaicin-induced bronchoconstrictor responses by BW443C81 (30 micrograms kg-1 min-1, i.v.) was significantly (P less than 0.05) reduced by the peripherally-acting opioid antagonist N-methyl nalorphine (100 micrograms kg-1 min-1, i.v.). 6 These results show that capsaicin-induced bronchoconstrictor responses are mediated by at least two mechanisms, a vagal and/or cholinergic reflex pathway and a non-cholinergic pathway. BW443C81, but not codeine, significantly inhibited (P < 0.005) both mechanisms of capsaicin-induced bronchoconstriction probably by an action on peripheral opioid receptors located on vagal sensory nerves.

Amino Acid Sequence↗
PubMed2006

Expression, purification, and characterization of mouse CYP2d22.

Metabolism of the prototype human CYP2D6 substrates debrisoquine and bufuralol proceeds at a much slower rate in mice; therefore, the mouse has been proposed as an animal model for the human CYP2D6 genetic deficiency. To interpret the molecular mechanism of this deficiency, a cDNA belonging to the CYP2D gene subfamily (Cyp2d22) has been cloned and sequenced from a mouse mammary tumor-derived cell line. In the current study, Cyp2d22 enzyme was overexpressed and purified from insect cells using a baculovirus-mediated system. The activity of this purified enzyme was directly compared with purified human CYP2D6 toward codeine, dextromethorphan, and methadone as substrates. Purified Cyp2d22 was found to catalyze the O-demethylation of dextromethorphan with significantly higher K(m) values (250 microM) than that (4.2 microM) exhibited by purified human CYP2D6. The K(m) for dextromethorphan N-demethylation by Cyp2d22 was found to be 418 microM, much lower than that observed with human CYP2D6 and near the K(m) for dextromethorphan N-demethylation catalyzed by CYP3A4. CYP2D6 catalyzed codeine O-demethylation, whereas Cyp2d22 and CYP3A4 mediated codeine N-demethylation. Furthermore, methadone, a known CYP3A4 substrate and CYP2D6 inhibitor, was N-demethylated by Cyp2d22 with a K(m) of 517 microM and V(max) of 4.9 pmol/pmol/min. Quinidine and ketoconazole, potent inhibitors to CYP2D6 and CYP3A4, respectively, did not show strong inhibition toward Cyp2d22-mediated dextromethorphan O- or N-demethylation. These results suggest that mouse Cyp2d22 has its own substrate specificity beyond CYP2D6-like-deficient activity.

Amino Acid Sequence↗
PubMed2003

Antinociceptive synergy between delta(9)-tetrahydrocannabinol and opioids after oral administration.

The analgesic effects of opioids, such as morphine and codeine, in mice are enhanced by oral administration of the cannabinoid delta(9)-tetrahydrocannabinol (delta(9)-THC). However, isobolographic analysis has never been done to confirm a synergy between delta(9)-THC and morphine or codeine via oral routes of administration. To determine the nature of the interaction between these drugs for pain relief and extend previous experimental results, we performed an isobolographic analysis to evaluate for additivity or synergy in the tail-flick test. Fixed-ratio combinations of delta(9)-THC with either morphine or codeine were tested for antinociceptive effects. The experimentally derived ED(50) for each combination was compared with the theoretical additive ED(50), using an isobolographic analysis. All of the fixed-ratio combinations tested produced greater antinociception (synergy) than predicted from simple additivity. These findings suggest that the use of a low-dose combination of analgesics is a valid and effective approach for the treatment of pain and necessitates further study.

Administration, Oral↗
PubMed1998

Pulmonary disposition of lipophilic amine compounds in the isolated perfused rabbit lung.

