Background

Humans act as hosts to three species of louse; Pediculus capitis (head lice), Pediculus corporis (body lice) and Pediculus pubis (pubic lice). Only head lice are discussed in this section.

Prevalence and epidemiology

Head lice affect all ages, although they are much more prevalent in children aged 4 to 11 years, especially girls. Studies conducted in schools show wide variation of current lice infestation ranging from 4 to 22% of pupils. Head lice can occur at any time and do not show any seasonal variation. Most parents will have experienced a child who has head lice, or received letters from school alerting parents to head lice infestation within the school.

Aetiology

Head lice can only be transmitted by head-to-head contact. Fleeting contact will be insufficient for lice to be transferred between heads. Once transmitted lice begin to reproduce. The adult louse lives for approximately 1 month. Throughout this time the female louse lays several eggs at the base of a hair shaft each night. Eggs hatch after 7 to 10 days, leaving the egg case attached to the hair shaft (known as a ‘nit’). In the course of maturing to adulthood the young louse (the nymph) undergoes three moults. Shortly after maturing, the female louse is sexually mature and able to mate.

Arriving at a differential diagnosis

Most parents will diagnose head lice themselves or be concerned that their child has head lice because of a recent local outbreak at school. Occasionally parents will also want to buy products to prevent their child contracting head lice. It is the role of the pharmacist to confirm a self-diagnosis and stop inappropriate sales of products. It should also be remembered that an itching scalp in children is not always due to head lice and other causes should be eliminated. Asking a number of symptom-specific questions should enable a diagnosis of head lice to be easily made (Table 9.1).

Clinical features of head lice

Unless live lice have been found, most patients will present with scalp itching. Itching is caused due an allergic response of the scalp to the saliva of the lice and can take weeks to develop. However, only a third of patients experience itching. Head lice are most commonly found in the occipital and auricular areas.

Conditions to eliminate

Evidence base for over-the-counter medication

Treatment options include insecticides, wet combing and physical agents. All treatments available in the UK have shown varying degrees of clinical effectiveness. It is however difficult to assess which treatment is most effective as very few comparative trials have been performed, and insecticidal resistance varies from region to region. No treatment is 100% effective and failure has been linked with poor adherence to each treatment regimen. Of the treatment approaches, insecticides have been most studied. These include malathion, permethrin, carbaryl and phenothrin – the latter two are now not commercially available. Cure rates of 70 to 80% are reported with insecticides in recent clinical trials, although resistance to insecticides is now a serious problem and appears to be increasing. Wet combing is an alternative treatment option, however, cure rates are reported to be only 40 to 60% with the low cure rates attributed to poor adherence (Roberts et al 2000; Hill et al 2005).

Dimeticone is a recent introduction to the market, and is thought to work by coating the lice both internally and externally, which leads to disruption in water excretion causing the gut of the lice to rupture from osmotic stress (Burgess 2009). Its inclusion in treatment options seems to stem from 1 robust trial conducted by Burgess et al (2005). Dimeticone was compared against phenothrin with cure rates determined at days 9 and 14. Dimeticone was shown to have comparable cure rates to phenothrin (69% compared to 78%). The study has been criticised for using dry detection methods and using different detection days (days 5 and 12 as recommended by the department of health), however a further trial in 2007 supports the 2005 trial results. In the latter study, 4% dimeticone lotion, applied for 8 hours or overnight was compared to 0.5% malathion liquid applied for 12 hours or overnight. The results found dimeticone was significantly more effective than malathion, with 30/43 (70%) participants cured using dimeticone compared with 10/30 (33%) using malathion.

Isopropyl myristate is a recent introduction to the UK market. Like dimeticone it is pharmacologically inert but works by blocking the tracheal breathing system and coating the surface of lice with a thin film of fluid (Drugs and Therapeutics Bulletin 2009). Evidence of efficacy comes from 2 trials that compared isopropyl myristate against permethrin. Results found isopropyl myristate was significantly more effective than permethrin (82% vs 19%). Although these results seem impressive, the comparator drug was permethrin – a product not recommended due to its poor efficacy.

