Chapter : Sources and Bodily Effect of Drugs

Transcription

1 Systemic Effect- drug acts in a widespread area away from the administration site Ex: Tylenol rectal suppository- given rectally but is absorbed and distributed thru the body to cause a reduction in fever and pain Chapter : Sources and Bodily Effect of Drugs Local effect- limited to the area of the body where it is administered Ex: Nupercainal (dibucaine) applied rectally affecting only the rectal mucosa to reduce hemorrhoidal pain Drug: Any chemical substance taken into the body for the purpose of affecting body function Drugs are used in medicine to prevent, diagnose, or treat a disease or abnormal condition Source of drugs: Plants Minerals Animals Synthetics (see chart on pg 27 for examples) Absorption- drug gets into the bloodstream Distribution- from the bloodstream into the tissues and fluids of the body Metabolism- physical and chemical changes that a drug undergoes in the body (most often by liver) Excretion- eliminating waste products of drug metabolism from the body (primarily happens in kidney) 1

2 Absorption - food may affect drug absorption Ex: tetracycline should be given on an empty stomach. If given with dairy or antacids it will alter the ph of the stomach and interfere with absorption Ex: Biaxin XL should be taken with food (may not work as well on empty stomach) ******Do not crush or chew extended or controlled release medications. This will cause the medication to be released all at once and could lead to an overdose Drug Metabolism Liver damage (hepatitis, cirrhosis) may prevent drug breakdown and cause build up of unmetabolized drug Drug metabolism Distribution Poor circulation (impaired blood flow) may prevent a drug from reaching the tissues Some drugs have selective distribution- affinity of a drug to a specific organ or cells Ex: amphetamines to the CSF HCG to the ovaries Elimination Most drugs are eliminated by the kidneys. Renal damage or kidney failure may prevent the elimination of drug waste products causing accumulation of drug in the body and increased effect (cumulative effect). This can lead to a toxic drug level. 2

3 Toxicity- condition of exposure to poison or dangerous amount of drug that is normally safe in small amounts. This is of particular concern with drugs of a narrow therapeutic index -pharmaceuticals having a narrowly defined range between risk and benefit. Table ENwarn.pdf These are some of the medications that have a narrow therapeutic index and have to be monitored closely Lanoxin (digoxin)- for atrial fibrillation & heart failure Coumadin (warfarin)- anticoagulant Dilantin (phenytoin)- treats seizures Eskalith, Lithobid (lithium)- treats mood disorders like bipolar disorder Theo-Dur, Theo-24, Uniphyl (theophylline)- treatment of various lung diseases like asthma, emphysema and chronic bronchitis. Tegretol (carbamazepine)- treats seizures Age- different considerations for elderly and children Weight- some medications are dosed by weight Gender- body mass different from female to male. Also must take into account if women are pregnant or nursing Psychological state- placebo effect-patient has a more positive response to medication if they feel good about the medication 3

4 Synergism-two drugs working together for an effect that neither could produce alone. This may be intentional from the prescriber (desirable synergism) or in the case of the prescriber not being aware of all the medications it could be an undesirable synergism and a change would need to be made in therapy. Potentiation- the action of two drugs in which one prolongs or multiplies the effect of the other.(desirable vs. undesirable) Antagonism- the opposing action of two drugs in which one decreases or cancels out the effect of the other(desirable- narcotic antagonist naloxone cancels out effect of narcotics vs. undesirableantacids taken with tetracycline) Routes of Administration: Different ways drugs can enter the body Enteral-Drug administration involving any part of the gastrointestinal (GI) tract Examples: Oral (p.o.): tablets, capsules, liquids- easiest but the effects are slower because of dissolution time of drug in the alimentary canal before absorption Rectal suppositories Nasogastric tube (NG) Minimum dose- smallest amt of a drug that will produce a therapeutic effect Maximum dose- Largest amt of a drug producing a desired effect without symptoms of toxicity Loading dose- Initial high dose (often max dose) used to quickly elevate the level of drug in the blood (often followed by lower maintenance doses) Maintenance dose- dose that keeps drug blood level at a steady state in order to maintain effect Toxic dose- amt of drug producing harmful side effects or symptoms of poisoning Lethal dose- dose that causes death Therapeutic dose- dose that is usually given based on average adult body weight of 150 lbs. Parenteral any route of administration outside the GI tract. Route of choice when patient is NPO or when drug is not suitable for GI absorption Subcutaneous (SC) Intramuscular (IM)- fairly rapid absorption because muscles are highly vascular Intradermal (ID) Intravenous (IV)- administered by Dr., RN or paramedic Best for emergencies because of its fast action Given as IV push or bolus(concentrated drug solution) Or can be diluted and infused more slowly by drip Intracardia, Intraspinal, Intracapsular Sublingual (SL) under the tongue***** Buccal (cheek)***** ****some consider SL and Buccal as oral routes 4

5 Topical Dermal Transdermal- slower consistent drug absorption over time allowing the patient to usually place one patch on in the morning for entire day mucosal Inhalation Fast acting due to large surface area of the lung and rich blood supply which allow the drug to enter the blood stream quickly. But requires patient cooperation and education to be effective. Hypersensitivity- immune response (allergy) to a drug may be of varying degrees. May be mild with no immediate effects, rash may appear after 3 to 4 days of drug therapy May develop after uneventful previous uses of a drug More likely to exist in patients with other known allergies Anaphylactic reaction- severe, possibly fatal allergic rxn. Anaphylaxis happens quickly after the exposure,within seconds or minutes, and often involves the whole body. Signs include: itching, hives, hyperemia, vascular collapse, shock, cyanosis, laryngeal edema and dyspnea Treatments: Benadryl to suppress histamine, epinephrine to raise BP, a corticosteroid to reduce inflammation and the body s immunological response and CPR if needed ********always be aware if a patient has any known allergies Teratogenic effect- can cause developmental defects in a fetus of a pregnant woman Idiosyncrasy- unique, unusual response to a drug. Paradoxycal effect- Opposite effect from the expected (a tranquilizer causing agitation and excitement rather than tranquility) Tolerance- decreased response to a drug that develops after repeated doses are given. To achieve desired effect the dosage must be increased or the drug changed Dependance- acquired need for a drug that may produce symptoms of withdrawal when drug is discontinued Psychological dependence-only psychological craving, no physical symptoms of withdrawal Physical dependence-cells actually have a need for the drug; symptoms of withdrawal include retching, nausea, pain, tremors, sweating 5