Pharmacokinetics and Routes of Administration

The term “pharmacokinetics” describes how drugs move through the body. Absorption, distribution, metabolism, and excretion are the results of a variety of biochemical processes that they go through.

PHASES OF PHARMACOKINETICS.

ABSORPTION

Absorption is the process by which drugs are transported into the bloodstream from the site of administration (gastrointestinal (GI) tract, muscle, skin, mucous membranes, or subcutaneous tissue). The enteral (via the GI tract) and parenteral (by injection) modes of administration are the most popular. These pathways each have an own pattern of absorption.

Oral

BARRIERS TO ABSORPTION: The layer of epithelial cells that lines the GI system must allow medications to get through.

ABSORPTION PATTERN: Varies greatly due to:

Sublingual, buccal

BARRIERS TO ABSORPTION: Gastric pH can render a drug inactive when it is swallowed prior to breakdown.

ABSORPTION PATTERN: Mucous membranes with high blood flow allow for rapid systemic absorption.

Other mucous membranes (rectal, vaginal)

BARRIERS TO ABSORPTION: The ability to reach the tissues is limited by the presence of stool in the rectum or infectious material in the vagina.

ABSORPTION PATTERN: Simple absorption with both local and systemic effects.

Inhalation via mouth, nose

BARRIERS TO ABSORPTION: Inspiring effort.

ABSORPTION PATTERN: Rapid absorption through networks of alveolar capillaries.

Intradermal, topical

BARRIERS TO ABSORPTION: epidermis cells are located closely together.

ABSORPTION PATTERN

Subcutaneous, intramuscular

BARRIERS TO ABSORPTION: Large gaps exist between cells in capillary walls. Therefore, there isn’t a big barrier.

ABSORPTION PATTERN

Intravenous

BARRIERS TO ABSORPTION: No barriers

ABSORPTION PATTERN

• Immediate: instantly enters the blood

• Complete: touches every part of the blood

DISTRIBUTION

Distribution is the movement of drugs through physiological fluids to their locations of action. Included in the factors affecting distribution are the following.

Circulation: The distribution of medications can be delayed by illnesses that reduce blood flow or perfusion, such as peripheral vascular disease or cardiac disease.

Permeability of the cell membrane: To reach its intended location, the drug must be able to penetrate tissues and membranes. The blood-brain barrier and the placenta can be crossed by drugs that are lipid-soluble or have a transport system.

Plasma protein binding: Drugs compete with one another for the bloodstream’s protein-binding sites, primarily albumin. How well a drug binds to a protein can influence how much of the drug leaves the body and reaches the target tissues. Toxic effects might occur when two drugs fight for the same binding sites.

• Age: The ability of infants to metabolize medications is limited. The metabolism of medications can also be affected by age, however this varies from person to person. Age-related declines in hepatic drug metabolism are generally observed. Because pharmaceutical buildup in the body is a possibility, older persons need reduced doses of their prescriptions.
• Increase in some medication metabolizing enzymes: This may cause a particular medicine to metabolize more quickly, necessitating an increase in dosage to maintain a therapeutic level. It may also speed up the metabolism of drugs being used concurrently.
• First-pass effect: Some drugs require a nonenteral route (sublingual, IV) due to their strong first-pass effect, which causes the liver to inactivate them on their first transit through the liver.
• Similar metabolic pathways: Two drugs being metabolized by the same pathway can cause changes to either one or both of their metabolisms. As a result, one or both of the medications’ rates of metabolism may slow down, which could result in drug accumulation.
• Nutritional status: Malnourished patients may lack certain nutrients necessary for the production of particular enzymes involved in the metabolism of a given medicine, which would interfere with the metabolism of that medication.

• increased drug excretion by the kidneys
• medication inactivation
• Enhanced therapeutic impact
• Activation of pro-drugs into active versions, also known as pro-medications
• Reduced toxicity when drugs’ active versions transform into their inactive counterparts
• Increased toxicity when medication’s inactive forms transform into active forms

• Medications leave the body within 4 to 8 hours.
• MEC drops or a brief pause between dosages.

