How does pregnancy affect the pharmacokinetics of drug therapy?
Accelerated excretion so dosages must be increased, hepatic metabolism increases for some anti-seizure drugs (phenytoin, carbamazeipine, valproic acid), more time for drugs to be absorbed because tone & motility of the bowel decrease causing intestinal transit time to increase so dosage may need to be reduced
What do you need to know about the impact of drug adverse effects during pregnancy?
Clinician should assume that any drug taken during pregnancy will reach the fetus, the effect of greatest concern is teratogenesis
What are drugs to be concerned about during pregnancy?
Heparin an anticoagulant that can cause osteoporosis and cause compression fractures of the spine, prostaglandins that stimulate uterine contraction and can cause abortion, aspirin that increases risk of serious bleeding, & certain pain relievers during delivery because can depress respirations in neonate
What is the relationship between real stage of development & teratogenesis?
Fetal sensitivity to teratogens changes during development & hence the effect of a teratogen si highly dependent upon when the drug is given
What happens during the preimplantation or presomite period in regards to teratogenesis?
Conception or week 2, if the dose is sufficiency high the result is death of the infant, if the dose is sublethal the infant is likely to recover fully
What happens during the embryonic period in regards to teratogenesis?
Week 3 to week 8, gross malformations are produced by exposure to teratogens, must take special care to avoid during this time
What happens during the fetal period in regards to teratogenesis?
Week 9 to term (2nd or 3rd trimesters), usually disrupts function rather than gross anatomy, growth & development of the brain are important in this stage, results in learning deficits & behavioral abnormalities
What are drugs that should be avoided during pregnancy?
Anticancer/immunosuppressant drugs (cyclophosphamide, methotrexate), anti seizure drugs (carbamazeprine, valproic acid, phenytoin), sex hormones (androgens/danazol, diethylstilbestrol), antimicrobials (nitrofurantion, sulfonamides, tetracycline), & alcohol, angiotensin-converting enzyme inhibitors, antithyroid drugs, non steroidal anti-inflammatory drugs, lithium, oral hypoglycemic drugs, isotretinoin & other vitamin A derivatives, thalidomide, warfarin
What are category A FDA pregnancy risks?
Remote risk for fetal harm, controlled studies in women have been done & have failed to demonstrate a risk for fetal harm during the first trimester and there is no evidence of risk in later trimesters
What are category B FDA pregnancy risks?
Slightly more risk than A
What are category C FDA pregnancy risks?
Slightly more risk than B
What are category D FDA pregnancy risks?
Proven risk of fetal harm, studies in women have shown proof of fetal damage but the potential benefits may be acceptable despite the risks, statement on risk will appear in the warnings section of drug label
What are category X FDA pregnancy risks?
Proven risk of fetal harm, studies in women & animals show definite risk of fetal abnormalities or adverse reaction reports indicated evidence of fetal risk, risks clear outweigh any possible benefit, state will appear on contraindications section of label
Can known teratogenic drugs ever be used in pregnancy?
Some disease states such as epilepsy, asthma, & diabetes prose a greater risk of fetal health than do drugs for that treatment, must take steps to minimize harm, drugs that pose high risk will be discontinued & safer alternatives substituted
What are drugs that are contraindicated during breast feeding?
Controlled substances like amphetamine, cocaine, heroin, marijuana, phencyclidine; anticancer agents/immunosuppressants like cyclophosphamide, cyclosporine, doxorubicin, & methotrexate; others like bromocriptine, ergotamine, lithium, & nicotine
Infants are at risk for drug toxicity due to what?
Decreased liver enzymes, reduced kidney perfusion, reduced liver perfusion
How are pharmacokinetics different for a geriatric client?
Gastric acidity is reduced so drugs that require high acidity to dissolve will have reduced absorption, increased percent of body fat causes reduction of responses, decreased percent lean body mass & decreased total body water cause drug effects to be more intense, reduced concentration of serum albumin cause drug effects to be more intense, rate of hepatic drug metabolism decreases, prolonged response due to decreased liver function, renal function declines
What is the most important cause of adverse drug reactions in the elderly?
Drug accumulation due to reduced renal excretion
What factors affect development of adverse drug reactions in geriatric clients?
Drug accumulation due to reduced renal function, polypharmacy, greater severity of illness, presence of multiple pathologies, greater use of drugs with low therapeutic index, increased individual variation due to altered pharmacokinetics, inadequate supervision of long term therapy, poor patient adherence
What measures can help geriatric patients stay compliant with drug therapy?
Simplify the regimen so that the number of drugs & doses per day is as small as possible, explain the treatment plan using clear, concise verbal & written instruction, choose an appropriate dosage form (liquid best if pt. has trouble swallowing), label drug containers clearly & avoid containers that are difficult to open, ask patient if they have access to pharmacy & can afford their meds, enlist the aid of others, monitor for therapeutic response, adverse effect, & plasma drug levels