considerations when choosing an antidepressant to switch to

Last edited 02/2023 and last reviewed 02/2023

Considerations when choosing an antidepressant to switch to

• 1) establish the need for an antidepressant switch prior to choosing what to switch to
• 2) consider potential side effects
  • if any previous side-effects were a class effect, switching to a medicine in the same class may not be appropriate
• 3) consider potential interactions
  • potential interactions will depend on the patient's other medicines and the antidepressants involved in the switch
    • some antidepressants can interact in dangerous ways with existing medicines and therefore can't be used, or you may need to avoid cross-tapering antidepressants
    • pharmacodynamic interactions may include serotonin syndrome, hypotension and drowsiness
    • pharmacokinetic interactions may, for example, include elevation of tricyclic plasma levels by some selective serotonin reuptake inhibitors (SSRIs)
• 4) consider a patient's previous response
  • check the person’s treatment history to identify their response to previous treatment and the antidepressant type
• 5) consider a patient's individual characteristics in considering an antidepressant to switch to
  • risks of harm
    • where self-harm or overdose may be a factor, consider the risks of any new medicines on these aspects
  • co-morbidities and age
    • consider existing co-morbidities and the person's age
      • for example, previous or current epilepsy or cardiovascular disease may affect the choice of treatment
      • an older patient may be more susceptible to the additive effects of antidepressants
• 6) consider pregnancy and breastfeeding
  • for women of childbearing potential, consider the choice of antidepressant that's appropriate now and in the future
  • the NHS Specialist Pharmacy Service our articles on the treatment of depression during pregnancy; and the use of SSRIs during breastfeeding and tricyclics during breastfeeding provide summary guidance
• 7) consider the individual needs of the patient
  • a number of other characteristics of the person need to be considered prior to choosing; these include:
    • the person's beliefs
      • consider the person's preference for treatment, perception of risks, benefits, and their expectations
    • the potential for serotonin syndrome
      • serotonin syndrome is an uncommon but potentially serious side effect of most antidepressants
        • characteristic symptoms include: confusion, agitation, hyperreflexia, myoclonus, shivering, sweating, tremor, fever, diarrhoea and inco-ordination
      • concomitant or sequential use of antidepressants can increase the risk of serotonin syndrome as most antidepressants increase serotonin levels in the brain
      • serotonin syndrome is more likely in people taking antidepressants who are:
        • taking a dose of a serotonergic antidepressant towards the top of the licensed dose e.g.  selective serotonin reuptake inhibitors (SSRIs), serotonin and noradrenaline reuptake inhibitors (SNRIs), tricyclic antidepressants and monoamine oxidase inhibitors (MAOIs)
        • taking other serotonergic medicines e.g. pethidine, tramadol, fentanyl, ondansetron, metoclopramide and lithium
        • switching from one serotonergic antidepressant to another
• 8) consider the potential for discontinuation symptom
  • people may experience discontinuation/withdrawal symptoms from abruptly stopping their antidepressant treatment
    • possible discontinuation/withdrawal symptoms include:
      • restlessness
      • trouble sleeping
      • unsteadiness
      • sweating
      • stomach problems
      • feeling as if there's an electric shock in your head
      • feeling irritable, anxious or confused
    • withdrawal symptoms usually come on within 5 days of stopping the medicine and generally last 1 to 2 weeks. Some people have severe withdrawal symptoms that last for several months or more
    • discontinuation symptoms are more likely in people who have or are on:
      • antidepressant treatment for eight weeks or more
      • an antidepressant dose towards the top of the licensed dose
      • an antidepressant with a short half-life (e.g paroxetine or venlafaxine). The half-life can be found in the summary of product characteristics of the antidepressant.
      • other centrally acting medicines such as certain antihypertensives, antihistamines and antipsychotics
      • experienced symptoms of anxiety at the initiation of antidepressant treatment
      • experienced discontinuation symptoms before
• 9) identify complex switches
  • some switches may be particularly high risk and both the choice of medicines to switch to, and the switch itself, should be undertaken with the advice of a mental health specialist. They include switches:
    • for any person under 18 years old
    • to or from an MAOI
    • to or from reboxetine
    • for people who are already on two or more antidepressants
    • for people who have or are suspected of having bipolar disorder
    • for people with chronic depressive symptoms or more severe depression affecting their personal and social functioning and that has not responded to treatment in primary care
    • for people who have coexisting psychosocial and/or physical health risk factors:
      • risk factors for depression include:
        • female sex
        • older age
        • past history of depression
        • personal, social, or environmental factors, such as relationship issues or breakdown, bereavement, stress, poverty, unemployment, homelessness, social isolation, or past history of child maltreatment
        • postpartum period
        • past history of depression
        • family history of depressive illness (first-degree relatives of a person with a 'major' depressive episode have a three-fold increased risk of depression) or suicide
        • history of other mental health conditions and/or substance misuse
        • other chronic physical health conditions associated with functional impairment (such as diabetes mellitus, chronic obstructive pulmonary disease, cardiovascular disease, chronic pain syndromes, epilepsy, stroke disease)
      • risk factors for relapse of depression include:
        • older age of onset
        • history of recurrent episodes of depression, particularly if frequent or within the past two years
        • incomplete response to previous treatment, including residual symptoms
        • unhelpful coping styles or behaviours, such as avoidance or rumination
        • history of severe depression (including severe functional impairment)
        • other chronic physical or mental health conditions, especially in the elderly
        • ongoing personal, social, or environmental factors (see above)
      • when referring to a specialist, ensure the person and/or the carer understand the next steps in receiving care
• 10) planning the switch and monitoring
  • after you've established that a switch is necessary and agreed what you’re switching to, you should plan and agree the strategy and monitor as necessary. You need to:
    • plan and agree an antidepressant switching strategy
      • where the need for an antidepressant switch is established and you've agreed with the individual what to switch to, you can then plan and implement the switch
    • monitor a person during and after switching of an antidepressant
      • review people at appropriate time points; advise on what to expect and report; and beware of the possibility of discontinuation and serotonin syndromes

Reference:

• NHS Specialist Pharmacy Service (February 2023). Choosing an antidepressant to switch a person to