What conditions impair the absorption of Intramuscular (IM) medication?

From the Guidelines

Patients with severe muscle wasting, low body fat, or those receiving anticoagulant therapy are at risk of impaired absorption of intramuscular (IM) medication. Specific conditions that can make IM injections challenging include:

• Cachexia (severe weight loss and muscle wasting)
• Advanced HIV/AIDS
• Severe malnutrition
• Some neuromuscular disorders
• Patients receiving anticoagulant therapy, as stated in the guidelines from the American Heart Association 1 In these cases, alternative routes of administration should be considered, such as:

• Oral medication (if available)
• Subcutaneous injection
• Intravenous administration For patients with minimal muscle mass, smaller injection volumes (≤1 mL) and smaller gauge needles (23-25G) may be used if IM route is still necessary. Common IM injection sites like the deltoid or vastus lateralis may need to be reassessed, and alternative sites like the ventrogluteal area might be more suitable. According to recent evidence, the use of short needles (e.g., 4-mm pen needles) is effective and well tolerated when compared with longer needles, including a study performed in adults with obesity 1. Healthcare providers should assess the patient's muscle mass and overall physical condition before administering IM medications. In cases where IM injections are difficult, consulting with a pharmacist or specialist can help determine the best alternative method of drug delivery to ensure proper absorption and therapeutic effect.

From the Research

Conditions Impairing Absorption of Intramuscular (IM) Medication

• Muscle mass loss can impair the absorption of IM medication, as it can affect the distribution and metabolism of the drug 2
• Sarcopenia, a condition characterized by the loss of skeletal muscle mass and strength, can also impact the absorption of IM medication 3
• Other factors that can influence the absorption of IM medication include:
  • Age-associated reduction in muscle mass and strength 2
  • Anabolic resistance and protein undernutrition 2
  • Pro-catabolic/anti-anabolic milieu induced by aging and critical illness 2
  • Presence of underlying medical conditions, such as cardiovascular disease, respiratory disease, and diabetes 4
• Additionally, factors such as older age and prefrailty may influence the selection of appropriate candidates for therapies that can affect muscle mass, including GLP-1-based therapies 5
• Low muscle mass, strength, and physical performance have been associated with dependence in activities of daily living (ADL) and instrumental activities of daily living (IADL) in older populations, which can also impact the absorption of IM medication 6