[Subcutaneous infusion: Indications, practical considerations, and tolerability]

Subcutaneous (SC) infusion, or hypodermoclysis, is a route of administration involving the injection of fluids or medications into the hypodermis. Historically used and subsequently abandoned due to complications arising from poor technique, it has regained interest since the 1990s, particularly in geriatrics and palliative care. Compared with the intravenous (IV) route, it is less invasive, better tolerated, easier to implement in outpatient settings, and carries a lower risk of serious complications. The pharmacokinetics of the SC route show slightly slower absorption than IV administration, with bioavailability often exceeding 80% for hydrosoluble compounds. Main indications include the preventive or therapeutic management of moderate dehydration, palliative care (analgesics, anxiolytics, antipyretics, antisecretory agents), and some antibiotics (such as ceftriaxone, as well as ertapenem and teicoplanin, with a good level of supporting evidence). In internal medicine departments, the SC route can also be used for furosemide, levetiracetam, and vitamin B12 when no alternative is available. Some vaccines may be administered subcutaneously in patients with contraindications to the intramuscular route. Local adverse events may occur but are generally mild (pain, edema), transient, and infections are rare. Although often used off-label, hypodermoclysis is a safe and practical alternative, particularly suited to elderly or frail patients, and meets current healthcare challenges related to outpatient medicine and hospital overcrowding. Its wider adoption relies on healthcare professional training, standardized protocols, and robust comparative data.