Pharmaceutical Desiccant Packs — USP, GMP Standards and Selection Guide

Why Pharmaceuticals Are Particularly Moisture-Sensitive

Tablets, capsules, powders, and API raw materials all contain chemical bonds susceptible to hydrolysis upon moisture exposure. Accumulated moisture causes three categories of serious degradation:

• Chemical changes: Aspirin hydrolyses to salicylic and acetic acid at RH > 60%; amoxicillin loses up to 20% potency after 30 days at 75% RH / 40 °C.
• Physical changes: Tablets absorb moisture, swell, crumble, or cake; powder formulations clump and lose dose uniformity.
• Microbial growth: Water activity (aw) > 0.6 supports mould growth in botanical extracts and spray-dried powders.

GMP guidelines — WHO Technical Report 908 Annex 9 and US CFR Title 21 Part 211 — require most pharmaceuticals to be stored at ≤ 25 °C / 60% RH (ICH Zone II conditions). Desiccant sachets inside primary packaging are the last line of defence, especially when cold-chain continuity is broken or cargo transits tropical ports.

USP <670> — Testing the Moisture Barrier of Pharmaceutical Containers

USP <670> (Auxiliary Packaging Components) defines methods to evaluate the moisture-protective performance of pharmaceutical packaging materials, including desiccant sachets. Containers are classified as:

• Tight Container: WVTR ≤ 0.5 mg/day/L — HDPE bottles, Type I/II glass with foil seal closure.
• Well-closed Container: WVTR ≤ 2.0 mg/day/L — carton with PE liner.
• Multiple-unit Container: Tested at 40 °C / 75% RH for 336 hours.

Desiccant sachet materials must be non-reactive with the drug substance: PE non-woven, DuPont Tyvek (HDPE spunbond), or food-grade kraft paper. Woven fabric is not acceptable because silica gel beads can escape and contact tablets.

CEMACO Sai Gon supplies non-woven and Tyvek desiccant sachets compliant with USP <670> for primary pharmaceutical packaging. See our full range: CEMACO Sai Gon Silica Gel Catalogue.

FDA 21 CFR §184.1711 and EP 8.0 — Silica Gel Safety for Food and Pharma

In the United States, silica gel is classified as GRAS (Generally Recognized As Safe) by the FDA under 21 CFR §184.1711, permitting indirect contact with food and pharmaceuticals in sealed packaging when used at GMP quantities. In Europe, the European Pharmacopoeia EP 8.0 (section 2.8.1) specifies: SiO₂ purity > 99.5%, 5% aqueous suspension pH 3.5–5.5, heavy metal content < 10 ppm.

Type A silica gel (narrow pore, average diameter 2–3 nm) delivers superior moisture uptake at low RH (< 40%), ideal for bottles requiring internal RH < 30%. Type B (wider pore, 4–6 nm) suits higher-RH environments such as outer cartons.

Selecting 1 g, 2 g, or 3 g Sachets by Bottle Volume

As a general rule, 1 g of Type A silica gel absorbs approximately 0.15–0.20 g of water at 25 °C / 50% RH. The required desiccant capacity depends on the headspace volume inside the container and the WVTR of the bottle material over the intended shelf life.

Bottle volume (mL)	Tablet count	Recommended sachet	Notes
10 – 30	10 – 30	1 g silica gel	Small bottle, minimal headspace. Larger sachet reduces usable volume.
30 – 80	30 – 60	2 g silica gel	Most common for 60-count OTC and nutraceutical bottles.
80 – 200	60 – 120	3 g silica gel	Rx 100-count bottles or bulk nutraceutical jars.
> 200	> 120	2 × 2 g or 1 × 5 g	Distribute evenly in jar. Confirm with in-house QC team.

Frequently Asked Questions

Is pharmaceutical-grade silica gel different from food-grade silica gel?

Chemically they are identical (amorphous SiO₂). The difference lies in documentation and control level: pharmaceutical-grade silica gel requires a COA specifying heavy metals < 10 ppm (per EP 8.0), zero cobalt chloride colourant, and FDA/EP-cleared packaging material. Food-grade HACCP silica gel is sufficient for nutraceuticals, but GMP pharmaceutical plants typically require tighter controls.

Can coloured (blue-to-pink indicating) silica gel be used inside medicine bottles?

Not recommended. Traditional colour indicator uses Cobalt Chloride (CoCl₂), listed as an SVHC (Substance of Very High Concern) under EU REACH. Many EU and Japanese markets have banned or restricted CoCl₂ in food and pharmaceutical packaging. Choose non-indicating white silica gel or methyl-violet indicator as approved by your QA department.

What quantities does CEMACO Sai Gon supply, and is custom branding available?

CEMACO Sai Gon supplies from standard stock quantities upward, with custom printing (logo, product name, batch code) available from MOQ 10,000 sachets per production run. Custom-branded sachets support GMP traceability requirements. Contact us at +84 983 929 232 or Request a Quote.

How should unused silica gel sachets be stored to prevent pre-saturation?

Store in sealed PE drums or foil zip-lock bags in a dry warehouse (RH < 50%, temperature < 30 °C). Apply FIFO (First In, First Out) stock rotation. Sachets that weigh more than 15% above nominal weight should be considered saturated and replaced.

What certification documents does CEMACO Sai Gon provide?

We provide: ISO 9001:2015 certificate, HACCP certificate, Certificate of Analysis (COA) per batch, and Material Safety Data Sheet (MSDS). Additional documents (FDA Letter of Non-Objection, REACH compliance declaration) are available on request for export orders. See our Certification page for full details.