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High-potency parenteral B + C vitamins Pregnancy: No adverse effects have been reported at recommended doses when used as clinically indicated. Animal studies are insufficient with respect to reproductive toxicity and the potential risk for humans is unknown; caution should be exercised when prescribing to pregnant women. The label gives no separate lactation or fertility statement.)

Vitamin B substances with ascorbic acid

Brand names: Pabrinex

This is a multivitamin preparation combining several B-group vitamins with ascorbic acid (vitamin C), used to prevent or treat deficiencies of these water-soluble vitamins, for example in malnutrition, malabsorption or alcohol dependence.

Adult dose

Dose: RAPID THERAPY OF SEVERE DEPLETION OR MALABSORPTION of the water-soluble vitamins B and C, particularly in alcoholism, where a severe depletion of thiamine can lead to Wernicke's encephalopathy — adults and elderly: 2 to 3 pairs of 5 mL ampoules (1 pair = ampoule No. 1 + ampoule No. 2), that is 10 mL from Ampoule Number 1 PLUS 10 mL from Ampoule Number 2, or 15 mL from Ampoule Number 1 PLUS 15 mL from Ampoule Number 2, diluted with 50 mL to 100 mL of infusion solution (physiological saline or glucose 5%) and administered over 30 minutes every 8 hours, or at the discretion of the physician. TWO FURTHER LICENSED INDICATIONS in the same §4.2 — psychosis following narcosis or E.C.T., and toxicity from acute infections: 1 pair of 5 mL ampoules (5 mL Ampoule Number 1 PLUS 5 mL Ampoule Number 2) diluted with 50 mL to 100 mL of infusion solution and administered over 30 minutes twice daily for up to 7 days. Haemodialysis: 1 pair of 5 mL ampoules (5 mL from each) diluted with 50 mL to 100 mL of infusion solution and administered over 30 minutes once every two weeks at the end of dialysis.
Route: Intravenous infusion ONLY. §4.2 Method of administration: dilute before use; administer by drip infusion — equal volumes of the contents of ampoules number 1 and 2 added to 50 mL to 100 mL physiological saline or 5% glucose and infused over 30 minutes. §4.4 is explicit: 'This medicine is for injection into a vein only and should not be given by any other route', and care should be taken to ensure the route used (intramuscular or intravenous) is the one intended, as reports of unintentional administration by the wrong route have been received.
Frequency: Every 8 hours for severe depletion / Wernicke's-risk therapy, or at the discretion of the physician; twice daily for up to 7 days for psychosis following narcosis or E.C.T. and for toxicity from acute infections; once every two weeks at the end of dialysis in haemodialysis patients.
Max: 3 pairs of 5 mL ampoules per dose — that is 15 mL from Ampoule Number 1 plus 15 mL from Ampoule Number 2 — which is the top of the '2 to 3 pairs' range the SPC states for rapid therapy of severe vitamin B and C depletion. This ceiling belongs to that indication only; the psychosis/acute-infection and haemodialysis regimens are each 1 pair per dose, and the label caps the psychosis/acute-infection course at 7 days. The label states no separate milligram ceiling for any individual vitamin.
THE DOSE IS EXPRESSED IN AMPOULE PAIRS AND MILLILITRES because that is how the SPC expresses it — this is a two-ampoule product in which equal volumes of ampoule No. 1 and ampoule No. 2 are combined before dilution. No milligram figure for any individual vitamin appears in the fetched §4.2, so none has been asserted. || INFUSION TIME IS A SAFETY MEASURE, not just a convenience: §4.4 states that to minimise the risk of serious allergic events this medicinal product should be administered by infusion over a period of 30 minutes. || §4.4 also states that although potentially serious allergic reactions such as anaphylactic shock may occur rarely during or shortly after parenteral administration, that rare occurrence should not preclude use in patients who need treatment by this route, particularly those at risk of Wernicke's encephalopathy, for whom treatment with parenteral thiamine is essential. || §4.5: the pyridoxine content may interfere with the effects of concurrent levodopa therapy. || The 'adult dose' referred to by the paediatric fractions below is the adult regimen for the same indication.

