4-Methadone

Methadone is a synthetic opioid, clinically available in the U.S. since 1947.8 It exists in the dextro- and levo-rotatory forms with the levo-isoform possessing approximately 8 to 50 times more pharmacological activity.27 34 Methadone acts on the CNS and cardiovascular system producing respiratory and circulatory depression. Methadone also produces miosis and increases the tone of smooth muscle in the lower gastrointestinal tract while decreasing the amplitude of contractions. It is used clinically for the treatment of severe pain and in maintenance programs for morphine and heroin addicts.34 

Large individual variations in the urine excretion of methadone are observed depending on urine volume and pH, the dose and rate of metabolism. Acidification of the urine may increase the urinary output of methadone from 5 to 22%.37 Typically, following a 5-mg oral dose, methadone and EDDP account for 5% of the dose in the 24-h urine. In those individuals on maintenance therapy, methadone may account for 5 to 50% of the dose in the 24-h urine and EDDP may account for 3 to 25% of the dose. (S)- and (R)-methadone and EDDP have been reported in saliva38 and methadone and (S)- and (R)-methadone in human breast mi Ik.39 40 

The illicit drugs market deals in methadone just like DHC, but abuse is less often observed than with the three opiates mentioned above [6]. As it is also available without the substances added to prevent parenteral administration, abuse by intravenous application is relatively common. 

---

Phenylpropylamines are another stmctural class of receptor agonist. The two most important members are methadone [76-99-3] C2 H2yNO, (8) (17), discovered in Germany during World War II, and propoxyphene [469-62-5] C22H22NO2, (9). 

A common strategy for treating chronic opiate addiction iavolves the substitution of methadone which can either be provided as maintenance therapy or tapered until abstinence is achieved. Naltrexone and buprenorphine [52485-79-7] have also been used ia this manner. The a2 adrenergic agonist clonidine [4205-90-7] provides some rehef from the symptoms of opiate withdrawal, probably the result of its mimicking the inhibitory effect of opiates on the activity of locus coerukus neurons. 

Methadone hydrochloride (2-dimethylamino-4-ethoxycarbonyl-4,4-diphenylbutane HCl) [W95-90-5J M 345.9, m 241-242 , pKj 8.94, pK 10.12 (free base). Crystd from EtOH. 

The thiophene analog of methadone (253) and isomethadone have been prepared and shown to be active analgesies. Heterocyclic acetamides of the type (254) have been prepared for evaluation of their analgesic and antipyretic activity. - ... 

Synthesis of the intermediate aminonitrile for methadone by (I r giospecific route served to confirm the structure. Alkyla-I Lon of diphenylacetonitrile with l-chloro-2-propanol affords the. ilcohol, 120, free of isomeric products (although it is possible here, too, to imagine cyclization of the halide prior to alkyla-lion). The hydroxyl is then converted to the bromide (121) by... 

Modification of the ketonic side chain is also consistent with retention of analgesic activity. Thus, reduction of methadone with lithium aluminum hydride affords the alcohol, 128 (apparently as a single diastereomer). Acetylation gives acetyl-methadol (129). ... 

Replacement of the ketone by an amide leads to Increased potency. Hydrolysis of nitrile, 133 (obtained by alkylation of diphenylacetonitrile with the morpholine analog of the chloro-amine used in the original preparation of methadone), affords acid, 134. Conversion to the acid chloride followed by reaction with pyrrolidine affords racemoramide (135) Separation of the (+) isomer by optical resolution gives dextromoramide, an analgesic an order of magnitude more potent than methadone. 

Replacement of one of the phenyl groups by an alkyl group of similar bulk, on the other hand, alters the biologic activity in this series. Alkylation of phenylacetonitrile with isopropyl bromide affords the substituted nitrile, 136. Treatment of the anion prepared from 136 with strong base with 2-dimethylamino-l-chloropropane gives isoaminile (137). It is of note that alkylation of this halide, isomeric with that used in the early methadone synthesis, is apparently unaccompanied by isomer formation. Isoaminile is an agent with antitussive activity. 

More radical dissection of the morphine molecule was in progress concurrently with the work above. The chemistry of the series of analgesics that rely on an acyclic skeleton, the compounds related to methadone, is discussed earlier. Suffice it to say that this series of agents, with the possible exception of propoxyphene, seem to share abuse and addiction potential with their polycyclic counterparts. 

Diphenylacetonitrile is condensed with 2dimethyl-amino)-2,2-diphenyl valeronitrile. It is then reacted with ethyl magnesium bromide and then hydrolyzed using HCl to give methadone hydrochloride. 

Oxyphenisatin acetate Diphenylacetic acid chloride Diphenpyramide Thiphenamil HCI Diphenyl acetone Diphenadione Diphenylacetonitrile Doxapram HCI Methadone HCI Diphenylacetyl chloride Piperidolate... 

Azatadine maleate Chlorprothixene Cyproheptadine iphenidol Flupentixol Heptabarbitol Mepivacaine Methadone HCI Methallenestril Methohexital sodium Oxitropium bromide Pipethanate ethobromide Pyrithyidione Ethyl bromoacetate Aceclidine... 

Methadone metabolites, methadone, cocaine (underivatized). morphine, and heroin... 

---