WHAT IS THIS MEDICINE AND WHAT IS IT USED FOR?
Seroxat contains paroxetine hydrochloride, one of the most widely
prescribed medicines in the SSRI (selective serotonin reuptake inhibitor)
class. SSRIs work by blocking the reuptake of serotonin — a neurotransmitter
involved in mood, emotion, and anxiety — back into the nerve cell that released
it.
By keeping serotonin available for longer in the synaptic gap between
nerve cells, paroxetine increases serotonergic activity and gradually improves
mood and reduces anxiety.
Paroxetine is licensed for a wide range of conditions: major depressive
disorder (clinical depression); panic disorder (with or without agoraphobia);
obsessive compulsive disorder (OCD); generalised anxiety disorder (GAD); social
anxiety disorder (social phobia); post-traumatic stress disorder (PTSD); and
premenstrual dysphoric disorder (PMDD).
The 30mg tablet is typically used for patients who need a higher dose
within the licensed range — the usual starting dose is 10 to 20mg and the
maximum licensed dose is 50mg (60mg for OCD) for adults.
3. HOW TO TAKE THIS MEDICINE
Always start at a lower dose (typically 20mg) and increase gradually if
needed — the 30mg tablet is for patients already established on treatment who
require dose optimisation. Take once daily — typically in the morning (morning
dosing can reduce sleep disturbance). Take with or without food. Do not stop
suddenly — paroxetine must be tapered slowly when treatment ends (see
warnings). Swallow whole with water.
Paroxetine has one of the highest rates of discontinuation syndrome among
SSRIs — this is a specific pattern of symptoms that can occur when doses are
reduced or missed, particularly with paroxetine. These are not signs of
addiction but of the drug's short half-life causing fluctuating serotonin
levels. Symptoms include dizziness, electric shock sensations ('brain zaps'),
flu-like feelings, anxiety, irritability, nausea, and insomnia. Any dose
reduction should be done very slowly and gradually under medical guidance.
⚠ PATIENT TIP: Never stop paroxetine suddenly —
even missing one or two doses can cause discontinuation symptoms. If you want
to stop taking paroxetine, speak to your doctor first — they will create a
tapering plan (gradually reducing the dose over weeks to months). Do not try to
come off it abruptly, even if you feel well. This is not a sign of dependence —
it is simply how paroxetine's pharmacology works.
4. POSSIBLE SIDE EFFECTS
|
How Common? |
Side Effects |
|
Very Common at Start
(usually improves after 2–4 weeks) |
Nausea, dry mouth,
drowsiness, sweating, sexual dysfunction (reduced libido, difficulty reaching
orgasm, delayed ejaculation), insomnia or drowsiness, diarrhoea or
constipation, increased appetite and weight gain |
|
Common |
Headache, dizziness,
tremor, blurred vision, yawning, jaw clenching (bruxism), agitation, anxiety
increase in first 1–2 weeks |
|
Serious — Tell Your
Doctor |
Suicidal thoughts or
thoughts of self-harm (particularly in young people under 25 in the early
weeks of treatment — seek urgent help if these develop). Serotonin syndrome
(if combined with other serotonergic medicines — see interactions):
agitation, confusion, rapid heart rate, high temperature, muscle rigidity.
Hyponatraemia (low blood sodium — particularly in elderly patients):
headache, confusion, weakness — blood sodium check if these symptoms occur.
Mania or hypomania (in patients with bipolar disorder — paroxetine can
trigger manic episodes). Prolonged erection (priapism) — rare but requires
urgent medical attention. Bone fractures (SSRIs reduce bone density with
long-term use — monitor in post-menopausal women and older adults). Bleeding:
SSRIs reduce platelet aggregation — increased bruising and bleeding risk,
especially with NSAIDs. |
5. WHO SHOULD NOT TAKE THIS MEDICINE
Paroxetine must not be taken with MAO inhibitors (phenelzine,
tranylcypromine, isocarboxazid, moclobemide, rasagiline, selegiline) — a
minimum 14-day washout is required before switching from a MAOI to paroxetine
or vice versa; 5 weeks washout after fluoxetine. It is contraindicated in
patients taking thioridazine (an antipsychotic) or pimozide.
Not recommended during pregnancy — paroxetine is associated with cardiac
defects in the first trimester and neonatal adaptation syndrome if used in the
third trimester. It is not recommended during breastfeeding.
⚠ SUICIDAL THOUGHTS IN YOUNG PEOPLE: All
antidepressants carry a warning about an increased risk of suicidal ideation —
particularly in under-25s — in the early weeks of treatment, before the
therapeutic effect builds. Monitor carefully in the first 2 to 4 weeks. If
suicidal thoughts develop or worsen, seek urgent medical help immediately.
⚠ NEVER STOP SUDDENLY: Paroxetine has a short
half-life and is particularly associated with discontinuation syndrome when
stopped abruptly or missed. Always taper doses very gradually — over weeks to
months depending on duration of treatment. Your doctor will create a specific
tapering plan.
⚠ PREGNANCY: Paroxetine is associated with
cardiac septal defects (heart abnormalities) in babies exposed in the first
trimester, and with neonatal adaptation syndrome (respiratory problems,
irritability, feeding difficulties) if used in the third trimester. If you are
pregnant or planning pregnancy, discuss urgently with your doctor — the risks
and benefits of continuing vs switching must be carefully assessed.
