Tx of head lice

Question 1

Why must pediculicidal agents be administered in 2 or 3 courses of Tx?

Answer 1

life cycle of female louse will alter complete lice eradiations

Question 2

When should agents that are both pediculicidal and ovicidal be delivered?

Answer 2

1 or 2 courses of Tx one week apart

Question 3

What is the difference in chemical Tx and physical Tx?

Answer 3

chemical=> paralyze louse; dehydration

physical=> suffocate the louse

Question 4

What are the most common chemical agents?

Answer 4

malathion; permethrin; lindane; ivermectin

Question 5

What is causing some chemical agents to not be used?

Answer 5

resistance to permethrin and lindane=> malathion only ovicidal Tx available

Question 6

How is malathion applied?

Answer 6

topically

Question 7

How does malathion kill the louse?

Answer 7

metabolized to malaoxon that inhibits acteyl-cholinesterase and causes neuronal hyperstimulation and paralysis

Question 8

What is the effect of malathion on the human?

Answer 8

rapidly converted to inactive metabolites excreted by kidney

Question 9

Is there any significant cholinergic activity associated with malathion?

Answer 9

not topically
if ingested oral/pulmonary then increase in GI peristalsis; miosis; deceased ocular accommodation; increased lacrimation; confusion; hypotension; muscular/respiratory paralysis

Question 10

How should a malathion ingestion be treated?

Answer 10

atropine and pralidoxime

Question 11

What is the MOA of permethrin?

Answer 11

hyperexcitability and paralysis by binding voltage gated Na channels

Question 12

What is a rare ADE of permethrin?

Answer 12

asthma exacerbation in patients allergic to ragweed

Question 13

How do lice gain resistance to permethrin?

Answer 13

knock down resistance mutations of louse Na channels

Question 14

How does permethrin affect the human?

Answer 14

minimal absorption occurs and if any is then rapidly inactivated by ester hydrolysis

Question 15

What is Lindane disfavored as Tx for head lice?

Answer 15

neurotoxicity and environmental persistence

Question 16

When and how is Lindane administered?

Answer 16

shampoo/lotion for patients that cannot tolerate or failed first line Tx w/ safer Rx

Question 17

What is a significant ADE associated with prolonged use of Lindane?

Answer 17

seizures and deaths

Question 18

What happens when Lindane is absorbed systemically?

Answer 18

CNS stimulate promoting seizures => ADEs that block GABA action

Question 19

Who is at the greatest risk in use of lindane?

Answer 19

elderly, underweight, premature infants

Question 20

Are any black box warnings associated with lindane Tx?

Answer 20

skin diseases/conditions or neonatal prematurity increase systemic damage

Question 21

Who is lindane contraindicated for?

Answer 21

uncontrolled seizure disorders

Question 22

What is significant with Tx for ivermectin?

Answer 22

not an option for younger individuals due to immature BBB; viable for adults though

Question 23

What is the MOA of ivermectin?

Answer 23

hyperexcitability and paralysis by binding selectively and w/ high affinity to glutamate gated Cl ion channels in invertebrate nerve and muscle cells

Question 24

Is there resistance to ivermectin?

Answer 24

none reported

Question 25

What is one ADE associated with ivermectin?

Answer 25

worsening bronchial asthma

Question 26

Why should ivermectin be given in 3 doses at 1 wk intervals?

Answer 26

it is pediculicidal

Question 27

What are some physical methods for controlling head lice?

Answer 27

benzyl alochol; cetaphil cleanser; dimethicone; shaving head