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Effexor (Venlafaxine)
- Generic name: Venlafaxine hydrochloride
- Trade names: Effexor, Effexor XR (Extended Release)
- Pharmacologic category: Serotonin and norepinephrine reuptake inhibitor (SNRI)
- FDA approved: October 20, 1997
- Manufacturer: Wyeth Pharmaceuticals Inc.
- Habit forming? Not known
- Pregnancy risk factor: C
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What is Effexor?
Effexor (Venlafaxine hydrochloride), an antidepressant (mood
elevator) from SNRI class, is indicated for the treatment of depression, generalized
anxiety disorder, social anxiety disorder (social phobia) and
panic disorder. Effexor blocks the ability of the nerve terminals in the
brain to bind and break down serotonin and norepinephrine so that
more is available for the brain to use. Abnormally low levels
of serotonin and norepinephrine may play a role in conditions
such as depression and anxiety disorders.
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Effexor withdrawal
Effexor is associated with a very troublesome discontinuation
syndrome. It happens when people hurriedly stop using Effexor. To avoid severe withdrawal symptoms,
venlafaxine should be tapered step-by-step.
Some people cope reducing the dose by 37.50 mg at
one-week intervals. Other can tolerate tapering by 5 mg every 10 days.
If the discontinuation is terrible, then very slow tapering and cutting the milligrammes at a
rate 5-10% may be the way out. You may need about 3-4 weeks to stabilize after each step down.
Liquid formulation, splitter, and scales may help to measure the right amounts. |
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Pharmacological characteristics
- Absorption: Absolute bioavailability is 45% and well
absorbed (at least 92%). Steady-state concentrations
of venlafaxine and O-desmethylvenlafaxine (ODV) in plasma are
attained within 3 days. Exhibits linear kinetics over dose range 75 to 450 mg/day.
- Metabolism: Extensively metabolized in the liver. The
only major metabolite is O-desmethylvenlafaxine, which is active.
- Elimination half-life: elimination half-life of venlafaxine
is 5 ± 2 and 11 ± 2 hours of O-desmethylvenlafaxine (ODV).
- Excretion: Renal elimination of venlafaxine and its
metabolite is the primary route of excretion. Approximately
87% of a venlafaxine is recovered in the urine within 48
hours as either unchanged venlafaxine (5%), unconjugated ODV
(29%), conjugated ODV (26%), or other minor inactive metabolites (27%).
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Benefits
- powerful antidepressant
- high therapeutic success rate [4]
- often effective for depression not responding to SSRIs [5, 8]
- highest remission rate for depression resistant to other antidepressants [6]
- more effective than other antidepressants for long-lasting remission of depressive symptoms [6]
- rapid onset of action [18]
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Concerns
- high rate of nausea and vomiting
- can increase blood pressure
- high rate of severe withdrawal syndrome [3]
- toxicity in overdose (cardiovascular toxicity, rhabdomyolysis) [19, 20]
- high risk of suicide [1]
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Unlabeled uses
- diabetic neuropathy
- migraine prophylaxis [11]
- hot-flashes
- post-traumatic stress disorder (PTSD) [10]
- fibromyalgia [12]
- tension-type headache [13]
- chronic pain [14]
- polyneuropathy [16]
- premenstrual dysphoric disorder [15]
- attention deficit hyperactivity disorder (ADD/ADHD) [17]
Effexor XR for fibromyalgia
Some studies have shown that Effexor may be effective for fibromyalgia
treatment - though the drug is not approved for this use [12].
Although it is not entirely clear how Effexor works for fibromyalgia,
the drug may help block the nerve pain signals in the spinal cord
or brain. This may help with the pain caused by fibromyalgia.
The studies have shown that Effexor can provide pain relief and
decrease disability due to fibromyalgia. People taking Effexor
for fibromyalgia also showed improvement in anxiety or depression symptoms. |
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Mechanism of action
Effexor (venlafaxine) blocks the reuptake of serotonin, noradrenaline
and, to a lesser extent, dopamine. The drug has the flexibility
of being an SSRI at lower doses and an SNRI at higher doses.
Effexor (Venlafaxine) antinociceptive effects
Effexor (venlafaxine) has an analgesic effect that is independent
of its antidepressant activity. The study has shown that antinociceptive
effect of venlafaxine is mainly influenced by the kappa- and delta-opioid
receptor subtypes combined with the alpha2-adrenergic receptor.
These results suggest a potential use of venlafaxine in some pain syndromes [9]. |
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Ratings, Reviews, Discussions
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Reliable Sources
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References
- 1. Tiihonen J, Lönnqvist J, Wahlbeck K, Klaukka T, Tanskanen A, Haukka J. Antidepressants and the risk of suicide, attempted suicide, and overall mortality in a nationwide cohort. Arch Gen Psychiatry. 2006 Dec;63(12):1358-67. PubMed
- 3. Fava M, Mulroy R, Alpert J, Nierenberg AA, Rosenbaum JF. Emergence of adverse events
following discontinuation of extended-release venlafaxine. Am J Psychiatry. 1997 Dec;154(12):1760-2.
