methadone (Dolophine; Methadone HCl Intensol; Methadose; Methadose Sugar-Free) (cont.)

Pharmacy Author:
Medical and Pharmacy Editor:

The conversion ratio from oral methadone to methadone given as an injection (I.V., SubQ) or I.M.) is 2:1. The total daily amount of methadone that a person is prescribed is not fixed, and it will depend on many factors including the severity of the pain, prior use of methadone, medications that are being taken concomitantly, the response to treatment and other factors that may be specific to a person. Therefore, each person has to be monitored carefully while receiving methadone. When stopping therapy, the dose of methadone should be gradually reduced in order to avoid withdrawal symptoms.

DRUG INTERACTIONS: Methadone when taken with drugs that slow brain function, such as alcohol and barbiturates (phenobarbital), can increase the effects of these drugs. Since methadone causes constipation, taking antidiarrheal medications such as diphenoxylate and atropine (Lomotil) and loperamide (Imodium) along with methadone can result in severe constipation. Drugs that block narcotic (opioid) receptors including pentazocine (Talwin), nalbuphine (Nubain), naloxone (Narcan), butorphanol (Stadol) and buprenorphine (Subutex) can lead to withdrawal symptoms.

Rifampin (Rifadin), barbiturates, carbamazepine (Tegretol), phenytoin (Dilantin), primidone and St. John's wort preparations can increase the liver's ability to metabolize (eliminate) methadone and reduce its blood concentration which could result in withdrawal side effects, while drugs such as erythromycin (E-Mycin, Eryc, Ery-Tab), clarithromycin (Biaxin, Biaxin XL), ketoconazole (Nizoral), and itraconazole (Sporanox) can decrease the liver's ability to metabolize methadone thereby increasing the side effects of this drug.

Medically Reviewed by a Doctor on 4/16/2014


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