Other non-insecticidal methods of eradication are also promoted. These include herbal remedies such as tea tree oil or essential oils (e.g. Lyclear SprayAway), coconut oil (Lice Attack, Nitlotion) and electric combs. No credible evidence exists on the effectiveness of these products and should not be recommended until such time that data supports their use.

In summary, treatment used will be driven by individual preference, the patient’s medical history and previous exposure to treatment regimens. Wet combing (available as bug busting kits) is time consuming and requires patient motivation but is helpful in areas of high insecticidal resistance. Insecticides, dimeticone and isopropyl myristate are simpler to use than bug-busting kits and appear to have higher cure rates. Based on current evidence it seems dimeticone is treatment of choice.

Practical prescribing and product selection

Prescribing information relating to medicines for head lice reviewed in the section ‘Evidence base for over-the-counter medication’ is discussed and summarised in Table 9.2; useful tips relating to patients presenting with head lice are given in Hints and Tips Box 9.1. All products have to be used more than once; insecticides have to be repeated 7 days after first application (this is based on expert opinion, as the second application is intended to kill nymphs emerging from eggs that have survived the first application); wet combing every 4 days for at least 2 weeks. Coating agents, dimeticone and isopropyl myristate also have to be repeated after 7 days.

All products, except isopropyl myristate, can be used on children older than 6 months. Dimeticone or wet combing is recommended for pregnant and breastfeeding women. When applying all products, pay particular attention to the areas behind the ears and at the nape of the neck, as these areas are where lice are most often found.

Anon. Update on treatments for headlice. DTB. 2009;47:50–52.

Burgess, IF. The mode of action of dimeticone 4% lotion against head lice, Pediculus capitis. BMC Pharmacol. 2009;9(1):3.

Burgess, IF, Brown, CM, Lee, PN. Treatment of head louse infestation with 4% dimeticone lotion: randomised controlled equivalence trial. Br Med J. 2005;330:1423–1425.

Hill, N, Moor, G, Cameron, MM, et al. Single blind, randomised, comparative study of the Bug Buster kit and over the counter pediculicide treatments against head lice in the United Kingdom. Br Med J. 2005;331:384–387.

Roberts, RJ, Casey, D, Morgan, DA, et al. Comparison of wet combing with malathion for treatment of head lice in the UK: a pragmatic randomised controlled trial. Lancet. 2000;356:540–544.

Anon. Management of headlice in primary care. MeReC Bulletin. 2008;18(4):2–7.

Burgess, IF, Brown, CM, Peock, S, et al. Head lice resistant to pyrethroid insecticides in Britain. Br Med J. 1995;311:752.

Burgess, IF, Lee, PN, Matlock, G. Randomised, controlled, assessor blind trial Comparing 4% dimeticone lotion with 0.5% malathion liquid for head louse infestation. PLoS ONE. 2007;2(11):e1127. doi:10.1371/journal.pone.0001127

Connolly, M. Current recommended treatments for headlice and scabies. The Prescriber. 2011;Jan:26–39.

Dodd, CS. Interventions for treating headlice. Cochrane Database of Systematic Reviews. (Issue 4):2006. (Status withdrawn Issue 2, 2012, pending update)

Community Hygiene Concern. http://www.chc.org/bugbusting/

Pediculosis.com. http://www.pediculosis.com/

Once a week – take a peek. http://www.onceaweektakeapeek.com/.

Background

Worm infections are extremely common both in the developed and developing world. In Western countries the most common worm infection is threadworm (known in some countries as pinworm), which is a condition that causes inconvenience and embarrassment. Social stigma surrounds the diagnosis of threadworm, with many patients believing that infection implies a lack of hygiene. This belief is unfounded as infection occurs in all social strata. The patient might benefit from reassurance from the pharmacist, explaining that the condition is very common and is nothing to be ashamed or embarrassed about.

