Ectoparasiticides. Ectoparasiticides include: 1. Permethrin 2. Lindane (Hexachlorocyclohexane) 3. Crotamiton 4. Sulfur & Malathion.

Transcription

1 Ectoparasiticides Drugs used to treat scabies )الجرب) and lice infestations (pediculosis,()القمل) they usually occur due to poor hygiene and they are easy to treat. Ectoparasiticides include: 1. Permethrin 2. Lindane (Hexachlorocyclohexane) 3. Crotamiton 4. Sulfur & Malathion Permethrin: Toxic to Pediculus humanus, Pthirus pubis, and Sarcoptes scabiei. Residual drug persists up to 10 days following application. Permethrin 1% cream rinse is applied undiluted to affected areas of pediculosis for 10 minutes and then rinsed off with warm water (cream rinse means a cream that is washed after application). For the treatment of scabies, a single application of 5% cream is applied to the body from the neck down, left on for 8-12 hours, and then washed off. Lindane (Hexachlorocyclohexane): Lindane is available as a shampoo or lotion, 10% of a dose applied to the forearm is absorbed and concentrated in fatty tissues, including the brain (cause neurotoxicity). For pediculosis capitis or pubis, 30 ml of shampoo is applied to dry hair on the scalp or genital area for 4 minutes and then rinsed off. No additional application is indicated unless living lice are present 1 week after treatment. In scabies a single application is applied to the entire body from the neck down, left on for 8-12 hours, and then washed off. Patients should be retreated only if active mites can be demonstrated, and never within 1 week of initial treatment due to neurotoxicity. Crotamiton A scabicide with some antipruritic properties. Available as cream and lotion. For scabies two applications are applied from the chin down at 24-hour intervals, with a cleansing bath 48 hrs after the last application. Can be used as an alternative to lindane. Sulfur & Malathion: (safe drug) Sulfur remains a possible alternative drug for use in infants and pregnant women. The usual formulation is 5% precipitated sulfur in petrolatum. Malathion is available as a 0.5% lotion that should be applied to the hair when dry; 4-6 hours later, the hair is combed to remove nits and lice.

2 Agents Affecting Pigmentation Hydroquinone, Mequinol and Monobenzone reduce hyperpigmentation of the skin. These compounds inhibit tyrosinase, interfering with the biosynthesis of melanin leading to hypopigmentation of the skin. Topical hydroquinone & mequinol result in temporary lightening, but monobenzone causes irreversible Depigmentation. Monobenzone may cause hypopigmentation at sites distant from the area of application. Drugs that reduce hypopigmentation: Trioxsalen and Methoxsalen are psoralens used for the repigmentation of depigmented macules of vitiligo (a disease in which melanocytes are destroyed in certain areas,leading to loss of skin color). Psoralens must be photoactivated by longwave-length ultraviolet light in the range of nm (UVA) to produce a beneficial effect. The risks of psoralen photochemotherapy are cataracts and skin cancer Sunscreens: Exposure to sun leading to tanning and redness especially after swimming. Topical medications against sunlight include: Sunscreens: Contain chemical compounds that absorb ultraviolet light. Sunshades: Contain opaque materials such as titanium dioxide that reflect light. Three classes of compounds used in sunscreens: 1. p-aminobenzoic acid (PABA) and its esters. 2. The benzophenones. 3. The dibenzoylmethanes. Sunscreens are designed to absorb ultraviolet B (UVB) wavelength (from 280 to 320 nm) UVB is the range responsible for most of the erythema and tanning associated with sun exposure. The severity of skin damage depends on the duration of exposure and the time of exposure to the sun. Chronic exposure to light in this range induces aging of the skin and photocarcinogenesis. Para-aminobenzoic acid and its esters are the most effective available absorbers in the B region. The benzophenones include oxybenzone, dioxybenzone, and sulisobenzone. The benzophenones absorb from 250 to 360 nm, but their effectiveness in the UVB erythema is less than that of PABA. The dibenzoylmethanes include Parasol and Eusolex, The dibenzoylmethanes absorb wavelengths throughout the ultraviolet A range (320 to 400 nm), with maximum absorption at 360 nm.

