SSRIs to tricyclic antidepressants (TCAs) other than clomipramine
Switching to dosulepin requires specialist advice and should not be done in primary care due to the increased cardiac risk and toxicity in overdose.
From all except fluoxetine, fluvoxamine and paroxetine
Cross-taper
- cross-tapering, starting with a low dose TCA can generaly be undertaken cautiously over 2 to 4 weeks, the speed is determined by individual tolerability
From fluoxetine
Taper, washout and switch
- gradually reduce the dose of fluoxetine to 20mg daily and stop; wait 4 to 7 days before starting low dose TCA
- clinicians should decide the duration of the washout period on a case-by-case basis
If switching from fluoxetine, caution is required as it is a potent inhibitor of the liver enzyme CYP2D6 which is involved in the metabolism of TCAs. There is therefore a risk of raised TCA levels in the body when switching.
Fluoxetine may still cause medicine interactions 5 or 6 weeks after stopping, as fluoxetine and its active metabolite have a long half-life.
From fluvoxamine
Cross-taper
- cross-tapering, starting with a low dose TCA can generally be undertaken cautiously over 2 to 4 weeks, the speed is determined by individual tolerability. It could include:
- gradually reducing the dose of fluvoxamine
- then adding the low dose TCA
- then stopping fluvoxamine after 4 to 7 days. Clinicians should decide the duration of the washout period on a case-by-case basis.
Taper, washout and switch
- alternatively, gradually reduce the dose of fluvoxamine and stop; wait for a period before starting low dose TCA
- clinicians should decide the duration of the washout period on a case-by-case basis
Additional caution
- if switching from fluvoxamine, caution is required because it is a potent inhibitor of the liver enzyme CYP1A2 which is involved in the metabolism of TCAs.
- there is therefore a risk of raised TCA levels in the body when they are administered together
From paroxetine
Cross-taper
- cross-tapering, starting with a low dose TCA can generally be undertaken cautiously over 2 to 4 weeks, the speed is determined by individual tolerability. It could include:
- gradually reducing the dose of paroxetine to 10mg daily
- then adding the low dose TCA
- then stopping paroxetine after 4 to 7 days. Clinicians should decide the duration of the washout period on a case-by-case basis.
Taper, washout and switch
- alternatively, gradually reduce the dose of paroxetine and stop; wait for a period before starting low dose TCA
- clinicians should decide the duration of the washout period on a case-by-case basis
Additional caution
- if switching from paroxetine, caution is required because it is a potent inhibitor of the liver enzyme CYP2D6 which is involved in the metabolism of TCAs
- there is therefore a risk of raised TCA levels in the body when they are administered together
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