Vigabatrin powder sachets: how to mix each dose

Short answer: each vigabatrin sachet holds 500 mg of powder. You empty the whole packet into a clean cup, dissolve it in 10 mL of cold or room-temperature water, check that it is clear, draw up the prescribed dose, give it right away and throw the rest away.¹ That gives a solution of 50 mg per mL, and it is made fresh for every dose, twice a day.^1,2

The powder contains the same medicine as the tablets and the ready-to-use liquid. The difference is the mixing step. For how the forms compare, see liquid vs powder.

What is in the box

• Strength: 500 mg of vigabatrin in each packet.¹
• Pack size: 50 packets per carton. Sabril and Vigadrone powders are packed the same way.^1,2
• Storage: room temperature, 20 to 25 °C.¹
• Syringes: not in the box. The pharmacy supplies 3 mL or 10 mL oral syringes separately.¹
• Labeled uses: infantile spasms in babies 1 month to 2 years old, and refractory complex partial seizures from age 2 as an add-on treatment.¹

Several companies make the powder. See brands for the full list.

How to mix vigabatrin powder, step by step

These steps follow the FDA label. The same steps apply to generic powders such as Vigadrone.^1,2

1. Work out how many packets the dose needs (see the table below).
2. Empty the entire contents of each packet into a clean cup.
3. Add 10 mL of cold or room-temperature water for each packet.
4. Let the powder dissolve completely. The solution is now 50 mg per mL.
5. Look at it. If the solution is not clear, throw it away and start again.
6. Draw up the prescribed number of mL with the oral syringe.
7. Give the dose right away.
8. Throw away whatever is left in the cup.¹

From the Sabril powder label, Table 3.¹

The label asks the prescriber to confirm that caregivers understand how to mix the powder and give the right dose.¹ If you have not been shown, ask the pharmacist to walk through it with you.

Ready-to-use liquid, 100 mg/mL

7.5 mL

Drawn straight from the bottle. Fits in one 10 mL oral syringe.

Mixed powder, 50 mg/mL

15 mL

Two packets dissolved in 20 mL of water; 15 mL is given and 5 mL is thrown away. More than one 10 mL syringe-full.

Scale marks every 1 mL, 0–20 mL. Volumes from the FDA dosing tables for each product. Twice daily.

The discard rule

Under the label, each dose is prepared and used immediately, and any unused portion is discarded.¹ For small doses, most of each packet is thrown away. A 5 kg baby starting at 125 mg twice a day uses a whole 500 mg packet each time and discards 7.5 mL, or 375 mg, of mixed solution.¹

Doses are worked out by weight; the dose calculator shows the label volumes for each form.

Where mixing goes wrong

In a 2025 study, 30 people each made one large dose from Sabril powder and one from a ready-to-use liquid, using written instructions only. Everyone measured volumes of both products equally well. The errors came from mixing the powder: 23 of 30 powder doses were within 10% of the target, and doses ranged from 62% too little to 24% too much.³ The study was small and run by employees of the company that makes the liquid, so read it with that in mind.

General research on giving liquid medicines at home helps explain where things slip:

• Match the syringe to the dose. Parents made fewer errors when the syringe size fit the dose. For a 2 mL dose a 5 mL syringe worked better than a 10 mL one, and for 7.5 mL a 10 mL syringe used once beat a smaller syringe refilled.⁴ A 15 mL powder dose means filling a 10 mL syringe more than once.
• Use an oral syringe, not a cup or spoon. Cups led to many more measuring errors than syringes.^5,6
• Count packets carefully when the dose crosses 500 or 1,000 mg. The packet count and the water both change at those points.¹

Mixing with juice, milk or formula

The labels say water only, and each dose is made and used straight away.^1,2

A 2025 lab study tested Vigadrone powder mixed in water, apple juice, whole milk and infant formula, stored capped in the fridge at 2 to 8 °C. All samples stayed within potency and impurity limits at 24 and 48 hours. The authors worked for the generic powder's makers, and the study measured the drug in the cup, not in a child.⁷ It does not change the label. Ask your pharmacist or prescriber before mixing with anything other than water or keeping mixed doses.

Why people call it vigabatrin syrup

In the US, no vigabatrin product is sold as a syrup. When people say "syrup", they usually mean one of two things:

• Mixed powder: 50 mg per mL, made fresh for each dose.¹
• The ready-to-use liquid (Vigafyde): 100 mg per mL, a clear peppermint-flavored solution in a 150 mL bottle.⁸

The same number of mL gives twice as much medicine from the ready-to-use liquid. If a pharmacy, nurse or family member says "syrup", confirm which product and which strength before measuring.⁸

Handling the powder at home

Vigabatrin is on the NIOSH list of hazardous drugs because of possible harm to pregnancy and development.⁹ The NIOSH and USP handling rules are written for healthcare workers, not for parents at home.^10,11 At home, a calm routine is enough: open packets gently over the cup, wipe up any spills, and wash your hands afterward. If someone in the house is pregnant or planning a pregnancy, ask the pharmacist about handling. See safe handling for more.

When the ready-to-use liquid is an option

For babies with infantile spasms between 1 month and 2 years old, a ready-to-use liquid, Vigafyde, needs no mixing. It is labeled only for that group. Older children and adults with refractory complex partial seizures use the powder or tablets.⁸ Switching changes the number of mL for the same dose, so the prescriber should give you the new volume in writing.⁸ See liquid vs powder and cost.