Calculations Flashcards
1% means
either
- 1g in 100mL (or 10mg in 1mL) for weight/volume calculations
- 1g in 100g for weight/weight calculations
how many mg are in 1 mL of 1% lidocaine solution
10mg
i.e. if there is 1g in 100ml, in 1mL there is 0.01g (/1000) or 10mg
in a 2% solution there is
2g in 100mL
2mg in 10mL
express 250micrograms/ml as a percentage
you already know that 1% is equivalent to 1g in 100mL- can use this as a reference point
* 250 micrograms/ mL = 0.25 mg/mL
* 0.25 mg/mL= 25 mg/100mL (this does not mean 25%)
* 25mg/100mL = 0.025 g/ 100mL = 0.025%
an adult male patient is given an IM injection of 0.5mg of adrenaline 1 in 1000 for treatment of anaphylaxis. What volume of solution should be given?
0.5 mL
1.1 in 1000= 1g in 1000ml = 1000mg/1000ml = 1mg/ml = 0.5mg/0.5ml
therefore to get 0.5mg of adrenline, will need 0.5mL of 1 in 1000 adrenline
you decide to inititate a treatment dose of enoxaparin at a dose of 1.5mg/kg (or150 units/kg). What dose do you give? Express in both mg and units
75mg or 7500 units
you are asked to re-prescribe a gentamicin for a 65kg patient. Blood results are as follows:
- 63mL/min
- Gentamicin serum concentration = 6.2 micrograms/mL
- Time since last dose (h)= 10
You are using a 7mg/kg regime.
Use the nomogram above to select a suitable dose and dosing interval
455mg every 36 hours
how much NaCL 0.9% would you need to add to an ampoule of hydralazine 20mg/2ml make it 1mg/ml?
hydralazine is presented as 20mg/2ml. Adding 18mL of NaCL 0.9% would therefore reuslt in a conc of 1mg/mL
a neurosurgical patient is prescribed phenytoin 300mg daily, which is being given in capsule form. A few days after her operation, she complains of difficulty swallowing the capsules and the nurse asks you if you can re-prescribe phenytoin in liquid form.
Phenytoin is available as a liquid, but it contains phenyotin base rather than the sodium salt of phenytoin found in the capsules.
What dose of liquid phenytoin should you prescribe
LOOK on the BNF: Dose equivalence and conversion
- 100mg administered as a capsule is equivalent in therapeutic effect as approx 92mg administered as a liquid
calculations: (92/100) X 300= 276mg
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