• More than 24 hours pass before medications exit the body, increasing the risk of drug buildup and toxicity.
• Longer intervals between doses of medication are possible without losing their therapeutic effects.
• The stable state of medications takes more time to develop.

• Vomiting, decreased GI motility, lack of a gag reflex, trouble swallowing, and a decreased level of consciousness are all indicators against using oral medications.
• To make swallowing easier, have customers sit up straight at a 90-degree angle.
• Give irritating medicines, like analgesics, in tiny doses when eating.
• Avoid mixing with huge quantities of food or drink in case customers don’t drink all of it.
• Avoid administering medication with meals or drinks that interact, such as grapefruit juice.
• Follow the advice on whether to take oral drugs with food or on an empty stomach (30 minutes to one hour before meals, two hours after meals). Administer oral medications as directed.
• For crushing, chopping, and dilution of drugs, according to the manufacturer’s instructions. Only break or cut tablets with scoring. (See the webpage of the Institute for Safe Medication Practices.)
• Make sure patients completely ingest time-release or enteric-coated drugs.
• When feasible, take the medication in a liquid form to make swallowing easier.
• Follow the dilution and shaking instructions for liquids, such as suspensions and elixirs. To prepare the medication, set a medicine cup on a flat surface before pouring, and make sure the dose is level with the base of the meniscus (lowest fluid line).

• Safe
• Inexpensive
• Easy and convenient

• Absorption of drugs taken orally varies significantly.
• First-pass effect or the GI tract can also result in inactivation.
• Clients must cooperate and be aware.

• As long as the medication is not completely absorbed, keep it in place.
• Until the tablet has completely dissolved, avoid eating or drinking while it is still in your mouth.

• Use liquid medication forms; if none are available, you might think about crushing pills if the rules allow it.
• Sublingual drugs can be given beneath the tongue; do not provide sublingual meds through the NG tube.
• Avoid crushing oral drugs that have been specifically prepared (extended/time-release, fluid-filled, enteric-coated).
• Separately administer each drug.
• Enteral feedings and medication should not be combined.
• Before administering, thoroughly dissolve the contents of the capsule and any crushed tablets in 15 to 30 mL of sterile water.

• Check the positioning of the tube.
• Use a syringe and either let the medicine fall in naturally or inject it by pushing the plunger.
• Flush the tubing both before and after each dose of medication with 15 to 30 mL of sterile water to prevent blockage.
• Once all the drugs have been infused, flush with an additional 15 to 30 mL of warm, sterile water.

• Painless
• Limited adverse effects

• Apply with a cotton-tipped applicator, glove, or tongue blade.
• Don’t use your bare hands to apply.
• Wash the skin with soap and water before applying anything to it. Before applying, dry off.
• Apply topical treatments to open wounds using surgical asepsis.

• To ensure adequate dose, use patches.
• Before applying a fresh patch, wash the skin with soap and water and thoroughly dry it.
• Apply the patch to a skin-free area, and switch locations every day to prevent skin irritation.

• Ask client to stare up at the ceiling while they are sitting or lying supine.
• Your client should close their eyes softly while you place your dominant hand on their forehead, hold the dropper 1 to 2 cm above the conjunctival sac, drip the drug into the sac, and avoid getting any on the cornea. Repeat the technique if they blink while receiving the medication.
• To stop the drug from being absorbed into the system, gently squeeze the nasolacrimal duct for 30 to 60 seconds using your finger and a clean facial tissue.
• When administering multiple medications to the same eye, allow at least five minutes to pass between each one.
• Apply eye ointment with a thin ribbon from the inner to the outer canthus of the lower eyelid.

  Ear

  • Clients should either lie on their side or sit up straight. Pull the auricle either upward and outward for adults or downward and backward for kids under the age of three to straighten the ear canal. Holding the dropper 1 cm above the ear canal, inject the drug, and then gently press with your finger on the tragus of the ear, unless it is too painful.
  • Do not insert a cotton ball all the way into the ear canal. If required, carefully insert it into the ear canal’s outermost region.
  • After administering ear drops, if at all feasible ask patients to stay in the side-lying position for two to three minutes.

