At the far end of the ester scale from propionate sits undecanoate, an eleven-carbon chain and the slowest testosterone ester in general use. Dragon Pharma's Undecanoate 250 is an oil solution carrying 250 mg/ml in a 10 ml vial.
The long chain makes the molecule strongly lipophilic and slow to leave the injection site, which is why preparations of this type are the least frequently administered of the injectable testosterones. The trade-off is viscosity - undecanoate oils are thick, and the high concentration in this vial adds to it.