- 4. Einarson TR, Arikian, Casciano J, Doyle JJ. Comparison
of extended-release venlafaxine, selective serotonin reuptake
inhibitors, and tricyclic antidepressants in the treatment of
depression. Clin Ther. 1999 Feb;21(2):296-308.
- 5. Saiz-Ruiz J, Ibanez A, Diaz-Marsa M, Arias F, Padin
J, Martin-Carrasco M, Montes JM, Ferrando L, Carrasco JL, Martin-Ballesteros
E, Jorda L, Chamorro L. Efficacy of venlafaxine in major depression
resistant to selective serotonin reuptake inhibitors. Prog Neuropsychopharmacol
Biol Psychiatry. 2002 Oct;26(6):1129-34.
- 6. Shelton C, Entsuah R, Padmanabhan SK, Vinall PE. Venlafaxine
XR demonstrates higher rates of sustained remission. Int Clin Psychopharmacol.
2005 Jul;20(4):233-8.
- 8. Kaplan EM. Efficacy of venlafaxine in patients with major
depressive disorder who have unsustained or no response to selective
serotonin reuptake inhibitors: an open-label, uncontrolled study.
Clin Ther. 2002 Jul;24(7):1194-200. PubMed
- 9. Schreiber S, Backer MM, Pick CG. The antinociceptive effect
of venlafaxine in mice is mediated through opioid and adrenergic
mechanisms. Neurosci Lett. 1999 Oct 1;273(2):85-8.
- 10. Pae CU, Lim HK, Ajwani N, Lee C, Patkar AA. Extended-release
formulation of venlafaxine in the treatment of post-traumatic
stress disorder. Expert Rev Neurother. 2007 Jun;7(6):603-15.
- 11. Ozyalcin SN, Talu GK, Kiziltan E, Yucel B, Ertas M, Disci R. Venlafaxine in the prophylaxis of
migraine. Headache. 2005 Feb;45(2):144-52. PubMed
- 12. Dwight MM, Arnold LM, O'Brien H, Metzger R, Morris-Park E, Keck PE Jr.
Venlafaxine in fibromyalgia. Psychosomatics. 1998 Jan-Feb;39(1):14-7
- 13. Zissis NP, Harmoussi S, Vlaikidis N, Mitsikostas D, Thomaidis T, Georgiadis G, Karageorgiou K.
A randomized, double-blind, placebo-controlled study of venlafaxine XR in out-patients with tension-type
headache. Cephalalgia. 2007 Apr;27(4):315-24. PubMed
- 14. Taylor K, Rowbotham MC. Venlafaxine hydrochloride and chronic pain. West J Med. 1996 Sep;165(3):147-8.
- 15. Cohen LS, Soares CN, Lyster A, Cassano P, Brandes M, Leblanc GA. Efficacy and tolerability of
venlafaxine in the treatment of premenstrual dysphoric disorder.
J Clin Psychopharmacol. 2004 Oct;24(5):540-3. PubMed
- 16. Sindrup SH, Bach FW, Madsen C, Gram LF, Jensen TS. Venlafaxine versus imipramine in painful polyneuropathy.
Neurology. 2003 Apr 22;60(8):1284-9.
- 17. Mukaddes NM, Abali O. Venlafaxine in children and adolescents
with attention deficit hyperactivity disorder. Psychiatry Clin Neurosci. 2004 Feb;58(1):92-5.
- 18. Andrews JM, Ninan PT, Nemeroff CB. Venlafaxine: a novel
antidepressant that has a dual mechanism of action. Depression. 1996;4(2):48-56.
- 19. Howell C, Wilson AD, Waring WS. Cardiovascular toxicity due to venlafaxine poisoning in adults:
235 consecutive cases. Br J Clin Pharmacol. 2007 Aug;64(2):192-7.
PubMedCentral
- 20. Pascale P, Oddo M, Pacher P, Augsburger M, Liaudet L. Severe rhabdomyolysis following
venlafaxine overdose. Ther Drug Monit. 2005 Oct;27(5):562-4.
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Interesting facts
- Venlafaxine is a representative of a new class of antidepressants
(SNRIs) which inhibit selectively the uptake of serotonin and noradrenaline,
but in contrast to tricyclics, show no affinity for neurotransmitter receptors.
- Effexor XR is a once-daily SNRI approved for the treatment of
depression, generalized anxiety disorder (GAD), and social anxiety
disorder that has been proven effective.
- It was first introduced by Wyeth in 1993. A generic will not
be available to U.S. citizens until 2008.
- Sometimes, Effexor is prescribed "off label" for diabetic
neuropathy in a similar manner to duloxetine.
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