This product usually ships by 2 day air on Monday-Wednesday (holidays excepted). Although it is viable for 2 weeks at room temperature without losing potency, it should be refrigerated upon receipt. It is non-returnable. This product ships with an ice pack but the ice pack will be melted and the Pteridin-4 will be at regular room temperature or a bit warmer depending on your location. Refrigerate on arrival.

Tetrahydrobiopterin (BH4, THB, trade name Kuvan) or sapropterin (INN) is a naturally occurring essential cofactor of the three aromatic amino acid hydroxylase enzymes, used in the degradation of amino acid phenylalanine and in the biosynthesis of the neurotransmitters serotonin (5-hydroxytryptamine, 5-HT), melatonin, dopamine, norepinephrine (noradrenaline),epinephrine (adrenaline), and is a cofactor for the production of nitric oxide (NO) by the nitric oxide synthases.