Prescribing by other routes Flashcards
Route dependent on…? (6)
- Bioavailability (or for local effects)
- Desired peak-trough levels
- Continuous / long-term release
- Availability of routes (and tolerability)
- Contraindications
- Risks (and benefits)
Bioavailability of IV
100%
How does vancomycin exert its effect?
By having concentrations constantly maintained above
the minimum inhibitory concentration (time-dependent
killing), so better with regular, smaller doses.
How does gentamicin exert its effect?
Aminoglycosides (such as gentamicin) require peak
concentrations (concentration-dependent killing), but
low therapeutic index, so better with increased dosing
interval.
Infusions - if high concentration / low volume, should be delivered by…?
Syringe pump
Sometimes infusions require significant dilution. Give an example.
E.g. if amiodarone is given peripherally
A 18-year old man with epilepsy is currently an inpatient due to worsening control of his generalised tonic-clonic seizures.
PMH Epilepsy
DH Sodium valproate 500 mg orally 8-hrly.
He weighs 70kg.
While on the ward, he is having ongoing tonic-clonic seizures for the last 5 minutes.
He already has intravenous access sited prior to his seizure.
A Phenytoin 1.4g slow intravenous injection B Lorazepam 4mg intravenously C Diazepam 10mg intramuscularly D Diazepam 10mg rectally E Midazolam 10mg bucally
B Lorazepam 4mg intravenously
A 34-year old woman is brought to Accident and Emergency with reduced consciousness. Her partner informs you then she has been injecting heroin.
PMH Intravenous drug use - mixed substances.
DH None.
She weighs 50kg.
Following initial treatment by the ambulance services with naloxone 400 micrograms intravenously, she has improved (initial GCS 6/15). She has managed to remove her nasopharyngeal airway.
She still has intravenous access.
Examination
RR 12, Sats 96% on 28% O2 by venturi mask. Airway selfmaintained.
BP 126/68, pulse 68 regular.
GCS 14/15, no lateralising signs
There are concerns that she is about to abscond from the hospital.
A Diazepam 2.5mg orally B Lorazepam 1mg intravenously C Naloxone 400 micrograms intramuscularly D Naloxone 400 micrograms intravenously E Naloxone 400 micrograms subcutaneously
C Naloxone 400 micrograms intramuscularly
A depot intramuscularly may be helpful to prevent her opiate toxicity to return once the intravenous naloxone wears off – particularly if she has left the hospital
environment.
Subcutaneous naloxone can also be an alternative to intravenous delivery when there is no intravenous access.
A 83-year old woman is brought to Accident and Emergency, found by her carers in the morning (8AM), in bed, with weakness in her right face, arm and leg. She was well last night (10PM).
PMH Dementia, osteoarthritis.
DH. Paracetamol 1g as required (maximum 6-hrly).
SH. Lives in residential home, carers three time a
day, mobilises less than 20 yards with roller frame.
Examination
Dense right sided weakness. Unsafe swallow.
Due to the timing of her stroke, she is not a candidate for thrombolysis. She does not have a nasogastric tube in place as due to her resistance, it was not safely sited.
A Aspirin 300mg intramuscularly B Aspirin 300mg intravenously C Aspirin 300mg orally D Aspirin 300mg rectally E Aspirin 300mg subcutaneously
D Aspirin 300mg rectally
Subcutaneous infusion - commonly used in…?
Low or high volume?
Give some examples.
Low-volume (e.g. 48ml/24hr)
Commonly used in palliative care
E.g. hyocine butylbromide / hydrobromide,
midazolam, metoclopramide…
Subcutaneous pellets - what does this allow? Give an example.
Allows slow-release
E.g. oestradiol
Subcutaneous insulin formulations - human insulin are ______ at low concentrations. Aggregates into stable dimers at… (3). Forms hexamers…
monomers
higher concentrations
lower pH (2-8)
in presence of protamine
in presence of Zn2+ ions
Insulin analogues -give some examples.
E.g. Lyspro and Aspart; Glargine
What temp must long-term supplies of insulin be kept at?
Long-term supplies must be kept at 2-8C (or chemically
destabilised)
Intramuscular - small volumes.
Entry into systemic circulation - fast/slow?
Dependent on…?
Fast entry
Blood flow dependent
