Pharmacology Flashcards
What dictates the choice of vehicle
Physio-chemical properties of the drug - how hydrophobic/Phillic it is
The condition of the skin
What are topical drugs used to treat
Superficial skin disorders - eczema etc Skin infections Itching Dry skin Warts
What factors of absorption are dependent on the vehicle
The concentration of drug in the vehicle
The partition coefficient
What are excipients
Substances added to the ointment etc that enhance solubilty and absorption
Pharmacologically inert in itself
What factors improve the partitioning of a drug
Hydration of the skin by occlusion - ointment or cling film
Stops water loss
Inclusion of excipients
How does the nature of the skin influence the topical drug chosen
Site of application - thickness of stratum corneum
Hydration of the skin
Intergrity of the epidermis
What are the 4 categories of steroid in the UK
Mild
Moderate
Potent
Very potent - can only be prescribed by the dermatologist
How do you choose a topical steroid
Depends on the severity of disease and the anatomical site
What are some long term effects of high potency steroids
Steroid rebound - down regulation of receptor Skin atrophy Systemic effects Spread of infection Rosacea Stretch marks
Describe the subcutaneous route of administration
Needle is inserted just beneath the surface of the skin
Drug reaches systemic circulation by diffusion into capillaries or lymphatic system
What are the advantages of the subcutaneous route
Slow absorption
Useful for protein drugs (insulin) and oil-based drugs
Can be used to create a depot of drug that is slowly released into system
Simple and painless
What are the disadvantages of the subcutaneous route
Injection is volume limited
why is the skin a good route for drug administration
Application is simple and non sterile (for topical drugs)
Allows for steady-state plasma conc to be achieved over a long period
Avoids first pass metabolism
Drug absorption can be terminated
What is a disadvantage of the skin as an administration route
Intact skin is a water tight barrier so only some drugs can cross the epidermis
What are the advantages of topical treatment
Direct application
Reduces systemic effects
What are the disadvantages of topical treatment
Time consuming
Correct dosage can be difficult
Messy - issue with greasy preparations
What are the advantages of creams
Cooling and moisturing
Non-greasy
Easy to apply
Cosmetically acceptable
What are ointments useful for
Occlusive - retains moisture
Good for thickened plaques in psoriasis
What are lotions used for
To treat the scalp and other hair bearing areas
What are gels used to treat
Scalp
Hair bearing areas
Face
Describe pastes
Semisolid
Often contain fine powders such as ZnO
They are protective, occlusive and hydrating
Used for cooling, bandages and around ulcers
Describe foams and their use
2 or 3 phases - usually hydrophilic liquid in continuous phase with foam agent in gaseous phase
Gives increased penetrance of active agents
Can spread easily over large areas of skin
Non-greasy or oily
What are keratolytics used for
Used for treating thickened skin
Describe the use of emollients
Help rehydration of the epidermis - used for dry skin Need to apply frequently an liberally Cosmetically acceptable Can be used as a soap substitute Fire risk if contain paraffin
How do you apply emollients
Apply after bathing
Apply in direction of hair growth
Use clean spatula to remove from tub - prevents contamination
What are topical steroids commonly used for
Mainly eczema
Psoriasis
Other inflammatory dermatoses
Keloid scars
What are the side effects of topical steroids
Thinning of the skin Purpura - dark purple marks on skin Stretch marks Rosacea Fixed telangectasia Perioral dermatitis May worsen or mask infection Systemic absorption Tachyphylaxis Rebound flare
What are calcineurin inhibitors
Non-steroid anti-inflammatory - e.g. Tacrolimus Suppress lymphocyte activation Use for atopic eczema Less side effects than steroids May cause burning sensation
What are the clinical uses of antiseptics
Recurrent infections
Antibiotic resistance
Wound irrigation
One example is potassium permanganate bath
What skin conditions are antivirals used for
Herpes simplex (cold sore) - topical
Eczema herpeticum - oral
Herpes zoster - oral
Name some topical anti-fungals
Clotrimazole
Nystatin
Ketoconazole
Name some fungal skin conditions
Candida - thrush
Dermatophytes - ringworm
What conditions might you use keratolytics for
Viral warts
Hyperkeratotic eczema and psoriasis
Corns and callouses
Removing keratin plaques from scalp
How would you treat a wart
Mechanical pairing - take off Keratinolytics Formaldehyde - soak for whole foot Silver nitrate - localised Cryotherapy - localised
What is the most common adverse drug reaction
Mainly cutaneous - show up with skin symptoms
around 30% are this
What types of reaction can drugs cause
Immunologically mediated reactions - all types
Not dose dependant
Non-immunological
Can be dose-dependent
what are the typical presentations of cutaneous drug eruption
exanthematous, maculopapular rash - 75-95% of the time Urticarial - 5-10% very rarely pustular etc itch is very common usually self-limiting mucous membranes usually spared
what are the risk factors for drug eruptions
Age - very young and elderly Gender - more in females Genetics - predisposition Concomitant disease - infection Immune status - previous sensitivity Chemistry of the drug Route of administration Dose Half-life
how do drug reactions usually resolve
Often resolve when the drug treatment is stopped
how soon after taking the drugs does an eruption usually occur
onset is usually 4-21 after first taking the drug
what are some signs of a serious drug reaction
involvement of mucous membrane Facial redness and swelling Fever Pain Blisters, necrosis SOB, wheezing
How does an urticarial drug reaction occur
usually an immediate IgE reaction (type I)after 2nd drug exposure
Can be a direct release of inflammatory mediators on first exposure
describe the appearance of an urticarial rash
Dermal oedema - raised wheal
Blanches if pressure is applied
Can come and go
Which drugs can cause a bullous or pustular reaction
Glucocorticoids Androgens Antibiotics CCB Antimalarial
which drugs are associated with fixed drug eruptions
Tetracycline, doxycycline
Paracetamol
NSAIDS
Carbamazepine
Describe the presentation of a fixed drug eruptions
Well demarcated plaques Red and painful in the same place - can reoccur Often appear on hands, genitals, lips usually mild
Name some severe cutaneous drug reactions
SJS
TEN - shedding of whole body superficial layer
DRESS - huge number of circulating eosinophils
describe a phototoxic drug reaction
non-immunological reaction caused by the drug and light
Makes skin more sensitive
Can occur in a sunburn like reaction
How could a phototoxic reaction present
Immediate prickling with delayed erythema & pigmentation
Exaggerated sunburn
Exposed telangiectasia
Increased skin fragility
what drugs are associated with phototoxicity
antibiotics thiazides NSAIDs immunosuppressants Amiodarone
What investigations can be used for drug reactions
Clear history
Phototesting for phototoxic reactions
Patch and photo patch test
Skin prick tests for specific drugs
how do you manage a cutaneous drug reaction
discontinue the drug
use alternative
antihistamine may help with some symptoms