We measured the pulmonary venous concentration vs. time curves for [3H]alfentanil, [14C]lidocaine, and [3H]codeine after the bolus injection of each of these lipophilic amine compounds (LAC) and a vascular-reference indicator (fluorescein isothiocyanate-dextran) into the pulmonary artery of isolated perfused rabbit lungs. A range of flows and perfusate albumin concentrations was studied. To evaluate the information content of the data, we developed a kinetic model describing the pulmonary disposition of these LAC that was based on indicator dilution theory, and we sought a robust approach for interpreting the estimated model parameters. We found that the distribution of the kinetic model rate constants of the lipophilic amine-tissue interactions can be described by alpha, H, and psi, where alpha is a measure of the capacity of the rapidly equilibrating interactions between the lipophilic amine and the tissue; H is a measure of the equilibrium capacity of the slowly equilibrating interactions between the lipophilic amine and the tissue; and psi is the mean sojourn time. The values of alpha, H, and psi were 0.8 +/- 0.1 (SE), 0.6 +/- 0.1, and 1.6 +/- 0.5 s; 1.9 +/- 0.1, 5.3 +/- 0.4, and 5.6 +/- 0.5 s; and 1.1 +/- 0.1, 9.8 +/- 0.4, and 4.7 +/- 0.2 s for alfentanil, lidocaine, and codeine, respectively. These values for alpha, H, and psi reveal the relative dominance of the slowly equilibrating interactions for lidocaine and codeine in comparison with alfentanil. This approach to data analysis may have utility for the potential use of LAC to reveal and to quantify changes in lung tissue composition associated with lung disease.

Alfentanil↗
PubMedDate not supplied

Pharmacological stimuli in asthma/urticaria.

BACKGROUND: The use of opioids as analgesics is becoming increasingly widespread, which may have repercussions in patients with urticaria or asthma, as these agents frequently cause adverse reactions. MATERIAL AND METHODS: We present three patients who developed allergic reactions after receiving codeine: two patients who developed acute urticaria, and a third asthmatic patient receiving specific immunotherapy who developed bronchospasm. Skin prick-testing (SPT) and intradermal reaction (IDR) tests with various opioids were performed, followed by controlled oral challenge. Prick tests and IDR were also carried out in 20 controls. RESULTS: Similar SPT and IDR results were recorded in the three patients and in the controls. In the case of controlled oral challenge with codeine, patient 1 suffered bronchospasm, while patient 2 developed generalized urticaria. The test was not performed in the third patient. All of the patients tolerated tramadol 50 mg without problems. We advised the use of tramadol as analgesic and fentanyl or remifentanil as anesthetics. DISCUSSION: In these types of manifestation, the pharmacological properties of the opioids used are highly important, particularly as regards their histamine-releasing potential. Codeine, morphine and pethidine present the greatest histamine-releasing capacity, while tramadol, fentanyl and remifentanil do not release histamine and their use is thus recommended in pulmonary disease requiring opioid administration. Cutaneous symptoms are more frequently caused by opioids than by respiratory symptoms, since these drugs act on the MTC mast cell population, which is more prevalent in the skin than in the lungs. Some of this action is inhibited by naloxone. CONCLUSIONS: In most patients, these reactions are not IgE-mediated. Consequently, SPT and IDR are of little diagnostic value, and controlled oral challenging with the suspect drug or with one of the non-histamine releasing agents should be used. The patch test is useful in occupational contact dermatitis.

Adult↗
PubMed2000

Effect of short-term ketorolac infusion on recovery following laparoscopic day surgery.

This study tested the hypothesis that, by the addition of parenteral ketorolac to an oral analgesic regimen for one day following laparoscopic surgery, analgesia would be improved and thus the return of normal function hastened. Seventy-two female patients were randomly assigned to receive ketorolac 10.5 mg subcutaneously at the end of surgery followed by a subcutaneous infusion of 1.75 mg/h for 24 to 36 hours, or an equivalent volume of saline. All patients were provided with codeine tablets (30 mg) for analgesia if required. For the first four postoperative days patients recorded details of pain, side-effects and discomfort on performing everyday activities. Patients who received ketorolac received significantly less fentanyl in the Recovery Ward and significantly less codeine prior to discharge than the saline group. They also took significantly fewer codeine tablets over the four-day postoperative period. Pain scores in the ketorolac group were not significantly lower than in the saline group on the first postoperative day (P = 0.052) and subsequently remained similar. Levels of discomfort on performing six common activities were similar in the two groups over the four-day postoperative period. We conclude that, despite beneficial effects during the period of ketorolac administration, there was no continuing benefit after this time other than reduced analgesic use, and no improvement in the patients' ability to perform common activities.

