What is the contraindication for the drug Plexion?

Do you mean Plexion topical.

These are the contraindications for Plexion:

Do not use sodium sulfacetamide-sulfur topical without first talking to your doctor if you have an allergy to sulfa products. You may not be able to use sodium sulfacetamide-sulfur topical, or you may require special monitoring during treatment.

Do not apply sodium sulfacetamide-sulfur topical to large areas of open, broken, burned, or infected skin without first talking to your doctor. Large areas of damaged skin may allow more medicine to be absorbed by the body, possibly resulting in side effects.

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Sodium sulfacetamide-sulfur topical is in the FDA pregnancy category C. This means that it is not known whether sodium sulfacetamide-sulfur topical will be harmful to an unborn baby. Do not use sodium sulfacetamide-sulfur topical without first talking to your doctor if you are pregnant or could become pregnant during treatment. It is not known whether sodium sulfacetamide passes into breast milk. Do not use sodium sulfacetamide-sulfur topical without first talking to your doctor if you are breast-feeding a baby.

http://www.drugs.com/mtm/plexion.html