Prevalence and epidemiology

Threadworm is the most common helminth infection throughout temperate and developed countries. Threadworm prevalence is difficult to establish due to the high number of people who self medicate or are asymptomatic. However, UK prevalence rates have been estimated at 20% in the community, rising to 65% in institutionalised settings. Threadworms are much more common in school or pre-school children than adults, because of their inattention to good personal hygiene.

Aetiology

Eggs are transmitted to the human host primarily by the faecal–oral route (autoinfection) but also by retroinfection and inhalation. Faecal–oral transmission involves eggs lodging under fingernails, which are then ingested by finger sucking after anal contact. Retroinfection occurs when larvae hatch on the anal mucosa and migrate back into the sigmoid colon. Finally, threadworm eggs are highly resistant to environmental factors and can easily be transferred to clothing, bed linen and inanimate objects (e.g. toys) resulting in dust-borne infections. Once eggs are ingested, duodenal fluid breaks them down and releases larvae, which migrate into the small and large intestines. After mating, the female migrates to the anus, usually at night, where eggs are laid on the perianal skin folds, after which the female dies. Once laid, eggs are infective almost immediately. Transmission back into the gut can then take place again via one of three mechanisms outlined above and so the cycle is perpetuated.

Arriving at a differential diagnosis

Threadworm diagnosis should be one of the more simple conditions to diagnose as patients present with very specific symptoms.

Clinical features of threadworm

Night-time perianal itching is the classic presentation (caused from the mucus produced by females when laying eggs). However, patients might experience symptoms ranging from a local ‘tickling’ sensation to acute pain. Any child with night-time perianal itching is almost certain to have threadworm. Itching can lead to sleep disturbances resulting in irritability and tiredness the next day. Diagnosis can be confirmed by observing threadworm on the stool, although they are not always visible.

Complicating factors such as excoriation and secondary bacterial infection of the perianal skin can occur due to persistent scratching. The parent should be asked if the perianal skin is broken or weeping.

Conditions to eliminate

Evidence base for over-the-counter medication

Mebendazole and piperazine are available OTC for the treatment of threadworm. There is a large body of evidence to support the effectiveness of mebendazole in roundworm infections but for other worm infections, including threadworm, cure rates are lower. For threadworm, cure rates between 60 and 82% for single-dose treatment of mebendazole have been reported (Rafi et al 1997; Sorensen et al 1996).

Piperazine appears to have less evidence supporting its effectiveness than mebendazole. One study has compared piperazine against mebendazole and found mebendazole to have a higher cure rate than piperazine; although the number of patients in the trial was low.

The difference in cure rates might be, in part, due to their respective mechanism of action. Mebendazole inhibits the worm’s uptake of glucose, thus killing them, whereas piperazine only paralyses the worm (if paralysis wears off then the worm might be able to migrate back into the colon and thus treatment would fail). To optimise worm clearance from the gut piperazine formulations also contain senna.

Practical prescribing and product selection

Prescribing information relating to medicines for threadworm reviewed in the section ‘Evidence base for over-the-counter medication’ is discussed and summarised in Table 9.3; useful tips relating to patients presenting with threadworm are given in Hints and Tips Box 9.2.

Treatment should ideally be given to all family members and not only the patient with symptoms, as it is likely that other family members will have been infected even though they might not show signs of clinical infection. A repeated dose 14 days later is often recommended to ensure worms maturing from ova at the time of the first dose are also eradicated.

Mebendazole and piperazine should be avoided in pregnancy because foetal malformations have been reported but appear safe in breastfeeding. Pregnant women should be advised to practise hygiene measures for 6 weeks to break the cycle of infestation. If treatment is absolutely essential, piperazine has been used, although this should not be in the first trimester.

