DRUG INTERACTIONS

DRUG INTERACTIONS

– Adverse drug effects

– Hypersensitivity

– Anaphylactic reactions

Adverse drug effects

• An unwanted or harmful reaction experienced following the administration of a drug or combination of drugs under normal conditions of use and suspected to be related to the drug

Onset Severity Type

Classification

Onset of event:• Acute

• within 60 minutes• Sub-acute

• 1 to 24 hours• Latent

• > 2 days

Classification

Severity of reaction:•Mild

• bothersome but requires no change in therapy

•Moderate• requires change in therapy, additional

treatment, hospitalization

• Severe• disabling or life-threatening

Classification - Severity

– Result in death

– Life-threatening

– Require hospitalization

– Prolong hospitalization

– Cause disability

– Cause congenital anomalies

– Require intervention to prevent permanent injury

Classification - Severity

•Type A• extension of pharmacologic effect• often predictable and dose dependent• responsible for at least two-thirds of

ADRs• propranolol is given for tachycardia to

reduce heart rate.It can cause heart block due to excessively slowing the heart

Classification

•Type B

• idiosyncratic or immunologic reactions

• rare and unpredictable

• e.g., chloramphenicol and aplastic anemia

Classification

•Type C

• associated with long-term use

• involves dose accumulation

• e.g., antimalarials and ocular toxicity

Classification

•Type D

• delayed effects (dose independent)

• Carcinogenicity (e.g., immunosuppressants)

• Teratogenicity (e.g., fetal hydantoin syndrome)

Classification

Types of allergic reactions• Type I • Type II• Type III• Type IV

Classification- Drug Hypersensitivity

Understanding hypersensitivity

• Our immune system mediates this

• Immune system has lots of cells

• Mast cells are responsible of type 1

• Antibodies cause type 11 and 111

• T cells cause type 1V

Examples

• Type 1-anaphylaxis to drugs

• Type 11-drug induced hemolysis

• Type 111-serum sickness syndrome

Drug-Induced Hemolytic Anemia

• This is where certain antibiotics can absorb to the proteins on RBC membranes

• Examples: penicillin, streptomycin

• Sometimes antibodies cause lysis and thus progressive anemia

• When drug is withdrawn the hemolytic anemia disappears

Serum sickness syndrome

• reaction that develops when antigen is intravenously administered resulting in formation of large amounts antigen-antibody complexes and the deposition in tissue

Risk factors for Drug Allergy

• Frequent exposure to the drug

• Large doses of the drug

• Drug given by injection rather than pill

• Family tendency to develop allergies and asthma.

Anaphylactic Reaction

• Life threatening

• Almost all anaphylactic reactions occur within 4 hours of the first dose of the drug. Most occur within 1 hour of taking the drug, and many occur within minutes or even seconds.

Symptoms of anaphylactic shock

• Skin reaction - Hives, redness/flushing, sense of warmth, itching

• Difficulty breathing - Chest tightness, wheezing, throat tightness

• Fainting - Light-headness or loss of consciousness due to drastic decrease in blood pressure ("shock")

• Rapid or irregular heart beat• Swelling of face, tongue, lips, throat, joints, hands,

or feet

The causative antigens causing anaphylaxis

• Blood products

• ß-lactam antibiotics• X-ray contrast agent• Other drugs

Prophylaxis of anaphylaxis

• Routine skin testing before giving drugs • If X ray contrast is to be used in a patient, the

patient should be pretreated with a steroid if there is a history of allergies

Thank you…