Posted by Jonathan on June 30, 2000, at 23:50:34
In reply to Switching from Wellbutrin SR to Reboxetine, posted by erik.mx on June 30, 2000, at 13:04:05
Erik,
Ask your doctor how he'd advise you if you planned only to discontinue Wellbutrin, without replacing it with another medication -- If he were your flying instructor, you'd have a right to be told how to land! Depending on the dose you're taking and various factors from your medical history, he will probably recommend tapering down over several days to one tablet (150 or 100 mg) per day before stopping abruptly. Any withdrawal symptoms during this tapering period are probably due to Wellbutrin's action on dopamine reuptake: they would _not_ be alleviated by simultaneously starting reboxetine at a lower than normal dose, because reboxetine is highly selective for noradrenaline reuptake.
Wellbutrin has a short half-life (21 hours: that's why there's an SR version) so it disappears from your system quickly. It's extensively metabolized, with some breakdown products hanging around for longer and strongly inhibiting cytochrome P450 2D6. This means that any other drug that is broken down by CYP2D6 should be started with caution and at a reduced dose after discontinuing Wellbutrin -- see http://www.rxlist.com/rxboard/wellbutrin.pl?read=707 for a suspected example of this drug interaction.
Fortunately, reboxetine is broken down by CYP3A4, not CYP2D6, so no washout period should be needed -- see
TI: Cytochrome P-450-mediated metabolism of the individual enantiomers of the antidepressant agent reboxetine in human liver microsomes
AU: Wienkers_LC, Allievi_C, Hauer_MJ, Wynalda_MA
NA: PHARMACIA & UPJOHN INC,DRUG METAB & DISPOSIT RES,DEPT DRUG METAB,7265-300-313,301 HENRIETTA ST,KALAMAZOO,MI,49007
JN: DRUG METABOLISM AND DISPOSITION, 1999, Vol.27, No.11, pp.1334-1340, IS: 0090-9556The recommended dose is one 4 mg tablet every 12 hours for the first three weeks, after which you may increase the daily dose from 8 to 10 mg if necessary (The tablets are scored and break cleanly into equal halves containing 2 mg each.) However, if you find the initial side-effects troublesome they may be reduced by taking only 2 mg (half a tablet) every 12 hours for the first week or two: reboxetine has an even shorter half-life (13 hours) than Wellbutrin so you do need to take at least two doses per day.
Because few have made this pioneering transition from Wellbutrin to reboxetine before you, I'd be tempted to be cautious and start with 2 mg 24 hours after the last dose of Wellbutrin, followed by the other half tablet 12 hours later and then 4 mg every 12 hours.
I've been on reboxetine for 11 weeks (7 on 10 mg/day), having made the transition from 225 mg/day Effexor XR approximately as described above: I tapered the dose of Effexor down to 37.5 mg/day over three weeks, no washout period, then 4 mg reboxetine every 12 hours starting 24 hours after the last dose of Effexor. The most significant side-effects were mild flu-like symptoms probably due to venlafaxine withdrawal, which were alleviated by taking one more Effexor tablet without interrupting the 4 mg twice daily doses of reboxetine.
It definitely works for me, but rather slowly: it took about a month to start working and I'm still a long way from complete recovery.
It's a good idea to have your intra-ocular pressure checked while taking reboxetine (the test that oculists administer by blowing a puff of air at your eyeball). The risk of glaucoma is very small, but the symptoms don't become noticeable until too late. The URL posted by KarenB (previous message, I hope) contains good up-to-date information on other possible side-effects and contraindications.
Good luck, and please let us know how you find these two interesting antidepressants compare.
Jonathan.
poster:Jonathan
thread:38856
URL: http://www.dr-bob.org/babble/20000630/msgs/38904.html