Nuzak contains fluoxetine 20 mg, an SSRI antidepressant. It is prescribed for depression, obsessive-compulsive disorder, bulimia nervosa and some anxiety conditions. It takes several weeks to work, and it should not be started or stopped without medical guidance.
What is Nuzak?
Nuzak contains fluoxetine 20 mg in capsule form and is Schedule 5 in South Africa — prescription-only.
Fluoxetine is a selective serotonin reuptake inhibitor (SSRI), the first of its class and still among the most widely prescribed. Nerve cells communicate by releasing serotonin into the gap between them, then reabsorbing it. Fluoxetine blocks that reabsorption, so serotonin remains available for longer.
That is the mechanism, but it is not the full explanation. Serotonin levels rise within hours, yet the benefit takes weeks — so the improvement clearly comes from slower adaptive changes in how nerve circuits function, not simply from more serotonin. This matters practically: judging the medicine after a few days is judging it before it has done anything.
Fluoxetine’s long duration is its distinguishing feature. It and its active breakdown product persist far longer than other SSRIs — days rather than hours. Two consequences follow:
- Missing a single dose matters less than with shorter-acting antidepressants.
- Discontinuation symptoms are usually milder, because levels fall gradually on their own. This is a genuine advantage over SSRIs such as paroxetine.
The same longevity means it takes longer to clear when switching to another medicine, which your doctor will account for.
What is Nuzak commonly used for?
- Depression — the most common reason, including moderate to severe episodes.
- Obsessive-compulsive disorder (OCD), usually needing higher doses and longer to respond.
- Bulimia nervosa, where fluoxetine is the best-established medicine.
- Panic disorder, with or without agoraphobia.
- Anxiety disorders, including social anxiety.
- Premenstrual dysphoric disorder (PMDD), a severe form of premenstrual symptoms.
Expect a realistic timeline. Sleep and appetite often improve first, within one to two weeks. Mood usually lifts over four to six weeks, sometimes longer. Physical side effects, by contrast, tend to appear in the first days and then settle — so the early experience can feel like all cost and no benefit. That pattern is expected and is not a sign the medicine is wrong.
Once it works, treatment usually continues for at least six months after recovery, because stopping early markedly increases relapse risk.
Medicine is rarely the whole treatment. Psychological therapy works at least as well for many people and better in combination.
How Nuzak fits into this medicine category
| Group | Examples | Typical role |
|---|---|---|
| SSRIs | Fluoxetine (Nuzak), escitalopram, citalopram | First-line for depression and anxiety |
| SNRIs | Venlafaxine, duloxetine | Depression, anxiety; duloxetine also nerve pain |
| Tricyclics | Amitriptyline | Older; nerve pain, sleep, depression |
| Benzodiazepines | Diazepam | Short-term anxiety only |
| Antipsychotics | Risperidone | Psychosis, bipolar; sometimes added |
| Anti-epileptics | Carbamazepine, valproate | Mood stabilisation, seizures |
SSRIs are generally first choice because they are effective and safer in overdose than older antidepressants. See the mental health, nerve and neurological medicines hub.
What to check before using Nuzak
Do not stop it abruptly, even though fluoxetine is the most forgiving SSRI in this respect. Any change should be planned with your doctor.
Tell your doctor about every medicine and supplement you take, including over-the-counter products. SSRIs have significant interactions.
Tell your doctor or pharmacist if you:
- Have bipolar disorder, or have ever had a manic episode. An antidepressant alone can trigger mania.
- Have epilepsy.
- Have liver or kidney disease.
- Have diabetes, as blood sugar control may shift.
- Have glaucoma, or a bleeding disorder.
- Have heart problems, or a rhythm disorder.
- Are pregnant, planning pregnancy or breastfeeding. Depression in pregnancy also carries risks, so this is a balance to discuss rather than an automatic reason to stop.
- Are under 25. Antidepressants carry a small increased risk of suicidal thoughts early in treatment in younger people, which warrants closer monitoring rather than avoidance.
- Take tramadol, triptans for migraine, linezolid, St John’s wort, or another antidepressant — all raise serotonin and risk serotonin syndrome.
- Take an MAOI antidepressant. This combination must be avoided, and a gap is needed when switching.
- Take warfarin, aspirin or an anti-inflammatory such as ibuprofen. SSRIs increase bleeding risk, particularly in the stomach.
- Take tamoxifen, where fluoxetine can reduce its effectiveness.
- Take medicines affecting heart rhythm, or lithium.
Alcohol can worsen depression and add to drowsiness. Discuss it with your doctor.
Possible cautions and when to ask a pharmacist or doctor
Common effects, mostly early and often settling within two weeks, are nausea, headache, difficulty sleeping, anxiety or restlessness, reduced appetite, dry mouth, sweating, diarrhoea and tiredness.
Sexual side effects are common and often under-discussed — reduced desire, difficulty reaching orgasm, or erectile difficulty. They affect a substantial minority, and they do not always settle. Raise it if it happens. Dose adjustment or a different antidepressant can often help, and it is a frequent reason people quietly stop taking medicine that is otherwise working.
Seek medical attention urgently if you or those around you notice:
- New or worsening thoughts of suicide or self-harm, or marked agitation or restlessness — especially in the first weeks or after a dose change. This needs same-day attention.
- Agitation, confusion, fever, sweating, shivering, muscle twitching, a racing heart or diarrhoea — possible serotonin syndrome, particularly with another serotonergic medicine.
- A seizure.
- Unusual bruising or bleeding, vomiting blood, or black stools.
- Elevated mood, racing thoughts, reduced need for sleep or unusually impulsive behaviour — possible switch into mania.
- Confusion, marked drowsiness, headache or nausea — possible low sodium, more likely in older people.
- A rash, swelling of the face or lips, or difficulty breathing.
- A fast or irregular heartbeat, or fainting.
Tell your doctor if there is no improvement after four to six weeks, if side effects are limiting, or if your circumstances change. Many people need a dose adjustment or a different antidepressant before finding the one that suits them — needing a second try is common and is not a failure.
Related medicine guides
- Browse Mental Health, Nerve & Neurological Medicines guides
- Read: Trepiline used for
- Read: Nurika used for
Frequently asked questions
What are Nuzak capsules used for? Depression, obsessive-compulsive disorder, bulimia nervosa, panic disorder and some anxiety conditions. Each capsule contains fluoxetine 20 mg.
What is Nuzak 20 mg used for? 20 mg is the standard strength and a common effective dose for depression. OCD often needs more; your doctor decides.
How long does it take to work? Sleep and appetite may improve in one to two weeks; mood usually lifts over four to six weeks. Side effects often appear first and then settle.
Is Nuzak addictive? No. SSRIs do not cause craving or dose escalation. Stopping can cause discontinuation symptoms, which is different from addiction — and fluoxetine causes fewer of these than most.
Can I stop when I feel better? Not on your own. Treatment usually continues for at least six months after recovery, since stopping early raises relapse risk considerably.
Will it change my personality? It should not. The aim is to return you to yourself. Feeling emotionally flattened or numb is a recognised effect worth reporting — it can often be addressed.
Can I drink alcohol on it? Alcohol can worsen depression and add to drowsiness. Discuss it with your doctor.
Does it cause weight gain? Fluoxetine often reduces appetite initially. Longer-term weight changes vary between people — mention it if it becomes a concern.