Adolescent↗
PubMed2005

Opioid purchases and expenditure in nine western European countries: 'are we killing off morphine?'.

BACKGROUND: In clinical practice the major role of opioid drugs is the management of malignant and nonmalignant pain. The primary aim of this study is to evaluate the trend in sales of four opioid analgesic drugs (codeine, tramadol, morphine, fentanyl), from wholesalers to community pharmacies, as an indicator of opioid consumption in nine European countries in 2001, 2002 and 2003. Secondary aims are to compare: (a) the amount of each drug purchased by different countries in 2003; (b) the average price for each drug in the different countries in 2003; and (c) the total expenditure for each opioid from 2001 to 2003. METHODS: Data from the Statistical Report on drugs purchased by pharmacies was supplied by IMS Health, an internationally accepted information provider for the pharmaceutical and health care industries. FINDING: In the period 2001 2003, while the percentage increase of purchases of fentanyl and tramadol was considerable, that of morphine was the lowest in most of the nine countries. The largest consumer of codeine was the UK and of tramadol was Belgium. The consumption of morphine was the lowest reported in all the countries together and was three times lower than that of transdermal fentanyl. There was a high variability in the costs of the opioids among the different countries. In 2003, the total expenditure for fentanyl reached the highest total expenditure [corrected] followed by codeine. Morphine presents the lowest expenditure in all nine countries and over all three years. INTERPRETATION: These results open up many questions. What factors influence opioid purchasing and costs in these European countries? It would be interesting to have the answers from those people who know the actual situation in the individual countries.

Codeine↗
PubMed1975

The role of bronchoconstriction in cough reflex.

To investigate the role of bronchoconstriction in the cough reflex, we compared antitussive effects of several drugs with their ability to effect the respiratory tract (i.e. bronchodilation vs. bronchoconstriction). Antitussive activities of five drugs administered either intravenously or orally on electrically-induced cough were evaluated in the non-anesthetized dog. The antitussive activities were as follows: morphine, 0.1 mg/kg (i.v.) and 0.5 mg/kg (p.o.); codeine, 1.0, 4.0; picoperidamine, 2.0, 9.8; piclobetol, 7.6, 9.0; HH-197, 12.5, 143.0, respectively. Morphine, codeine and HH-197 caused bronchoconstriction, but picoperidamine and picrobetol caused bronchodilation. The antitussive and bronchodilatation effects of isoproterenol were abolished by propranolol. Each bronchoconstricting drug (i.e. morphine, codeine and HH-197) was administered concurrently with isoproterenol (10 mug/kg, i.v., and non-antitussive activity), and the cough reflex was observed. Compared with the single administration of each drug, respiratory resistance was decreased and the antitussive effect was increased. These results indicate a strong correlation between bronchodilatation and increased antitussive activity.

Airway Resistance↗
PubMed2006

Does celecoxib potentiate the anticoagulant effect of warfarin? A randomized, double-blind, controlled trial.

BACKGROUND: The management of patients who are receiving warfarin therapy and have musculoskeletal problems that require treatment with a nonsteroidal antiinflammatory drug (NSAID) is problematic because NSAID use may increase the risk for bleeding. Cyclooxygenase-2 selective NSAIDs such as celecoxib may be less likely to promote gastrointestinal bleeding; however, there are concerns that they could potentiate the anticoagulation effect of warfarin. OBJECTIVE: To determine whether celecoxib potentiates the anticoagulant effect of warfarin, as measured by the international normalized ratio (INR). METHODS: We performed a randomized, controlled, crossover trial to assess the effect on INR of celecoxib versus codeine (control treatment) in 15 patients who were receiving warfarin therapy and required analgesic treatment for osteoarthritis. During Phase 1 of the study, patients were randomly allocated to receive celecoxib 200 mg/day or codeine phosphate 7-15 mg 3-4 times daily for 5 weeks. During Phase 2 of the study, patients stopped the first study medication and started the other study medication; there was no drug-free interval between phases. Weekly INR testing was performed during the 10 week study period. Adopting the intent-to-treat principle, we used generalized estimating equations to analyze the data. RESULTS: There was no significant difference in the mean INR values during each 5 week treatment period when patients received either celecoxib or codeine. There was, therefore, insufficient evidence to reject the hypothesis that these 2 treatments had an equal effect on the INR (mean difference [95% CI] 0.10 [-0.04 to 0.24]; p = 0.16) based on mean imputation. This finding was confirmed after we repeated the analysis with multiple imputations (mean difference [95% CI] 0.093 [-0.16 to 0.35]; p = 0.47). CONCLUSIONS: Our results suggest that treatment with celecoxib does not potentiate the INR when taken with warfarin. Larger randomized trials are warranted to address the effects of coadministered warfarin and celecoxib on clinical outcomes.

