MEPERIDINE

Dolosal,Specia,France,1943

Analgesic (narcotic).

ChEBI: Pethidine is a piperidinecarboxylate ester that is piperidine which is substituted by a methyl group at position 1 and by phenyl and ethoxycarbonyl groups at position 4. It is an analgesic which is used for the treatment of moderate to severe pain, including postoperative pain and labour pain. It has a role as an opioid analgesic, a kappa-opioid receptor agonist, a mu-opioid receptor agonist and an antispasmodic drug. It is an ethyl ester, a piperidinecarboxylate ester and a tertiary amino compound. It is a conjugate base of a pethidine(1+).

80 parts of finely pulverized sodium amide are added in portions each of about ? of the entire quantity, while stirring and cooling in a suitable manner, to a mixture of 756 parts of methyl-di(β-chloroethyl)-amine (prepared from di-ethanol-methylamine by means of thionyl chloride), 117 parts of benzyl cyanide and 600 parts of toluene. The reaction sets in at once at room temperature. The temperature is maintained between 30° and 40°C; when self-heating no longer occurs a further portion of the sodium amide is introduced. During the reaction heat is liberated and gaseous ammonia escapes.
The mixture is then slowly heated to the boiling point of toluene and kept boiling for one hour under reflux. After the mixture has been allowed to cool the sodium chloride which precipitates is separated by extraction with water. The solution of toluene is then extracted with dilute hydrochloric acid. From the hydrochloric acid extract the basic substance is separated in the form of an oil by means of caustic soda solution and is introduced into ether. The ethereal solution is dried with the aid of potassium carbonate and then distilled.
Under a pressure of 4.5 ml the 1-methyl-4-phenyl-piperidine-4-carboxylic acid nitrile passes over at a temperature of about 148°C in the form of a colorless oil; under a pressure of 6 ml it passes over at about 158°C. After having been allowed to cool the distillate solidifies completely to form a crystalline mass. Its solidification point is at 53°C; the yield amounts to about 135 parts, that is, about 2/3 of the theoretical yield. When recrystallized from isopropyl alcohol the hydrochloride of the nitrile forms colorless crystals, readily soluble in water and melting at 221° to 222°C.
The nitrile may best be saponified with methyl alcoholic potash while heating to 190° to 200°C with application of pressure. After the methyl alcohol has evaporated the salt is introduced into water and by the addition of dilute mineral acid until the alkaline reaction to phenolphthalein has just disappeared, the amphoteric 1-methyl-4-phenyl-piperidine-4-carboxylic acid is precipitated while hot in the form of a colorless, coarsely crystalline powder. When dried on the water bath the acid still contains 1 mol of crystal water which is lost only at a raised temperature. The acid melts at 299°C. Reaction with ethanol yields the ester melting at 30°C and subsequent reaction with HCl gives the hydrochloride melting at 187° to 188°C.

Demerol (Hospira); Demerol (Sanofi Aventis).

Narcotic analgesic

Meperidine (Demerol) is a phenylpiperidine derivative of morphine that was developed in the late 1930s as a potential anticholinergic agent. It has some anticholinergic side effects that lead to tachycardia, blurred vision, and dry mouth. Meperidine is approximately onefifth as potent as morphine and is absorbed only half as well when administered orally as parenterally. It has a rapid onset and short duration of action (2 hours), that is, approximately one-fourth that of morphine.
Like morphine, meperidine has an active metabolite, normeperidine, formed by N-demethylation of meperidine. Normeperidine is not analgesic but is a proconvulsant and a hallucinogenic agent. For this reason, meperidine use in patients with renal or liver insufficiency is contraindicated because of the decreased clearance of the drug and its metabolite. Convulsant activity has been documented in elderly patients given meperidine and in patients using PCA who have decreased renal function.
Meperidine differs from morphine in that it has far less antitussive effect and little constipative effect. The drug is particularly useful in cancer patients and in pulmonary patients, in whom the cough reflex must remain intact. However, it does have more seizure-inducing activity than morphine. Although meperidine produces spasms of the biliary tract and colon, such spasms are of shorter duration than those produced by morphine.
Meperidine readily passes the placenta into the fetus. However, respiratory depression in the newborn has not been observed, and meperidine clearance in the newborn is rapid in that it does not rely upon conjugation to glucuronides. Meperidine, unlike morphine, has not been associated with prolongation of labor; conversely, it increases uterine contractions.

Meperidine (Demerol) was discovered in 1939 during a serendipitous screening of compounds being studied for antispasmodic activity. Mice given meperidine were noted to carry their tails in an erect position (the Straub tail reaction), which was indicative of narcotic analgesia. This led to the study of meperidine and derivatives as analgesic agents. Meperidine was found to have low potency at the receptor compared with morphine (0.2%) but much higher penetration into the brain resulting in a compound with about 10% of the potency of morphine.
Structural changes that increase the potency of meperidine include the introduction of an mhydroxyl on the phenyl ring, substituting the methyl on the N for a phenylethyl or a p-aminophenylethyl. Replacing the N-methyl with an N-allyl or N-cyclopropylmethyl group does not generate an antagonist, unlike the similar substitution of the morphine congeners. Meperidine quickly penetrates the blood-brain barrier and thus has a quick onset of activity and a high abuse potential.

Contraindications are similar to those of morphine. In addition, because normeperidine accumulates in renal dysfunction and meperidine accumulates in hepatic dysfunction, meperidine is contraindicated in such patients because of convulsant effects. Similarly, the use of meperidine is contraindicated in patients who have a history of seizures or who are taking medication to prevent seizures. Phenytoin administered for seizures may reduce the effectiveness of meperidine by increasing the metabolism of the drug in the liver. Meperidine is not generally used in patients with cardiac dysfunction, since its anticholinergic effects can increase both heart rate and ectopic beats.