Week 2 Flashcards
Two types of autonomic nervous system
• Sympathetic
- Neurotransmitter: Noradrenalin and adrenergic
- Receptors: Alpha and Beta
• Parasympathetic
- Neurotransmitter: Acetylcholine and Cholinergic
- Receptors: Muscarinic
Aqueous humour production:
• Transmitter : Noradrenaline
• Receptor:
- Alpha: Inhibit production
- Beta: Increase production
Agonists:
• Activate post-synaptic membrane receptors
• Mimics the action of endogenous neurotransmitters (Mimetics)
• Stimulate post-synaptic receptors (Stimulants)
• Full agonists: full activation
• Partial agonists: partial activation
• Adrenergic agonist: sympathomimetic
- Alphagan (glaucoma)
- Iopidine (glaucoma)
• Cholinergic agonist:parasympathomimetic
- Pilocarpine (myosis, pupil constriction)
What do antagonists do?
• Block or occupy post-synaptic receptors
• Reduce activity of endogenous neurotransmitters (lytic)
• Adrenergic antagonist: sympatholytic
- Timolol (beta blocker): glaucoma
• Cholinergic antagonist: parasympatholytic
- Tropicamide: cycloplegic
What are the types of Alpha and Beta receptors? And some drugs associated
• Alpha 1:
• Alpha 2: Brimodine
• Beta 1:
• Beta 2:
(Both affected by Timolol)
Definition of pharmacodynamics and pharmacokinetics
• Pharmacodynamics
The fundamental mechanisms of drug action
• Pharmacokinetics
Time-based description of drug activity
1. Administration
2. Absorption
3. Distribution
4. Metabolism
5. Excretion
What are the modes of administration?
- Oral
- Ocular
- Nasal
- Sublingual/Buccal
- Epidermal
- Rectal
- Vaginal
- Parenteral (injection, infusion implant)
- Enteral = to/through epithelium of GI tract
- Par = not. Not via the GI tract. The rest of the types, rely on the GI tract at some point.
Describe oral administration
• Drug absorbed by blood vessels of the digestive tract
• Drug must pass through liver before accessing general circulation
• First pass metabolism reduces the proportion of active drug available at the target site
What are the 4 points of antimicrobial stewardship?
• a) consider alternative options and only prescribe antimicrobials when this is clinically appropriate
• b) be aware of local guidelines on antimicrobial prescribing
• c) not issue an immediate prescription for an antimicrobial to a patient who is likely to have a self-limiting condition
• d) only issue repeat prescriptions for antimicrobials if these are needed for a particular clinical condition or indication.
Advantages of Topical NSAID
• Direct delivery to target site
• Increased availability at target receptor sites
• Improved therapeutic effect at lower doses
• Rapidity of therapeutic effect
• Significantly reduced risk of ADRs
Adverse drug reaction types - Gastric ulceration, peptic bleeding
What is the pharmacokinetics of topical ocular administration?
• Initial rapid wash-out
Tear film: 7-10ul
Eyedrop: 30-40 Ml
• Over lid margin and peri-ocular skin
• Drain through punctum
- sup/inf canaliculi
- common canaliculus
- lacrimal sac
- nasolacrimal duct
• Absorbed by nasal mucous epithelium
What is important about systemic absorption of topically applied drugs?
• Unintended absorption into systemic circulation
• No first pass metabolism; drug passes directly into systemic circulation
• Increased risk of significant ADRs
- E.g. Beta blockers (sympathetic) can cause bradycardia if absorbed systemically
Whats important about phenylepherine systemic affects?
• Agonist of sympathetic nervous, mimics iris dilator muscles, causing dilation
• Topical phenylephrine can affect systemic blood pressure
• Increases blood pressure
What can be said about topical antihistamine administration?
• No drowsiness found in older, sedating antihistamines
• Olopatadine also shows mast cell stabilising activity
Without IP?
Topical antihistamine: antazoline
Other active ingredient - xylometazoline (phenylephrine)
- needs to check Anterior chamber as dilates pupil
What is the dose response curve?
• The minimum concentration of a drug which starts to have an affect on the patient
• The saturation point; once reached, any increase in drug concentration doesnt cause affect
- Can also get toxic at high levels, i.e toxic corneal epithelium reaction
• ED50 - effect dose 50; the amount of concentration needed to produce 50% of effect.
Whats important about ED50?
• ED50 - effect dose 50; the amount of concentration needed to produce 50% of effect.
- drugs that have a low concentration for ED50 = high affinity for receptors, therefore are POTENT
- May therefore cause more ADR
What clinical implications + advice is there regarding eye drops?
- Advise patients to leave 5 minutes between eye drops
- Advocate lid closure following instillation
• 67% reduction in systemic absorption by naso-lacrimal occlusion
• 65% reduction in systemic absorption with eyelid closure - Consider viscosity
• Retention period
• Duration of contact - Consider ocular health
• Corneal epithelium
• Pseudophakia
What is drug elimination?
• Elimination requires functioning kidneys and liver
> Kidney eliminates majority of drug
> Liver transforms drug into metabolite
• Impaired elimination increases risk of ADRs
• Drugs are also excreted via breast milk
“Should not be given to women who are breast-feeding”
When should Oral Tetracycline antibiotics be avoided?
• “Should be avoided or used with caution in patients with hepatic impairment.”
• “May exacerbate renal failure and should not be given to patients with renal impairment.”
• Oral Tetracycline Antibiotics
- Doxycycline
- Minocycline
- Tetracycline
- Oxytetracycline
What kind of drug interactions are there?
• Impaired drug absorption
Tetracycline: milk, calcium, magnesium, zinc, antacids
• Effect amplification
NSAIDs with Warfarin: enhanced anticoagulant effect
• Cross hypersensitivity
Allergy to aspirin: may extend to ibuprofen and naproxen