  Nose

  • Using an aseptic procedure while giving medication through the nose.
  • Allowing the drug to enter the proper nasal channel requires that patients lie supine with their heads in the suitable positions.
  • Nasal drops should be administered using your dominant hand while holding the head steady with your non-dominant hand.
  • Give clients instructions to use their mouths to breathe, remain supine, and refrain from blowing their nose for five minutes following the administration of drops. When using a nasal spray, prime it if necessary, nudge the nozzle away from the bridge of the nose, and insert the tip into the nare. As the client inhales, spray into the nose. Tell the client to wait a while before blowing their nose.

  Rectal suppositories

  • Clients should be positioned in Sims’ or the left lateral position.
  • Just past the internal sphincter, insert the suppository.
  • Instruct patients to hold the suppository in place for at least five minutes after insertion by keeping them flat or in the left lateral position. The drug has different times for absorption.

  Vaginal

  • Clients should be positioned in a modified lithotomy or dorsal recumbent position, with their feet level on the bed and close to their hips.
  • If necessary, give peritoneal care.
  • According to the formulation, labricate the suppository or fill the applicator.
  • Insert the drug along the posterior wall of the vagina (75 to 10 cm [3 to 4 in] for suppositories; 5 to 7.6 cm (2 to 3 in) for creams, jellies, or foams) or administer irrigation as directed.
  • Instruct patients to stay supine for at least 5 minutes after insertion in order to retain the suppository. If using a reusable applicator, wash it with soap and water. If it is disposable, discard it.

  INHALATION

  Administered using dry-powder inhalers (DPI) or metered dosage inhalers (MDI)

  MDI

  CLIENT EDUCATION

  • Remove the mouthpiece cap from the inhaler.
  • Five or six vigorous shakes of the inhaler are required.
  • With the mouthpiece at the bottom, hold the inhaler.
  • Your index and middle fingers should be at the top of the inhaler while your thumb should be close to the mouthpiece.
  • You can either close your mouth around the inhaler’s mouthpiece with the opening facing toward the back of your throat or hold the inhaler 2 to 4 cm (1 to 2 in) away from the front of your mouth.
  • Inhale deeply, then let it out.Press the inhaler while tilting your head back slightly, then start taking calm, deep breaths. For 3 to 5 seconds, keep inhaling slowly and deeply to help the medication reach the airways.
  • Take a 10-second breath hold to give the medicine a chance to settle in your airways.
  • Exhale carefully through pursed lips after removing the inhaler from your mouth.
  • breathe normally once more.
  • A spacer prolongs the time that the drug is in the device, increasing the quantity of medication that is delivered to the lungs and reducing the amount that is sent to the oropharynx.
  • Remove the covers from the mouthpieces of the spacer and the inhaler if you are using a spacer.
    • Place the MDI into the spacer’s tip.
    • Five to six shakes of the inhaler.
    • Completely exhale, then seal your mouth around the mouthpiece of the spacer. proceed as though using an MDI.

  DPI

  CLIENT EDUCATION

  • Keep the device from shaking.
  • Take the mouthpiece’s cover off.
  • When placing a drug pellet into an inhaler or rotating the inhaler’s wheel, make sure to follow the manufacturer’s instructions.
  • Completely exhale.
  • Put the mouthpiece between your lips and breathe deeply through your mouth.
  • Take a five to ten second breath hold.
  • With your lips pursed, carefully exhale after removing the inhaler from your mouth.
  • Resume breathing normally.
  • Wait the amount of time recommended by the provider before administering a second puff if more than one is required.
  • If using a corticosteroid inhaler, rinse your mouth thoroughly with water or brush your teeth to lessen the chance of developing a fungal infection in your mouth.
  • Once every day, take out the canister and thoroughly dry the inhaler, cap, and spacer before rinsing them under warm running water.

