The short answer
- Paxil (IR): 10, 20, 30, 40 mg tablets; full dose released quickly; scored tablets can be split.
- Paxil CR: 12.5, 25, 37.5 mg; gradual release; don’t split, crush or chew.
- Roughly equivalent: CR 12.5 mg ≈ IR 10 mg, CR 25 mg ≈ IR 20 mg, CR 37.5 mg ≈ IR 30 mg. Switching should be done by your prescriber.
Paxil vs Paxil CR side by side
|
Paxil (immediate release) |
Paxil CR (controlled release) |
| Strengths |
10, 20, 30, 40 mg tablets; oral suspension 10 mg/5 mL |
12.5, 25, 37.5 mg tablets |
| Release |
Dissolves in the stomach |
Enteric coat + matrix: releases over 4–5 hours in the intestine |
| Dosing |
Once daily |
Once daily |
| Splitting |
Scored strengths may be split |
No |
| Main advantage |
Flexible dosing, liquid available, cheaper |
Less nausea in early treatment in trials |
| Availability |
Worldwide (Aropax in Australia, Seroxat in the UK) |
Mainly US and some other markets |
Paroxetine itself is the same molecule in both. The CR tablet’s coating keeps it from dissolving in the stomach, which was intended to reduce the nausea that leads some people to stop SSRIs in the first weeks. In the clinical trials that supported Paxil CR, fewer people stopped treatment because of nausea than with immediate-release paroxetine, though the difference is modest. Pexeva (paroxetine mesylate) and Brisdelle (7.5 mg, for hot flushes) are other paroxetine products.
Why Paxil CR can’t be split
Cutting a CR tablet breaks the enteric coat and the release matrix, so more drug is released sooner, in the stomach: more nausea and a higher peak. If you need a dose between strengths, your prescriber can use IR tablets, the oral liquid, or combine CR strengths. The general rules are in our guide to taking medicines correctly.
Switching between IR and CR
Because the CR strengths were set to give similar blood levels to the IR strengths, prescribers usually switch directly from one to the equivalent of the other. You might notice a difference in timing of side effects for a few days. Don’t switch on your own, and don’t combine both forms.
Stopping paroxetine
Paroxetine has a short half-life, and stopping it suddenly often causes discontinuation symptoms: dizziness, “brain zaps”, irritability, flu-like feelings, vivid dreams and nausea. Reduce gradually with your prescriber, sometimes using the liquid form for small steps at the end. Missing a dose can also trigger these symptoms.
Interactions worth knowing
- Bleeding: paroxetine with ibuprofen, aspirin or blood thinners raises the risk of stomach bleeding; paracetamol is the safer painkiller.
- Serotonin: tramadol, triptans, St John’s wort and other antidepressants.
- Tamoxifen: paroxetine strongly blocks CYP2D6 and can make tamoxifen less effective; usually avoided together.
- Metoprolol, some antipsychotics, atomoxetine: levels rise because of CYP2D6 inhibition.
See our guide to combining medicines for more.
Frequently asked questions
Is Paxil CR stronger than Paxil?
No. The milligram numbers differ, but equivalent strengths give similar effects. CR 25 mg roughly equals IR 20 mg.
Can I cut Paxil 20 mg in half?
Immediate-release Paxil 20 mg tablets are scored in many markets and can be split if your prescriber has advised a 10 mg dose.
When should I take Paxil CR?
Once daily, usually in the morning, with or without food. Swallow it whole with water.
Sources and further reading
CanforaMedicine Guide