6. MEDICINES THAT INTERACT WITH THIS TREATMENT
MAO inhibitors: absolutely contraindicated (fatal serotonin syndrome
risk) — 14-day washout required. Triptans (sumatriptan, rizatriptan): serotonin
syndrome risk — avoid or use with extreme caution. Tramadol, fentanyl,
pethidine (opioids with serotonergic activity): serotonin syndrome risk.
Linezolid and methylene blue (have MAOI activity): contraindicated.
Tamoxifen: paroxetine strongly inhibits CYP2D6, which converts tamoxifen
to its active metabolite endoxifen — this combination significantly reduces
tamoxifen's effectiveness in breast cancer — avoid in breast cancer patients on
tamoxifen.
NSAIDs and aspirin: increased bleeding risk (additive antiplatelet
effect). Warfarin: increased bleeding risk — monitor INR. Lithium: serotonin
syndrome risk — monitor carefully. Clozapine and risperidone: paroxetine
inhibits CYP2D6 — increased levels of these medicines.
7. HOW TO STORE THIS MEDICINE
Store below 25°C. Keep in original packaging away from moisture. Keep out
of reach of children.
8. PRESCRIPTION REQUIREMENT
|
Field |
Details |
|
Status |
Prescription Only
Medicine (POM) — prescribed by GPs, psychiatrists, or relevant specialists |
9. GUIDANCE FOR PATIENTS & CAREGIVERS
Take one tablet once daily — typically in the morning with or without
food. The full benefits of paroxetine for depression or anxiety take 4 to 6
weeks to develop fully — do not give up in the first few weeks even if you feel
worse initially. If you experience increased anxiety or any suicidal thoughts
in the first 2 to 4 weeks, contact your doctor or mental health team promptly —
do not stop taking it without advice.
Never stop paroxetine suddenly — if you want to stop, always discuss this
with your doctor first and follow a slow tapering plan. If you are being
treated for breast cancer with tamoxifen, tell your oncologist you are taking
paroxetine — this combination significantly reduces tamoxifen's effectiveness
and may need to be changed. Tell every doctor, pharmacist, and dentist that you
take paroxetine before any new medicine is prescribed.
10. PHARMACIST & PRESCRIBER NOTES
|
Field |
Details |
|
Clinical Dispensing
Notes |
Paroxetine 30mg SSRI —
CYP2D6 inhibitor (strong). Critical interaction: tamoxifen — paroxetine
strongly inhibits CYP2D6 conversion of tamoxifen to active endoxifen,
significantly reducing breast cancer treatment efficacy. Avoid in breast
cancer patients on tamoxifen; if antidepressant is needed, use sertraline or
venlafaxine (lower CYP2D6 inhibition). MAO inhibitor interaction: 14-day
washout required (both directions); longer for irreversible MAOIs;
fluoxetine-to-paroxetine switch requires 5-week washout. Discontinuation
syndrome: paroxetine has the highest discontinuation syndrome rate among
SSRIs due to short half-life and potent serotonin reuptake inhibition.
Counsel explicitly: never stop suddenly; any reduction must be very gradual
(weekly reductions of 10mg or less, over weeks to months for long-term
users). Suicidal ideation warning: young patients (<25) — counsel patient
and carer on first 2–4 week monitoring. Hyponatraemia: elderly patients —
sodium monitoring if symptomatic. NSAID/aspirin: increased bleeding risk.
Warfarin: INR monitoring. Lithium: serotonin syndrome monitoring.
Clozapine/risperidone: increased levels via CYP2D6 inhibition — check doses.
Pregnancy: cardiac defect risk T1; neonatal adaptation syndrome T3. |
11. FREQUENTLY ASKED QUESTIONS
Q: Why can't I just stop taking it when I feel better?
Two important reasons. First, stopping too soon increases the risk of
relapse — depression and anxiety are much more likely to return if paroxetine
is stopped before a full course is completed (typically at least 6 months after
recovery). Second, paroxetine has a short half-life and is particularly likely
to cause discontinuation syndrome if stopped abruptly — causing distressing
symptoms like dizziness, 'brain zaps,' flu-like feelings, and anxiety that are
not a sign of addiction but are a pharmacological effect.
Q: I'm feeling more anxious since starting — is that normal?
Yes — a temporary increase in anxiety in the first 1 to 2 weeks is a
common and recognised effect when starting SSRIs, including paroxetine. It
usually settles as the therapeutic effect builds. However, if you develop
thoughts of harming yourself or severe distress in the first few weeks, seek
urgent medical help — do not stop the medicine without speaking to your doctor
first.
Q: Can I take paroxetine during pregnancy?
Paroxetine is associated with a small risk of heart abnormalities in the
baby if taken in the first trimester, and with breathing difficulties and
irritability in newborns if taken close to delivery. If you are pregnant or
planning pregnancy, discuss this urgently with your doctor — the decision
depends on weighing the risks of untreated depression against the risks of
continuing the medicine.
Q: What should I do if I miss a dose?
If you remember the same day, take the missed dose. If it is close to the
time of your next dose, skip it and continue as normal. Do not double up.
Missing one or two doses of paroxetine can cause discontinuation symptoms
(dizziness, brain zaps, nausea) because of its short half-life — these are
unpleasant but not dangerous and resolve quickly once the regular dose is
resumed.