Drug pump with reinforcing grooves

In an implantable medical device for infusing drugs, medicaments or other liquids into a body, the medical device having a reservoir for the storage of a drug, medicament or other liquid, means operatively coupled to the reservoir for dispensing the drug, medicament or other liquid, an outer shell encasing the reservoir and the means for dispensing the drug, medicament or other liquid, the outer shell having an outside wall, the medical device having an interior, and a propellant chamber defined between the reservoir and the outer shell in which pressurized gas exerts positive pressure against the resevoir, the improvement comprising:

• wherein, the outside wall has at least one depression extending toward the interior from the outside wall, the depression having a depression surface, to reinforce the outer shell particularly against increased pressure in the propellant chamber during heat sterilization.