Paediatric dose

Dose: The SPC states this product is rarely indicated for administration to children, but gives its own suitable doses as fractions of the adult dose for the same indication: under 6 years — a quarter of the adult dose; 6-10 years — a third of the adult dose; 10-14 years — half to two thirds of the adult dose; 14 years and over — as for the adult dose.
Route: Intravenous infusion only, diluted with 50 mL to 100 mL physiological saline or 5% glucose and given over 30 minutes
Frequency: As for the corresponding adult regimen for the indication being treated
THESE ARE THE LABEL'S OWN PAEDIATRIC FIGURES, quoted verbatim from the §4.2 'Paediatric population' table — they are fractions of the adult dose set by the manufacturer, not a scaling performed here. §4.2 verbatim: 'Vitamin B&C Intravenous High Potency, Concentrate for Solution for Infusion is rarely indicated for administration to children; however, suitable doses are as follows: Under 6 years quarter of the adult dose; 6 - 10 years third of the adult dose; 10 - 14 years half to two thirds of the adult dose; 14 years and over as for the adult dose.' No mg/kg figure exists anywhere in this label, so dosePerKg is deliberately NOT populated — the dose is a fraction of an adult volume, not a per-kilogram figure, and storing it as one would be wrong. concentration is likewise not populated because the label gives no single mg/mL value for this two-ampoule product. Verify paediatric use against a children's formulary.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to the active substances or to any of the excipients listed in section 6.1
  • PROVENANCE: §4.3 of the Pabrinex / Vitamin B&C Intravenous High Potency SPC, complete in the bundle — the label lists only this one contraindication.

Side effects

  • Frequency unknown: hypersensitivity, including anaphylaxis, rash and urticaria
  • Frequency unknown: paraesthesia
  • Frequency unknown: hypotension
  • Frequency unknown: injection site reactions, including pain and swelling
  • Potentially serious allergic adverse reactions such as anaphylactic shock may occur rarely during, or shortly after, parenteral administration (§4.4)
  • Every tabulated reaction carries the frequency 'unknown' because post-marketing reports come from a population of unknown exposure.

Monitoring

  • Facilities for treating anaphylactic reactions should be available whenever this product is administered
  • Watch for the initial warning signs of a reaction — sneezing or mild asthma; administering further injections to such a patient may give rise to anaphylactic shock
  • Infuse over a period of 30 minutes — this is stated as the measure that minimises the risk of serious allergic events
  • Confirm the intended route before giving: this medicine is for injection into a vein only and must not be given by any other route; unintentional administration by the wrong route has been reported
  • Visually inspect each ampoule before administration, in common with all parenteral products, and do not use if particulates are present
  • Concurrent levodopa therapy — the pyridoxine content may interfere with its effects (§4.5)

Clinical monograph

How it works

The constituent B vitamins act as cofactors in energy and amino-acid metabolism while ascorbic acid supports collagen synthesis and antioxidant defence, so the combination corrects multiple coexisting water-soluble vitamin deficiencies.

Prescribing in practice

  • It is a supportive replacement preparation and should not replace specific high-dose therapy where a particular deficiency such as Wernicke's encephalopathy requires dedicated parenteral thiamine.
  • Confirm the actual dietary or clinical need, as water-soluble vitamins are generally well tolerated but indiscriminate use adds little benefit.
  • Review whether an underlying cause of deficiency, such as poor intake or malabsorption, also needs addressing.

Monitoring

Monitor the clinical response and resolution of deficiency features, and reassess the ongoing need once nutritional status improves.

Counselling the patient

  • These vitamins help correct deficiencies caused by poor diet or absorption.
  • Take as directed and address the underlying cause of any deficiency.
  • Maintain a balanced diet alongside supplementation where possible.

Evidence & guidelines

Water-soluble vitamin replacement is standard supportive care in deficiency and malnutrition, in line with general clinical nutrition practice.

Reference: NICE CG100/NG32; Confirm identity and dosing against the manufacturer SPC (eMC) and NICE. Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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