Through which route should heparin not be administered?

Heparin is an anticoagulant that is primarily used to prevent and treat blood clots. Its administration routes significantly influence its effectiveness and safety. The intramuscular route is avoided for heparin due to the risk of hematoma formation and delayed absorption, which could lead to unpredictable anticoagulant effects. Since heparin is used to achieve rapid anticoagulation, it's crucial that it be administered through routes that provide immediate and consistent effects.

Subcutaneous and intravenous routes are commonly used for heparin administration. Subcutaneous injections allow for gradual absorption and are typically used for prophylactic dosing, while intravenous administration provides immediate therapeutic effects especially in acute situations. The oral route is not suitable for heparin as it is not effectively absorbed through the gastrointestinal tract, thereby rendering it ineffective when taken orally.

Thus, the intramuscular route is the least appropriate for heparin, making it the correct answer.