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Medication Interference

• Undesirable medication interactions must be considered.
• Interactions include illicit drugs, over-the-counter medications, prescribed medications, and herbal remedies.
• Incompatibility during administration or through the same IV tubing pose a major concern.
• Some medications can change the chemical composition or deactivate others, emphasizing the importance of using proper IV solutions.
• Medications can increase, decrease, or alter each other's effects within the body.

Types of Medication Interactions

Altered Absorption

• One medication either increases or decreases the body's ability to absorb another medication.
• Pepcid (H2 blocker) can reduce the absorption of antifungals or certain cephalosporin antibiotics.

Principles of Pharmacokinetics

• The body begins moving and removing the medication as it's administered.
• Dosage, administration route, and patient's clinical status affect medication duration and effectiveness.
• Onset and peak effect relate to absorption and distribution.
• Duration of effect relates to medication metabolism and elimination.
• Decreasing medication near cell receptors leads to decreased effects.
• If a medication permanently binds or irreversibly alters a cell, the duration depends on the body's ability to regenerate those cells.

Routes of Medication Administration

• Medications must be delivered in the correct amount and location.
• Delivery is determined by the medication's physical/chemical properties, available routes, and how quickly it is needed.
• Bioavailability is the percentage of unchanged medication that reaches systemic circulation.
• Bioavailability is determined by the administration route (except IV route, which has 100% bioavailability) and varies by medication.
• Bioavailability is also relevant for medication sequestered in the GI tract.

Oral, Gastric Tube, and Nasogastric Tube

• Many medications are administered via GI tract routes.
• The patient must be responsive and able to swallow or have a nasogastric or orogastric tube.
• Medication absorption varies after administration.
• Medications may be subject to first-pass metabolism in the liver, which can alter or inactivate the medication before it reaches systemic circulation.
• Metabolism can also occur within the GI tract.
• Patients with liver dysfunction are at higher risk of toxicity when medications are given orally.

Factors Affecting GI Medication Absorption

• GI pH can affect absorption.
• Perfusion of the GI system may be decreased during systemic trauma or shock.

Endotracheal Route

• It is considered an unreliable method of medication administration.
• If used, administer 2 to 2.5 times the IV dose, followed by a 5-10 mL flush of sterile water or normal saline.

Intranasal Route

• Liquid medications are converted into a mist and sprayed into one or both nostrils.
• Absorption is rapid, with bioavailability close to 100% in some studies.
• There is no risk of needle stick injury to the paramedic.

Intravenous (IV) Route

• Often the preferred method in the prehospital setting.
• Involves a small-diameter catheter inserted into a peripheral or external jugular vein.
• Medication is administered directly into systemic circulation, resulting in 100% bioavailability.
• Onset is quicker compared to oral, orogastric, or nasogastric routes.

IV Route Limitations

• Access can be difficult in patients with a history of IV drug abuse, profound shock, or cardiovascular collapse.
• Certain procedures may cause pain or infection and can be time-consuming.
• Sympathomimetics can cause pain and tissue damage.

Intraosseous (IO) Route

• A needle is inserted through the patient's skin and into the bone.
• Vascular uptake from the bone marrow provides a reliable route for medications and IV fluids.
• Any medication that can be given IV can also be given IO.
• Once inserted, it can be left in the hospital for up to 24 hours.
• Contraindicated in fractured bones and discouraged in patients with bone disease or skin infection at the insertion site.

Veins Used for IO Infusion

• The proximal humerus utilizes the axillary vein.
• The proximal tibia utilizes the popliteal vein.

Intramuscular (IM) Route

• Medication is injected into one of the patient's larger muscles.
• Used when IV access cannot be established or when immediate medication administration is required.
• Bioavailability ranges from 75% to 100%.
• There is a risk of contaminated needle stick if the patient moves suddenly.
• Before administering, confirm that the medication is appropriate for IM use.

IM Considerations

• Use the correct muscle for injection.
• Use a specific injection technique.

Subcutaneous (SubQ) Route

• Similar to IM; medication is injected into subcutaneous tissue sites throughout the body.
• Includes the anterior abdomen (just outside the umbilicus) and skin overlying the triceps.
• Some medications are indicated only for subQ use.
• Slower absorption may prevent adverse cardiovascular effects.
• Heparin and insulin are examples of medications administered subQ.

Dermal and Transdermal Route

• Patches commonly contain nicotine, antiemetics, analgesics, or nitroglycerin.
• They may alter a patient's clinical presentation or interfere with other medications.
• Deliver a relatively constant dose of medication over a long period.
• Often contain a large quantity of medication.

Sublingual Route

• Bioavailability is low, requiring larger doses.
• Patients must be conscious and alert.
• A lack of saliva may delay absorption.
• Bioavailability is low.

Inhaled or Nebulized Route

• Inhaled prehospital medications are limited to oxygen and asthma medications.
• Medications have the potential to cause bronchospasms.
• Do not routinely administer calcium lane or other non-traditional medications.

Rectal Route

• Preferred over the oral route if the patient is unresponsive, having seizures, vomiting, or unable to swallow oral medications.
• Medication is usually is not subject to first-pass metabolism.
• Some medications may have greater than 90% bioavailability.
• Administer in the lower rectum rather than the proximal when possible.
• Medications are manufactured in suppository form.
• Absorption can be unpredictable.

Rectal Administration Note

• Use a commercial device, a lubricated feeding tube attached to a syringe, or a lubricated small-diameter syringe.
• Never insert a needle into a patient's rectum.

Ophthalmic Route

• Generally limited to ocular anesthetic agents to facilitate irrigation of eyes following chemical exposure.
• Carries the possibility of systemic toxic effects.

Other Methods of Medication Administration

• Hemodialysis involves pumping blood through a dialysis machine before returning it to the patient; the dialysate solution removes toxins, excess electrolytes, and other chemicals.

Training

• Routes should only be used after proper training has occurred.