Aged↗
PubMed2000

Utilization of common analgesic and anxiolytic medications by registered First Nations residents of western Canada.

The study examined utilization of acetaminophen with codeine and benzodiazepine drugs among Non-Insured Health Benefits (NIHB) program registered First Nations residents in the four western provinces of Canada and sought preliminary indicators of factors influencing utilization. A small percentage of NIHB clients in the four western provinces were excessive users of acetaminophen with codeine and/or benzodiazepines, but overall utilization of these central nervous system drugs was moderate and within the bounds of non-First Nations population use examined in this study. The study also demonstrated that utilization of acetaminophen with codeine among NIHB claimants was inversely related to the stringency of provincial regulation.

Acetaminophen↗
PubMed1980

Screening and confirmation of opiates by thin-layer chromatography.

A thin-layer chromatography (TLC) procedure for the screening and confirmation of urinary codeine and morphine has been developed. Urine samples are hydrolyzed to liberate free codeine and morphine, extracted into an organic solvent, and concentrated. For screening, the extraction residues are spotted on TLC plates which are developed in chloroform:ethyl acetate:methanol:propylamine (35:45:5:5). For confirmation, the extraction residues are acetylated and then spotted on TLC plates which are developed in hexane:chloroform:diethylamine (50:30:7). The spots for the two drugs are visualized with acidified iodoplatinate. Codeine and morphine are well separated from one another and from normal urinary substances on both plates and can be detected at a concentration of 0.4 micrograms/mL.

Acetylation↗
PubMed2006

Elenoside increases intestinal motility.

AIM: To study the effects of elenoside, an arylnaph-thalene lignan from Justicia hyssopifolia, on gastro-intestinal motility in vivo and in vitro in rats. METHODS: Routine in vivo experimental assessments were catharsis index, water percentage of boluses, intestinal transit, and codeine antagonism. The groups included were vehicle control (propylene glycol-ethanol-plant oil-tween 80), elenoside (i.p. 25 and 50 mg/kg), cisapride (i.p. 10 mg/kg), and codeine phosphate (intragastric route, 50 mg/kg). In vitro approaches used isolated rat intestinal tissues (duodenum, jejunum, and ileum). The effects of elenoside at concentrations of 3.2 x 10(-4), 6.4 x 10(-4) and 1.2 x 10(-3) mol/L, and cisapride at 10(-6) mol/L were investigated. RESULTS: Elenoside in vivo produced an increase in the catharsis index and water percentage of boluses and in the percentage of distance traveled by a suspension of activated charcoal. Codeine phosphate antagonized the effect of 25 mg/kg of elenoside. In vitro, elenoside in duodenum, jejunum and ileum produced an initial decrease in the contraction force followed by an increase. Elenoside resulted in decreased intestinal frequency in duodenum, jejunum, and ileum. The in vitro and in vivo effects of elenoside were similar to those produced by cisapride. CONCLUSION: Elenoside is a lignan with an action similar to that of purgative and prokinetics drugs. Elenoside, could be an alternative to cisapride in treatment of gastrointestinal diseases as well as a preventive therapy for the undesirable gastrointestinal effects produced by opioids used for mild to moderate pain.

