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Clinician’s Corner: Antidepressants Wrap-up: Switching Methods

We now wrap up the antidepressants by discussion how to switch between the drugs if one drug causes side effects or doesn’t seem to be effective enough.  Your Thompson Pharmacist is a great resource to help your physician to navigate between the therapeutic classes of antidepressants that we have covered the past two months.


Direct switch.

From one SSRI to another SSRI, venlafaxine (Effexor), or duloxetine (Cymbalta).

  • Can switch from paroxetine (Paxil) to sertraline (Zoloft), the next day.
  • Switching from fluoxetine (Prozac) should wait 4 to 7 days because of its long half-life. Then start another SSRI with low dose. Monitor for signs of exacerbation of depression.


Gradually reduce the dose of the old drug while simultaneously increase the dose of the new drug. Use when switching to meds with a different mechanism. Usually takes 1-2 weeks.

  • Such as switching from an SSRI to bupropion (Wellbutrin) or mirtazapine (Remeron).
  • Cross-tapering is also a good idea when switching from paroxetine (Paxil) or venlafaxine (Effexor). Because of short half-life may cause discontinuation symptoms.
  • When cross-tapering, new symptoms can be due to THREE different causes.
      • Discontinuation symptoms from stopping the first drug.
      • Side effects from the new drug.
      • Depression or anxiety symptoms because neither drug is working.

Wash out

A wash-out period is necessary when switching to or from an MAO inhibitor.

Only after a 4 to 8-week trial of an antidepressant, switching is recommended.  For partial responders you can choose between switching OR addition of a second agent.

  • MAOI to tricyclic: wait 2 to 3 weeks between stopping one drug and starting another.
  • SSRI to MAOI: wait 4 to 5 weeks
  • Elderly patients will tolerate a switch to venlafaxine (Effexor) rather than addition of Lithium, bupropion (Wellbutrin) or liothyronine (Cytomel)
  • Within the 3 groups anti-depressant response may be augmented by:   Under psychiatric consult use Lithium or liothyronine (Cytomel  25mcg) (liothyronine-T3).

WEIGHT GAIN on Antidepressants:

Weight gain is problematic antidepressant therapy. As far as side effects sexual dysfunction (17%) and drowsiness (17%) with weight gain being third most common problem at 12%. Weight gain can be attributed to carbohydrate craving and improved appetite as patients experience remission of depression.

Patients gain an average of 6 pounds on mirtazapine (Remeron) or paroxetine (Paxil)

Weight-neutral SSRIs:   suggest fluoxetine (Prozac), sertraline (Zoloft), citalopram (Celexa), or escitalopram (Lexapro).

Weight loss antidepressant: Bupropion (Wellbutrin) is associated with about a 6 lb. weight LOSS


Depression occurs in 14-23% of pregnant women.  OB-Gyn consultation is mandatory.

Key points:

  • ALL SSRI are Pregnancy Category-C except Paxil (paroxetine) Cat-D
  • ALL SNRI are Pregnancy Category-C
  • TCA anticholinergic effects and toxicity in overdose limit usefulness

Are seeing a 2-fold increase in heart defects in babies. 2% (paroxetine exposed) vs 1%

Persistent pulmonary hypertension: increase risk if SSRI used after 20th week.

Poor neonatal adaptation: rapid breathing, hypoglycemia, Irritability, weak/absent cry, and seizures are seen in 15-30% of babies born to Moms taking SSRI in 3rd trimester.

  • Tapering SSRI in 3rd trimester leads to depression before and after delivery.


Cognitive therapy is a must, before conception and during pregnancy. 

  • Fluoxetine (Prozac) well studied, long half-life may cause accumulation. Increased risk of withdrawal symptoms after birth.
  • Stopping pharmacotherapy should be only attempted in women who do not have a history of severe recurrent depression. Do not consider stopping antidepressants if woman is suicidal, other concurrent psychiatric conditions or functional incapacitation.


Your Thompson Pharmacist is a great resource for you or your physician to select the best drug for your mental health needs.  Your pharmacist can also help select the best method to switch from one antidepressant to another.  Go Ahead and ASK… at Thompson Pharmacy, it’s ALL for YOU!!