Rafi, S, Memon, A, Billo, AG. Efficacy and safety of mebendazole in children with worm infestation. J Pak Med Assoc. 1997;47:140–141.

Sorensen, E, Ismail, M, Amarasinghe, DK, et al. The efficacy of three anthelmintic drugs given in a single dose. Ceylon Med J. 1996;41:42–45.

Albonico, M, Smith, PG, Hall, A, et al. a randomized controlled trial comparing mebendazole and albendazole against Ascaris, Trichuris and hookworm infections. Trans R Soc Trop Med Hyg. 1994;88:585–589.

Anon. Merec Bulletin. Management of threadworms in primary care. 1998;18:11–13.

Zaman, V. Other gut nematodes. In: Weatherall DJ, Ledingham JGG, Warrell DA, eds. Oxford textbook of medicine. Oxford: Oxford University Press, 1987.

Background

There is no universally agreed definition of colic. A widely used definition of colic is that proposed by Wessel et al (1954) and has come to be known as the ‘rule of threes’. Wessel proposed that an infant could be considered to have colic if it cries for more than 3 hours a day for more than 3 days a week for more than 3 weeks. However, the definition by Wessel is arbitrary and few parents are willing to wait 3 weeks to see if the infant meets the criteria for colic. As a result the third criterion is usually dropped in the clinical setting. In addition, some authors have defined crying for as little as 90 minutes per day as excessive. Regardless of which definition is used, persistent crying is a cause of stress and anxiety to parents.

Prevalence and epidemiology

Due to no universally accepted definition of colic its prevalence is difficult to determine, and estimates vary widely from 3 to 40% dependent on which definition is used. Studies reporting lower figures strictly applied Wessel’s criteria, whilst higher figures used wider definitions. It is likely that prevalence falls between the two extremes and affects 10 to 20% of infants.

Colic starts in the first few weeks of life and usually resolves by the age of 3 to 5 months.

Aetiology

The cause of colic is poorly understood but seems to be multifactorial. It has been linked to a disorder of the GI tract, where spasmodic contraction of smooth muscle causes pain and discomfort, which might be caused by allergy to cow’s milk or lactose intolerance. It has also been suggested that it might stem from emotional, behavioural and social problems that include underdeveloped parenting skills, inadequate social network, postpartum depression, and parental anxiety and stress.

Arriving at a differential diagnosis

It can be difficult to determine if the baby has colic or is just excessively crying, as the diagnosis of the condition is dependent on qualitative descriptions. However, the term colic is often wrongly applied to any infant who cries more than usual. Asking a number of symptom specific questions should enable a diagnosis of colic to be made (Table 9.4).

Clinical features of colic

Excessive crying and inconsolable crying are obvious clinical features. Pain may be mild, merely causing the child to be restless in the evenings or severe resulting in rhythmical screaming attacks lasting a few minutes at a time, alternating with equally long quiet periods in which the child almost goes to sleep, before another attack starts. Attacks appear to be more common in the early evening, giving rise to the name 6.00pm colic. However, normal infant crying and the crying in colic both peak in the late afternoon and early evening and is therefore of limited value. The infant will be healthy and thriving.

Conditions to eliminate

Evidence base for over-the-counter medication

Parents should be reassured that the child’s symptoms will subside over time, that their baby is well and they are not doing something wrong. Most parents will want to buy some form of medical treatment. Treatments include simeticone, lactase enzymes, low-lactose milk formulas and gripe mixtures. None have a credible evidence base.

Simeticone is reported to have antifoaming properties, reducing surface tension and allowing easier elimination of gas from the gut by passing flatus or belching. It is widely used yet has very limited evidence of efficacy. Of three trials reported, only one found a small improvement in the number of crying attacks. This trial was small (n = 26) and suffered from methodological flaws and so results should be viewed with caution.

Practical prescribing and product selection

Prescribing information relating to dimethicone is discussed and summarised in Table 9.5; useful tips relating to colic are given in Hints and Tips Box 9.3.

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