According to the sources provided, the maximum Cosentyx dosage per injection is 300 mg. The recommended dosage for Cosentyx varies depending on the condition being treated. For plaque psoriasis, the recommended starting dose is 300 mg administered as two 150 mg injections at weeks 0, 1, 2, 3, and 4, followed by a maintenance dose of 300 mg every 4 weeks. For psoriatic arthritis, the recommended starting dose is 150 mg administered as two 75 mg injections at weeks 0, 1, 2, 3, and 4, followed by a maintenance dose of 150 mg every 4 weeks. For ankylosing spondylitis, the recommended dosage is 150 mg administered as two 75 mg injections every 4 weeks. It is important to note that the dosage and administration of Cosentyx should be determined by a healthcare professional based on the individual patient's condition and response to treatment.

Sources:
[1] "Cosentyx." DrugPatentWatch, 2021, https://www.drugpatentwatch.com/p/biologics/tradename/COSENTYX.
[2] "Treatment & Dosing." Cosentyx, 2021, https://www.cosentyx.com/plaque-psoriasis/treatment-dosing.
[3] "Cosentyx Dosage." Drugs.com, 2021, https://www.drugs.com/dosage/cosentyx.html.