Drug Administration Rights and Methods

Drug Administration Rights

• Concentration of drug in the body that produces the desired effect is important, along with minimal or no signs of toxicity or lack of effect.
• Patient identity must be verified.
• Administering a drug at the correct time maintains desired therapeutic effect and avoids toxicity.
• Verify the correct drug four times: removal from storage, dispensing, when returning to the pharmacy, and before giving to the patient.
• Right drug strength is important.
• Right documentation is crucial, including legal and safety obligations requiring the owner's consent to treatment.
• The correct route and technique, patient weight, and dosage must also be correct.

Methods of Drug Administration

Drug Dosage

• The mass of drug required per unit of body weight (e.g., 2 mg/kg).
• Calculated mass of drug administered at one time (e.g., dose = drug dosage x body weight).

Drug Dose Interval

• The frequency at which a dose is administered (e.g., every 24 hours).

Dose Forms

• Physical form of the drug (e.g. oral, intravenous, etc).

Loading Dose

• An increased initial dose to quickly reach the therapeutic range.

Maintenance Dose

• The dose that keeps the drug within the therapeutic range.
• Total Daily Dose = the mass of drug given over 24 hours.

Therapeutic Index (TI)

• A higher TI indicates a safer drug.
• TI = LD50/ED50
• LD50 = Lethal Dose in 50% of patients
• ED50 = Effective dose in 50% of patients.

High vs Low Margin of Safety

• High margin of safety means the lethal dose is much higher than the effective dose. Drug has a high therapeutic index.
• Low margin of safety means the lethal dose is close to the effective dose. Drug has a low therapeutic index.

Routes of Administration (Parenteral)

• Excludes the small intestine (enteral routes).
• IV Injection: Fastest way to achieve drug effects with immediate response and 100% bioavailability.
• Know the concentration of drug in the blood

Routes of Administration (Local)

• Inhalant: Rapid absorption due to a large surface area, drug turns into a gas, nebulised -- Drug turns into a fine spray/ mist. (lung-> alveoli -> blood capillaries)
• Topical

Other Routes of Administration

• Skin, eyes, ears: Dissolution, penetration, diffusion, localized treatment.
• Oral Administration: Slower onset than parenteral routes, does not need to be sterile. Requires 3 events: Dissolution, Liberation, Passage through GI tract and vasculature.

Pharmacokinetics (PK)

• Absorption: Movement from administration site into the blood (vascular system). Affected by: Patient characteristics and dose form.
• Distribution: Movement to tissues. Affected by Body construction, function, route (eg;Solubility, Ionization, molecule size, pKa of Drug), pH of environment Drug is in, vascular system.
• Metabolism: Chemical alterations, primarily in the liver. Affected by various factors including, liver , kidneys, small intestine, etc.
• Excretion: Elimination from body. Primarily through urine or bile; consideration for milk in lactating animals. Affected by Various pathways (kidney, liver, lungs, saliva, intestine, sweat).

Pharmacodynamics (PD)

• Effect of drug on the body including depression, stimulation, destruction, irritation, and replacement.
• Mechanisms for Drug Movement:
• Passive Diffusion: Movement from high to low concentration; requires no energy.
• Facilitated Diffusion: Requires carrier proteins, no energy.
• Active Transport: Requires energy, moves against the concentration gradient.
• Pinocytosis and Phagocytosis: "Cell drinking" and "cell eating"