Medication Action

MEDICATION ACTION

Medications vary considerably in the way they act and their types of action. It is important for a nurse to understand all the effects of a medication when taken by the client.

1.     Therapeutic effect:

The therapeutic effect is the expected or predictable physiological response a medication causes. Each medication has a described therapeutic effect for which it is prescribed. Also called desired effect. E.g.: Nitro glycerine is used to reduce the cardiac workload and  increases the myocardial blood supply.

·        A single medication may have a many therapeutic effect. E.g.: Aspirin is an analgesic, Antipyretic, Ant inflammatory, and reduces platelet aggregation.

·        It is important for the nurse to know for which therapeutic effect the medication is prescribed.

2.     Side effects:

A side effect is when a medication predictably will cause unintended, secondary effects. Side effects may be harmless or injurious. If the side effects are serious, the prescriber must   discontinue the medication.

3.     Adverse effect:

·        Adverse effects are generally considered as severe response to medication.

·        Unintended, undesirable, unpredictable.

·        When adverse effect responses to medication occurs, the prescribes must discontinue the medication.

·        Adverse effects can result from excessive therapeutic effects (e.g. severe hypotension when an antihypertensive drug is administered).

·        Some adverse effects are minor (e.g. Constipation) and can be treated easily.

·        Others may pose serious health risk for the client (e.g. Respiratory depression).

4.     Toxic effects:

·        Toxic effects may develop after a prolonged intake of a medication or a medication accumulates in the blood because of impaired metabolism or excretion.

·        Excess amount of a medication with in the body may have lethal effects, depending on the medication action.

·        Antidotes are available for specific types of medical toxicity. E.g.: Toxic level of   Morphine may cause severe respiratory distress and death.

·        Some drugs produce toxic effects immediately whereas others take days or weeks.

·        Toxicity tan affect and permanently damage organ function.

·        Common drug toxicities include nephrotoxicity (kidney), neurotoxicity (brain)  Hepatotoxicity (liver) immunotoxicity (immune system) ototoxicity (hearing) and cardiotoxicity (heart)

5.     Idiosyncratic reaction:

Medications may cause unpredictable reactions such as idiosyncratic reactions in   which a client overreacts or under reacts to a medication or has a reaction differ from normal. E.g.:  A child receiving an anti-histamine may become extremely agitated or excited, instead of drowsy.

6.     Allergic reaction:

·        Allergic reactions are another unpredictable response to a medication. A client can react to a medicine as a foreign body, and thus develops allergic reactions.

·        Allergic reactions can either be severe or mild. A severe allergic reaction usually occurs immediately after administering-- the medication, known as anaphylactic reactions.

·        Allergic reactions develop from an immunologic response to a medication to which the client has been sensitized. A foreign substance or antigen has been in to the body, and the body responds by producing antibodies.

·        Mild allergic reactions are manifested by hives (urticaria), Pruritus or rhinitis and can occur within minutes to 2 weeks after medication.

Anaphylactic reactions:

·        This is an immediate reaction marked by a decreased blood pressure, local edema, prickling feeling in the throat, Edema on face, Cyanosis, dyspnoea, and obstructed airway. Unless acted quickly, death may follow with in few minutes. E.g.: Sera and Penicillin should be administered only after a sensitivity test.

·        Severe allergic reactions producing symptoms such as wheezing, Dyspnea, angioedema (edema due to increased capillary permeability) of the tongue and oropharynx hypotension and tachycardia occur immediately after the medication is given.

·        Treatment include discontinuing medication and administering epinephrine. IV fluids, steroids and antihistamines.

·        Avoid future exposure, keep an identification bracelet of allergy.

Mild reactions:

Utricaria: Raised, irregularly shaped skin eruptions, with varying sizes and shapes: have reddened margin and pale centers.

Eczema: Small raised vesicles that are usuaIIy reddened often distributed over body. 

Pruritis: Itching of skin with rashes.

Rhinitis: Inflammation of mucus membranes of lining of nose, causes swelling and clear   watery discharge.

Lacrimal tearing

Shortness of breath      

7.     Medication Interactions:

When one medication modifies the action of another medication, a medication interaction occurs.

·        A medication may potentiate or diminishes the action of other medication and may or may not alter the way in which other medication is absorbed, metabolized or eliminated from the body.

·        When two medication have a synergistic effect, or act synergistically, the effect of two combined medication is greater than the effect when given separately.

·        Often a physician orders combination of medication therapy to create a medication interaction for the client's therapeutic benefit. E.g. Person with moderate hypertension typically receives several medications such as diuretics and vasodilators, that act toget her to control the BP.

·        Interaction also can result in antagonism by which drug effects decrease. Sometimes foods influence a drug e.g. Deactivation of antibiotic tetracycline by diary products.

8.     Drug tolerance:

·        A drug tolerance exist in a person who has usually low physiologic response to a drug and required increase in the dosage to maintain a given therapeutic effect.

·        Some agents that produce tolerance include nicotine, alcohol, opiates and barbiturates.

Cumulative effect: is the increasing response to repeated doses of a drug that occurs when the rate of administration exceeds the rate of metabolism or excretion. As a result, the amount of -the drug builds up in the client's body unless the dosage is adjusted. Toxic symptoms may occur.

Drug Incompatibility:

In some cases a drug will precipitate from solutions or chemically in activate if mixed with  other medications. This is known as drug incompatibility. When giving two medications in a  syringe or when mixing IV medications in tubing, it is important to assess whether the drugs  are compatible and can safely be mixed during administration.