Subcutaneous drug delivery: An evolving enterprise.
Jones GB, Collins DS, Harrison MW, Thyagarajapuram NR, Wright JM.
Sci Transl Med. 2017 Aug 30;9(405).
Injection of substances is the most effective way of delivering a drug without degradation by the digestive system (parenteral administration).
This is particularly a problem for proteins, such as the antibodies characteristic of biologic drugs.
Injections can be made subcutaneously or intravenously:
-the latter is faster it needs to be administered in a medical setting and can amount up to half the cost of the treatment.
-As for injections done in the Subcutis (Hypodermis or Adipose tissue)
1. They can be done by the patient himself/herself which saves time and costs.
2. they always make it to the venous system but the route is longer if the molecules are large.
Challenges of Subcutaneous Injections
Size matters !(see figure)
-For molecules less than 20 Kilodaltons such as small molecules and insulin, absorption can be done by capillaries.
-However larger molecules more than 20 kDa, such as monoclonal antibodies (biologics), premature degradation can occur in the interstitial tissue as a longer path through the lymphatic system is required before it finally reaches the subclavian vein.
-How to avoid immunogenic and inflammatory responses at the injection site ?
-Safeguards to avoid overdosing and underdosing
Obtaining a comparable therapeutic benefit than intravenously
-The same bolus administered through the vein cannot be injected subcutaneously (pressure buildup). Aside from this, induration (hardening of tissue), and edemas (tissue swelling) are potential adverse consequences
Reducing pain: last but not least
Example: patients prefer abdominal injection sites, the higher-viscosity formulations are less painful.
In terms of efficacy and mode of administration, the pharmaceutical industry has long understood where the smart cookie lies. Indeed 7 out 10 drugs which top the sales of medication are the so-called biologics.
Article selected by Saurat JH, MD