PsychoTropical Research - Dr Ken Gillman, Serotonin Syndrome, Mirtazapine, Dual Action Drugs. Antidepressants - Withdrawal symptoms

PsychoTropicalResearch, serotonin and serotonin syndrome research.

Antidepressants - Withdrawal symptoms

Antidepressants - Withdrawal symptoms

Date Created: 22/03/1999   Last Modified: 07/10/2002   Last Checked: 07/10/2002

It seems all antidepressants both old and new, can cause withdrawal symptoms.

Such reactions are most easily distinguished from recurrence of illness symptoms by the fact that they are maximal within about twenty-four to forty eight hours of ceasing (or reducing) medication and diminish thereafter. The return of illness symptoms usually takes some days to emerge, after which they gradually increase.

Known factors which predict a greater severity of withdrawal reactions are:- larger doses, and more rapid rate of decline of drug levels, and duration of treatment more than six weeks.

Rapid rate of decline of drug levels happens with drugs inhibiting there own metabolism (ie showing non-linear pharmacokinetics) such as paroxetine. Other factors being the same drugs with long elimination half lives (eg fluoxetine) will tend to produce less withdrawal symptoms. Fluoxetine and sertraline may be slightly less prone to cause this problem. Paroxetine is probably worse.

Venlafaxine seems to cause particularly severe withdrawal symptoms, with a general feeling of physical unwellness including nausea, headache, fatigue and dizziness. The new extended release formulation may be of some help in relation to this problem but some patients will still have difficulties and substitution of another SSRI may be needed.

Selective serotonin reuptake inhibitor withdrawal reactions include:- dizziness, light-headedness, insomnia, fatigue, anxiety, agitation, nausea, headache and sensory disturbance (including blurring or ‘jerking’ of vision, paresthesias and electric shock or burning sensations).

It seems that many symptoms occur with venlafaxine that are not seen with any selective serotonin reuptake inhibitor (see below) and that is further evidence it may have some other unknown mechanism of action. These are:--

anorexia, confusion, coordination impaired, diarrhea, dysphoric mood, fasciculation, hypomania, nightmares, somnolence, sweating, tremor, vertigo, and vomiting.

FDA:-- amended the product information

Discontinuation symptoms have been systematically evaluated in patients taking venlafaxine.... Abrupt discontinuation or dose reduction... is associated with the appearance of new symptoms, the frequency of which is increased at higher doses and with longer duration of treatment.

Reported symptoms:

agitation, anorexia, anxiety, confusion, coordination impaired, diarrhea, dizziness, dry mouth, dysphoric mood, fasciculation, fatigue, headaches, hypomania, insomnia, nausea, nervousness, nightmares, sensory disturbances (including shock-like electrical sensations), somnolence, sweating, tremor, vertigo, and vomiting.

It is therefore recommended that the dosage of Effexor be tapered gradually and the patient monitored. The period required for tapering may depend on the dose, duration of therapy and the individual patient.