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Created February 24, 2021, last updated about 3 years ago.
Collection: 143, Score: 874, Trend score: 0, Read count: 992, Articles count: 3, Created: 2021-02-24 23:40:10 UTC. Updated: 2021-02-25 00:05:08 UTC.Notes
Pethidine (Meperidine) is a phenylpiperidine synthetic opioid first synthesized in 1938. Although widely used in the 20th century, it has fallen out of favour over the past decade due to abuse potential, limited advantages over other opioids and the existence of toxic metabolites.
A. Physiochemistry
- pKa - 8.5 (9% nonionised @ 7.4)
- Octanol water coefficient - 39 (so 40x lipid solubility of morphine)
- phenylpiperidine opioid
B. Pharmacokinetics
- Dose - 25-100 mg (10% morphine potency). Limit 1000 mg 1st day, then 600 mg/day there after.
- Absorption - IV, IM, epidural, po (55% biov)
- Distribution - Vdss 4.5 L/kg. Crosses placenta - foetal 80% of maternal.
- Protein binding - 60%
- Onset 10 min ; Offset 2-3 h
- Metabolism - ß½ 3 h; N-demethylation to norpethidine and then hydrolysis to norpethidinic acid; also direct hydrolysis to pethidinic acid. Renal elimination.
- Norpethidine - ß½ 15 h; 50% analgesic properties, 2x convulsant effects.
- Clearance - 20 mL/kg/min (same as morph & fentanyl)
C. Pharmacodynamics
- Mech - mu and kappa agonist, causing potent spinal and supraspinal analgesia.
- CNS - more euphoria, less N/V than morphine. No miosis, but may cause mydriasis (pupil dilation -atropine-like kappa action). No EEG changes like morphine. ⇡ latency & amplitude of SSEPs.
- NB: has LA action, so can be used as sole agent for neuroaxial block.
- anti-shivering effect (kappa)
- CVS - ⇣ MAP (> than morphine) due to histamine release & alpha adrenergic blockade (vasodilation). Inc HR (atropine like effect). Large doses depress myocardial contractility. May cause hypertensive crisis in those on MAOIs.
- vasodilation
- tachycardia
- depress myocardial contractility
- Resp - potent resp depressant - greater effect on TV than RR. Histamine release. Chest wall rigidity.
Daniel Jolley
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Collected Articles
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Acta Anaesthesiol Scand · Mar 2000
Randomized Controlled Trial Comparative Study Clinical TrialComparison between pentazocine, pethidine and placebo in the treatment of post-anesthetic shivering.
We have compared the effects of pethidine, pentazocine and placebo in the treatment of post-anesthetic shivering. ⋯ We conclude that pentazocine 7.5 mg was not effective in the treatment of post-anesthetic shivering.
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Randomized Controlled Trial Comparative Study Clinical Trial
Self-administered intravenous and intramuscular pethidine. A controlled trial in labour.
In a randomised controlled trial of mothers in labour intramuscular pethidine 150 mg, repeated if necessary, was compared with self-administered intravenous pethidine (0.25 mg/kg available at 10-min-intervals). Each mother agreed to have either method of pain relief and could opt for epidural block. ⋯ There were no differences in mean Apgar scores between the babies in the groups. In mothers who do not choose epidural block, similar pain relief is afforded by adequate intramuscular pethidine or self-demand intravenous pethidine; however, intravenous self-administration is more efficient since the pain relief is achieved with a lower dose of pethidine.
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Randomized Controlled Trial Comparative Study Clinical Trial
Intrathecal meperidine for elective caesarean section: a comparison with lidocaine.
The purpose of this study was to determine the efficacy of intrathecal meperidine in patients undergoing Caesarean section, and also to compare meperidine with heavy lidocaine. Fifty full-term pregnant women, ASA physical status I or II, presenting for elective Caesarean section under spinal anaesthesia were randomly divided into two groups with 25 in each, to receive either intrathecal meperidine or lidocaine. All patients received premedication with oral ranitidine, 150 mg, the night before surgery, and again two hours before surgery. ⋯ All the newborns in both groups cried immediately after birth and had an Apgar score > 7. The mean duration of postoperative analgesia was six hours in the meperidine group and one hour in the lidocaine group (P < 0.01). Postoperative analgesia requirement was less in the meperidine than in the lidocaine group (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)