NAC and glutathione: what they are, how they are linked and when a drip makes sense
NAC (N-acetylcysteine) is the precursor of glutathione, the body's main antioxidant. What each one does, how they differ and when a glutathione IV drip makes sense.
English translation of content medically reviewed in Romanian by Dr. Claudiu Ruscu, intensive care physician (anaesthesia & intensive care)· Romanian text reviewed 27 June 2026
What NAC (N-acetylcysteine) is
NAC, or N-acetylcysteine, is a form of the amino acid cysteine. Its best-known role is as a precursor of glutathione — one of the “building blocks” from which the body makes its own glutathione. NAC has long been used in medicine, including as a mucolytic and in liver support.
Why cysteine in particular matters
Glutathione is a tripeptide: it is built from three amino acids — cysteine, glycine and glutamic acid. Of these, cysteine is the limiting one: glycine and glutamic acid are usually available, whereas the availability of cysteine dictates how much glutathione the cell can make.
This is where NAC comes in. Cysteine as such is unstable and oxidises easily; the acetylated form is more stable and easier to give, and the body deacetylates it to release cysteine. In practice, NAC is a convenient way of supplying the raw material from which the cell makes its own glutathione.
It is not a recently invented wellness molecule. N-acetylcysteine has been used in medicine for decades, in two well-established indications: as a mucolytic and, intravenously, as an antidote in paracetamol poisoning — where the mechanism is precisely restoring the liver's glutathione stores used up by the toxic metabolite. This second use is also the one that gives us the best data on how it behaves when given intravenously.
What glutathione is
Glutathione is the main antioxidant produced naturally by the body, present in every cell. It is involved in neutralising oxidative stress and in supporting liver function. Unlike NAC (a precursor), glutathione is the active molecule, ready to use.NAC vs glutathione — what is the difference
In short:
- NAC = the raw material. Taking NAC gives the body the ingredient from which it synthesises glutathione.
- Glutathione = the finished product. Given directly, it bypasses the synthesis step.
Taken by mouth, glutathione is absorbed variably, because it is partly broken down in the digestive tract. That is why, when the goal is a bioavailable antioxidant supply, many people choose intravenous glutathione, which goes straight into the circulation.
Oral or intravenous: with NAC, the route matters more than you might think
This is the part most articles skip, even though it explains most of the practical difference.
Oral N-acetylcysteine has a low absolute bioavailability — between 4 and 10%, because of substantial first-pass metabolism: the molecule is deacetylated in the intestinal lining and then extensively metabolised in the liver before it reaches the systemic circulation. Studies in critically ill patients have estimated a bioavailability of around 11%, close to that in healthy volunteers.
| Oral NAC | Intravenous NAC | |
|---|---|---|
| Bioavailability | low, 4–10% | complete, bypasses digestion |
| What limits it | intestinal deacetylation and first-pass liver metabolism | the rate of administration |
| Doses | high, repeated daily | dose set per session |
| Setting | at home, unsupervised | medical administration, monitored |
Oral effervescent preparations — Fluimucil is the best known in Romania — have their place and are cheap. What they do not do is deliver large amounts of cysteine into the circulation, precisely because of first-pass loss. When the goal is a substantial supply, the intravenous route changes the equation; when the goal is mucolytic, the oral form is sufficient and appropriate.
Honestly: better bioavailability is a measurable pharmacokinetic fact. It does not automatically mean a greater benefit you can feel. If you are healthy and eat a balanced diet, an extra supply of precursor does not necessarily produce a change you will notice.When a drip makes sense
A glutathione drip (alone or combined with vitamin C) is chosen, in a wellness context, for:
- supporting antioxidant balance during demanding periods
- a fresh, bright-looking complexion
- complementing — not replacing — sleep, hydration and diet
Honestly: a drip does not “flush out toxins” and does not fix an unbalanced lifestyle. The benefit is supportive. See also the guide on what a detox drip can and cannot do.
Safety with intravenous NAC
Worth saying, because it is easy to find online and easy to misread.
Intravenous N-acetylcysteine can cause anaphylactoid reactions — rash, flushing, sometimes bronchospasm. In the literature on treating paracetamol poisoning, these reactions are reported in a significant proportion of patients, with figures that vary widely between studies.
Context, however, changes the interpretation completely. Those protocols give a loading dose of 150 mg/kg over 15 minutes — for an adult, around 10,000 mg in a quarter of an hour, that is more than ten times the dose in a support protocol, given tens of times faster. The reactions depend on dose and rate: in one study, most occurred in the first 15 minutes, and their frequency fell dramatically in the segments given slowly.
What this means in practice: at the doses and rates used in a support protocol, the risk is much lower — but the mechanism is real, and that is exactly why administration is done by medical staff, slowly and under supervision, not as a routine procedure done anywhere.
At SYNERVA
We work with glutathione IV drip protocols (600 mg or 1200 mg, from 250 RON), the NAC IV drip — available in two doses, NAC IV drip 600 mg and NAC Forte IV drip 1200 mg — and vitamin IV drips, given by medical staff under the supervision of Dr. Ruscu Claudiu, intensive care physician (anaesthesia & intensive care). Administration is slow and monitored, for exactly the reasons above. We always start with a short medical assessment — we will tell you honestly when a drip makes sense and when it does not.
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Sources
This article is for information only and does not replace a medical consultation.
Frequently asked questions
- Which is better, NAC or glutathione?
- They are not alternatives but different steps of the same process. NAC is the raw material from which the body synthesises glutathione; glutathione is the finished molecule. Given directly, glutathione bypasses the synthesis step. Which one makes sense depends on the goal and is decided at the assessment.
- Why isn't oral NAC enough?
- It may be enough, depending on the goal. The difference is pharmacokinetic: the oral bioavailability of N-acetylcysteine is 4-10%, because of intestinal deacetylation and first-pass liver metabolism. For a mucolytic effect, the oral form is appropriate and cheap. For a substantial supply into the circulation, the intravenous route changes the equation.
- How long does a NAC drip take?
- 45 minutes for the 600 mg dose and 45-60 minutes for NAC Forte 1200 mg. Administration is deliberately slow, for tolerance.
- Does it have side effects?
- Given intravenously, N-acetylcysteine can cause anaphylactoid reactions. The high figures quoted online come from antidote protocols for paracetamol overdose, where 150 mg/kg is given over 15 minutes — more than ten times as much, much faster. The reactions depend on dose and rate, which is why administration is slow and supervised.
- How much does a NAC drip cost?
- 300 RON for NAC 600 mg and 420 RON for NAC Forte 1200 mg, with the medical assessment included.
More in Guides
- Detox: what it really means and what an IV drip can do
Detox is a word used everywhere — but what can an IV drip do, and what can it NOT do? How the body detoxifies itself, where glutathione and NAC help, and where it is just marketing.
- Cerebrolysin: what it is, how it is given and what the studies actually show
Cerebrolysin is a prescription medicine, not a supplement and not a “memory booster”. What an ampoule contains, its licensed indications, why doses above 10 ml are given only as a diluted infusion, and what the Cochrane reviews found — including the uncomfortable part.
- Cerebrolysin — the leaflet in plain English: dosage, dilution, administration
A medicine's leaflet is written for the doctor, not the patient. We translate the part that matters: what an ampoule contains, which dose is given for which indication, why anything above 10 ml is given only as a diluted infusion, and what must not be mixed into the infusion bag.
- How much a Cerebrolysin infusion costs: what the price includes and what a course costs
At Synerva, a session costs 300 RON and includes the medical consultation, the 10 ml ampoule, the infusion and monitoring. What that means for a 10–20-day course, and what needs settling before you book.
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