Tx of head lice Flashcards
pediculicidal and/or ovicidal action; MOA; ADE; contraindications; Tx for systemic toxicity
Why must pediculicidal agents be administered in 2 or 3 courses of Tx?
life cycle of female louse will alter complete lice eradiations
When should agents that are both pediculicidal and ovicidal be delivered?
1 or 2 courses of Tx one week apart
What is the difference in chemical Tx and physical Tx?
chemical=> paralyze louse; dehydration
physical=> suffocate the louse
What are the most common chemical agents?
malathion; permethrin; lindane; ivermectin
What is causing some chemical agents to not be used?
resistance to permethrin and lindane=> malathion only ovicidal Tx available
How is malathion applied?
topically
How does malathion kill the louse?
metabolized to malaoxon that inhibits acteyl-cholinesterase and causes neuronal hyperstimulation and paralysis
What is the effect of malathion on the human?
rapidly converted to inactive metabolites excreted by kidney
Is there any significant cholinergic activity associated with malathion?
not topically
if ingested oral/pulmonary then increase in GI peristalsis; miosis; deceased ocular accommodation; increased lacrimation; confusion; hypotension; muscular/respiratory paralysis
How should a malathion ingestion be treated?
atropine and pralidoxime
What is the MOA of permethrin?
hyperexcitability and paralysis by binding voltage gated Na channels
What is a rare ADE of permethrin?
asthma exacerbation in patients allergic to ragweed
How do lice gain resistance to permethrin?
knock down resistance mutations of louse Na channels
How does permethrin affect the human?
minimal absorption occurs and if any is then rapidly inactivated by ester hydrolysis
What is Lindane disfavored as Tx for head lice?
neurotoxicity and environmental persistence
When and how is Lindane administered?
shampoo/lotion for patients that cannot tolerate or failed first line Tx w/ safer Rx
What is a significant ADE associated with prolonged use of Lindane?
seizures and deaths
What happens when Lindane is absorbed systemically?
CNS stimulate promoting seizures => ADEs that block GABA action
Who is at the greatest risk in use of lindane?
elderly, underweight, premature infants
Are any black box warnings associated with lindane Tx?
skin diseases/conditions or neonatal prematurity increase systemic damage
Who is lindane contraindicated for?
uncontrolled seizure disorders
What is significant with Tx for ivermectin?
not an option for younger individuals due to immature BBB; viable for adults though
What is the MOA of ivermectin?
hyperexcitability and paralysis by binding selectively and w/ high affinity to glutamate gated Cl ion channels in invertebrate nerve and muscle cells
Is there resistance to ivermectin?
none reported
What is one ADE associated with ivermectin?
worsening bronchial asthma
Why should ivermectin be given in 3 doses at 1 wk intervals?
it is pediculicidal
What are some physical methods for controlling head lice?
benzyl alochol; cetaphil cleanser; dimethicone; shaving head