3 Patients sensitive to UVA include: those with cutaneous lupus erythematosus and drug induced photosensitivity. In these patients, dibenzoylmethane containing sunscreen may provide improved photoprotection. The sun protection factor (SPF) of a given sunscreen is a measure of its effectiveness in absorbing erythrogenic ultraviolet light. It is determined by measuring the minimal Erythema (redness) dose with and without the sunscreen in a group of normal people. The ratio of the minimal erythema dose with sunscreen to the minimal erythema dose without sunscreen is the SPF. Fair-skinned individuals who sunburn easily are advised to use a product with an SPF of 15 or greater. (Usually erythema develops after 10 minutes of direct sun exposure, SPF= 15 means that erythema will develop after 150 minutes (93% protection), if SPF= 30 erythema develops after 300 minutes (97% protection). Drugs in leishmaniasis: Leishmaniasis is a disease caused by parasites of the Leishmania type. It spreads by the bite of certain types of sandflies, it can be transmitted from person to another). Three major forms: 1. Cutaneous (the most common; skin ulcers). 2. Mucocutaneous (ulcers of the skin, nose, mouth and throat). 3. Visceral leishmaniasis (also known as kala azar), starts with skin ulcers and then later presents with fever, anemia and enlarged spleen and liver, if untreated leads to death. -Leishmaniasis is diagnosed by the presence of parasite in biopsy from skin. -Treatment is limited due to toxicities & failure of drugs -Sodium stibogluconate (1 st line therapy) :Primary drug for all forms of the disease. -Cutaneous lesions can also be treated by fluconazole and metronidazole -Mucocutaneous and visceral disease = amphotericin B (2nd line therapy) (amphotericin B is an antifungal drug and it is effective in treatment of leishmanial diseases in case of resistance to sodium stibogluconate ) Sodium Stibogluconate - Pentavalent antimonial - Considered as first line agent for all forms of leishmaniasis. - Mechanism of action is unknown (Possible inhibition of parasite glycolysis at the phosphofructokinase reaction)

4 - Administered parenterally in a dose of 20mg/kg/day by slow IM or slow IV infusion for 20 days for cutaneous leishmaniasis and 28 days for visceral and mucocutaneous disease. - Rapidly excreted by the kidney (little metabolism) Side effects to Sodium Stibogluconate: - Pain at the injection site - Gastrointestinal upset - Cardiotoxicity, bradycardia, hypotension - Myalgia, arthralgia - Fever, Cough, &Headache - Pancreatitis - Hemolytic anemia - Resistance is frequent Pentamidine isethionate: - An alternative to sodium stibogluconate for the treatment of visceral leishmaniasis and sometimes used for cutaneous lesion. - Mechanism of action is unclear (possible inhibition of folic acid, DNA & RNA synthesis). - Given IM - Also effective in the management of pneumocystis Pneumonia (fungal infection) and trypanosomiasis (parasitic infection). Side effects to pentamidine: - Painful injection - Tachycardia, hypotension, dizziness - Dyspnea, GIT upset - Kidney, liver and pancreatic toxicity (Frequent hypoglycemia) Amphotericin B - An antifungal drug which can be used as an alternative therapy for mucocutaneous & visceral leishmaniasis resistant to sodium stibogluconate. - Ineffective orally, given IV - Toxic drug (nephrotoxicity)

5 Miltefosine - An alkylphosphocholine analog - First orally effective drug used in the treatment of visceral leishmaniasis - Side effects include vomiting, diarrhea - Elevation in liver enzymes and teratogenicity Drugs in leprosy (not common) -Leprosy is a chronic, progressive bacterial infection caused by the bacterium Mycobacterium leprae. -Symptoms that develop include granulomas of the nerves, respiratory tract, skin, and eyes. -Prolong treatment, emergence of resistance, drug toxicity and compliance represent major problems. Dapsone - A sulphone related to sulfonamides - Bacteriostatic, acts through inhibition of bacterial folate synthesis - Given orally, well absorbed and widely distributed. - Produces ten times more concentration in diseased skin than in normal skin - Side effects include Haemolysis in G6PD deficient,anorexia, nausea, vomiting, fever, allergic dermatitis Clofazimine -A phenazine dye interferes with template function of DNA (intercalating bacterial DNA). -Has anti-inflammatory activity and useful in patients in whom dapsone causes drug reactions. -Related to the fact that it is a dye, the most prominent untoward effect is red-brown to black skin discoloration. Rifampicin - Anti tubercular antilepromatous drug - Bactericidal - Used in MDT (Multi Drug Therapy) at a dose of 600mg once a month - Side effects include reddish discoloration of urine & secretions(sweat..), breathlessness, shock, collapse, pruritis, rash Other drugs: Fluoroquinolones (ofloxacin, moxifloxacin, sparfloxacin), Minocycline, Clarithromycin Currently multi drug therapy is advised to prevent the emergence of resistance, to reduce the duration of therapy, to eliminate dormant forms & to improve compliance.

6 WHO recent recommended therapy to counteract resistant: ROM therapy (Rifampicin 600 mg, Ofloxacin 400 mg, and Minocycline 100 mg therapy was recommended for cure ).