Minoxidil or 2,4-Diamino-6-piperidinopyrimidine 3-oxide is a medication used for the treatment of high blood pressure and pattern hair loss. Minoxidil is an odorless, white to off-white, crystalline powder.

General Properties and Specifications of Minoxidil as per IP:
Appearance: White to off-white crystalline powder.
Odor: Odorless.
Identification:
By IR.
By UV.
By TLC.
Chemical Test.
Heavy metals: 20 ppm maximum.
Loss on drying: 0.5% maximum.
Sulfated ash: 0.1% maximum.
Related substances by HPLC: 1.5% maximum.
Residual solvents:
Methanol: 3000 ppm maximum.
Piperidine: 1000 ppm maximum.
Pyridine: 200 ppm maximum.
N-methyl pyrrolidone: 530 ppm maximum.
Ethylene dichloride: 5 ppm maximum.
Benzene: 2 ppm maximum.
Solubility: Slightly soluble in water. Soluble in methanol and in propylene glycol. Very slightly soluble in ether. Practically insoluble in chloroform and in acetone.
Melting Point: 248C.
Storage: Room temperature. Short term shipping may be ambient.

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Minoxidil USP Grade Specifications:
C9H15N5O --- 209.25
2,4-Pyrimidinediamine, 6-(1-piperidinyl)-, 3-oxide;
2,4-Diamino-6-piperidinopyrimidine 3-oxide CAS 38304-91-5
UNII: 5965120SH1

DEFINITION
Minoxidil contains NLT 97.0% and NMT 103.0% of minoxidil (C9H15N5O), calculated on the dried basis.

IDENTIFICATION
A. Infrared Absorption: Do not dry specimens.

Residue on Ignition: NMT 0.5%
Organic Impurities: NMT 1.5%
Loss on Drying: Dry a sample at 50C and at a pressure not exceeding 5 mm of mercury for 3 h. Acceptance criteria: NMT 0.5%
Packaging and Storage: Preserve in well-closed containers.

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Minoxidil BP Ph Eur Grade Specifications:
C9H15N5O --- 209.3 CAS 38304-91-5
Action and use: Vasodilator; treatment of hypertension; male pattern baldness.

DEFINITION
6-(Piperidin-1-yl)pyrimidine-2,4-diamine 3-oxide.
Content: 99.0 per cent to 101.0 per cent (dried substance).

CHARACTERS
Appearance: White or almost white, crystalline powder.
Solubility: Slightly soluble in water, soluble in methanol and in propylene glycol.

IDENTIFICATION
First identification: B
Second identification: A, C, D
A. Ultraviolet and visible absorption spectrophotometry.
B. Infrared absorption spectrophotometry.
C. Thin-layer chromatography.
D. Dissolve about 10 mg in 1 mL of methanol. Add 0.1 mL of copper sulfate solution. A green colour develops. The solution becomes greenish-yellow on the addition of 0.1 mL of dilute hydrochloric acid.

Related substances: To pass the test by Liquid chromatography.
Loss on drying: Maximum 0.5 per cent, determined on 1.000 g by drying in an oven at 105C.
Sulfated ash: Maximum 0.1 per cent, determined on 1.0 g.

For Original Monographs of IP Indian Pharmacopoeia EP Ph Eur European Pharmacopoeia BP British Pharmacopoeia USP US Pharmacopoeia FCC Food Grade product, please check with the respective web-pages or books.