  PARENTERAL

  NURSING ACTIONS

  • For newborns under one year olds, the vastus lateralis works well.
  • For intramuscular injections (IM) and for injecting volumes more than 2 mL, the ventrogluteal site is preferred.
  • Due to its reduced muscle mass, the deltoid site can only hold 1 mL of liquids.
  • Use a needle that is the right size and length for the injection type and the client’s size. The size of the syringe should roughly match the amount of medicine.
  • When the solution volume is less than 0.5 mL, use a tuberculin syringe.
  • In order to improve drug absorption, rotate injection sites. Record each location.
  • Injection sites with moles, birthmarks, scars, or edema should not be used.
  • Immediately check clients for beneficial and harmful reactions after IV delivery.
  • In leak- and puncture-proof containers, dispose of any sharps, including needles and broken ampule bottles.

  INTRADERMAL

  NURSING ACTIONS

  • Use to test for tuberculin or to check for medication or allergy sensitivity.
  • Use tiny volumes of solution (0.01 to 0.1 mL) in a tuberculin syringe with a fine-gauge needle (- to%-inch, 25- to 27-gauge) at an angle of 10° to 15° in locations with thin skin and light pigmentation, such as the inner surface of the mid-forearm or the scapular region of the back.
  • Bevel up as you insert the needle. There should be a little bleb.
  • Don’t rub the injection site afterward.

  SUBCUTANEOUS AND INTRAMUSCULAR

  NURSING ACTIONS

  Subcutaneous

  • Use for little doses of water-soluble, non-irritating drugs like heparin and insulin.
  • Use a 3/8 to 5/8-inch, 25 to 31-gauge needle. When delivering insulin, use an insulin syringe. No more than 1.5 mL of solution should be injected.
  • Choose areas with suitable fat pad size, such as the thighs, upper hips, and sides of the arms.
  • Pinch up the skin and inject at an angle of 45° to 90° for clients of average size. Use a 90° angle for individuals who are obese.
  • Intramuscular
  • Use for aqueous suspensions, irritant medications, and oil-based solutions.
  • The ventrogluteal, deltoid, and (pediatric) vastus lateralis are the most frequent locations. Due to its closeness to the sciatic nerve, the dorsogluteal is no longer advised as a typical injection site.
  • Use a needle with a gauge of 18 to 25 that is up to 1.5 inches long and inject at a 90-degree angle. Normal solution volumes range from 1 to 3 mL. Use two syringes for bigger quantities, and administer at two distinct sites.

  ADVANTAGES

  • Use for medications that aren’t easily soluble.
  • Use for prolonged administration of medicines with delayed absorption (depot formulations).

  DISADVANTAGES

  • Costs for injections are expensive.
  • Injections are difficult to administer.
  • In addition to the possibility of nerve and local tissue injury, there may be pain.
  • The injection location is susceptible to infection.

  INTRAVENOUS

  NURSING ACTIONS

  • Use to deliver fluids, blood products, and medications.
  • Both long-term (infusion ports) and short-term (catheters) use of vascular access devices are possible. Use 16-gauge equipment for clients who have been injured, 18-gauge equipment for surgeries and blood transfusions, 22- to 24-gauge equipment for kids, seniors, and clients who have medical conditions or are recovering well after surgery.
  • It is best to use peripheral veins in the arm or hand. Ask customers which website they like best. Use the head, feet, and lower legs for babies. Following administration, keep a close eye out for both beneficial and harmful consequences.
  • For IM injections of irritants or fluids that can stain the skin (iron preparations), use the Z-track approach. By using this technique, medication leakage into subcutaneous tissue is avoided.

  ADVANTAGES

  • Rapid onset and fast absorption into the bloodstream result in an immediate reaction.
  • This method gives the ability to precisely manage the dosage of the drug.
  • It makes it possible to provide enormous amounts of fluid.
  • It dilutes irritating drugs in an IV solution that is free to circulate.

  DISADVANTAGES

  • Even more expensive are IV injections.
  • IV treatments are uncomfortable.
  • The medicine immediately enters the bloodstream after administration. Giving the improper dosage or the incorrect drug could be harmful.
  • IV injections carry a higher risk of infection or embolism.
  • The distribution of the drug may be hampered by poor circulation.

  EPIDURAL

  NURSING ACTIONS

  • Use for morphine or fentanyl IV opioid analgesia.
  • At the level of the fourth or fifth vertebra, the doctor inserts the catheter through the needle into the epidural space.
  • To deliver medication, using an infusion pump.