Acanthaceae↗
PubMed2001

Detection of acetylcodeine in urine as an indicator of illicit heroin use: method validation and results of a pilot study.

BACKGROUND: Acetylcodeine (AC), an impurity of illicit heroin synthesis, has been suggested as an interesting biomarker of illicit heroin use. METHODS: Procedures were developed for quantification of (a) morphine, 6-monoacetylmorphine (6-AM), and codeine in urine and (b) diacetylmorphine and AC in urine. Solid-phase extraction of the analytes was performed, and the extracted analytes were analyzed by selected-ion monitoring with gas chromatography-mass spectrometry. This procedure required prior derivatization with propionic anhydride. RESULTS: Different validation parameters were determined, such as linearity, reproducibility, extraction recoveries, and cutoffs. Seventy-one urine specimens of illicit heroin abusers and 44 urine specimens of subjects in a heroin maintenance program were analyzed. AC was detected in 85.9% of the samples of the first group but not in any of the samples from subjects taking medical heroin. In the two groups, there were 94.4% and 84.1% 6-AM positive urine specimens, respectively. Detection times were determined for AC and codeine by parallel administration of heroin containing various percentages of AC to four voluntary patients in a heroin maintenance program. The measured detection times were 8 and 23 h for AC and codeine, respectively. CONCLUSIONS: These results indicate that, together with detection of 6-AM in urine, AC is a suitable marker of illicit heroin use.

Biomarkers↗
PubMed1976

[Mechanism of opiate of oxidative phosphorylation in mitochondria].

Effect of morphine, codeine, dionine and nalorphine on the oxidative phosphorylation in rat liver mitochondria was studied. Morphine is found to inhibit both ATP-synthetase and ATP-ase activities in mitochondria, but not in submitochondrial particles. Morphine-suppressed oxidative phosphorylation was competitively reversed with high concentrations of ADP, but not of inorganic phosphate. The effect of other opiates (i.e. codeine, dionine, nalorphine) was similar. It is suggested, that opiates inhibit the transport of adenine nucleotides through inner mitochondrial membrane, as it does atractyloside. A significance of the hydrophobic interaction between the inhibitor and adenine nucleotide translocase is outlined, since the degree of the inhibition of oxidative phosphorylation is increased with the increase in the number of non-ionized opiate molecules (at alkaline pH values) and in the length of the carbon chain of narcotic molecule as follows: morphine--codeine--dionine--nalorphine.

Adenosine Diphosphate↗
PubMed2003

Paracetamol + tramadol: new preparation. No advance.

(1) First-line treatment for both acute and chronic pain is paracetamol or, if necessary, ibuprofen, a nonsteroidal antiinflammatory drug. If relief is inadequate, the best option is a combination of paracetamol with codeine (a weak opiate). (2) A fixed-dose combination of paracetamol (325 mg) and tramadol (37.5 mg), a weak opiate, arrived on the French market in May 2003. (3) In the acute setting, three trials in a total of 1197 patients showed that a single dose of the paracetamol 650 mg + tramadol 75 mg combination after dental surgery was no more effective than ibuprofen 400 mg. Compared with each drug used alone, the paracetamol + tramadol combination prolongs the analgesic effect but does not increase its intensity. (4) A trial after gynaecological surgery and another trial after orthopaedic surgery showed that a single dose of paracetamol 975 mg + tramadol 112.5 mg had similar efficacy to tramadol alone at 112.5 mg. (5) In the chronic setting, we found no trials comparing the paracetamol + tramadol combination with each drug used alone. A comparative double-blind trial in 462 patients with low back pain or osteoarthritic pain showed no difference in efficacy between paracetamol 325 mg + tramadol 37.5 mg and paracetamol 300 mg + codeine 30 mg. (6) The main adverse effects of the paracetamol + tramadol combination are the same as other weak opiates: nausea, vomiting, dizziness, headache, drowsiness and constipation. Tramadol carries a higher risk of drug interactions than codeine. (7) In practice, the paracetamol + tramadol combination offers patients no advantages relative to standard analgesics.

Acetaminophen↗