In: Nursing
Describe the importance of diluting acids and other liquids especially in the formulation of drugs.
Describe the purpose of dilution in adjusting the dose and the risks that come with it.
What are the risks that arise in hospital patients receiving an infusion of a specific drug concentration over time?
How can the appropriate conversion process of units be of use in dispensing antibiotic suspensions, especially with regards to the quantity bought and the risk of under or overdosing?
Solubility, the phenomenon of dissolution of solute in solvent to give a homogenous system, is one of the important parameters to achieve desired concentration of drug in systemic circulation for desired (anticipated) pharmacological response. Low aqueous solubility is the major problem encountered with formulation development of new chemical entities as well as for the generic development. More than 40% NCEs (new chemical entities) developed in pharmaceutical industry are practically insoluble in water. Solubility is a major challenge for formulation scientist. Any drug to be absorbed must be present in the form of solution at the site of absorption. Various techniques are used for the enhancement of the solubility of poorly soluble drugs which include physical and chemical modifications of drug and other methods like particle size reduction, crystal engineering, salt formation, solid dispersion, use of surfactant, complexation, and so forth. Selection of solubility improving method depends on drug property, site of absorption, and required dosage form characteristics.
Use of the intravenous routealso permits the experimenter to give non-contingent drugdeliveries without disturbing the subject. The major disadvantages of the intravenous route are the relatively short durations of time that a particular subject can be effectively used.
General Dosing Information
Dosing is one of the most common calculation functions that you
will perform during your career. Dosing involves a series of steps,
each of which will potentially contain some calculations for you to
do. It starts with some guidelines, usually a dosing range and from
that calculating what amount of drug the patient should receive for
each dose, and how much total drug you will thus need to fill the
patient’s prescription. Let’s look at each step.
1. Locate dosing guidelines. You decide that you need to calculate
a patient-specific dose. You must first locate some dosing
guidelines. You will find these guidelines in many common texts,
and later on in your pharmaceutics, pharmacology, and therapeutics
courses. Dosing guidelines will usually give you a range to choose
from. Some of these ranges will be total daily doses. For instance
the pediatric guidelines for dosing amoxicillin, an antibiotic, for
an ear infection, are 30-50 mg/kg/day, with the total daily dose
given as three separate doses during the day. Other ranges will be
per-dose. The adult dosing guidelines for gentamicin (an
antibiotic), for instance are 1.5-2.0 mg/kg/dose with doses
commonly given every 8 hours. Cyclophosphamide, a medication given
to cancer patients,
2
can be dosed at 400-600 mg/m hopefully you get the idea.
, using body surface area to create a patient-specific dose. The
list could go on, but
2. Obtain patient variable data, such as weight. After locating the
dosing guidelines, you need to determine the value of the variable
that the dose is dependent on: most commonly the patient’s weight,
age, height, or kidney function. Determining this may involve some
detective work - you may have to ask the patient for his or her
weight, for instance, or you may need to obtain a blood
concentration of a substance (creatinine, a muscle breakdown
product) in order to determine kidney function.
3. Determine the patient-specific daily dosing range. Once you have
your dosing guidelines and the value, you will likely have to
multiply one by the other in order to get the dosing range for that
individual patient. For instance, if you have a 20 kg child who is
to receive amoxicillin, and you know that the dosing guidelines are
30-50 mg/kg/day, it is a simple matter to determine that this
patient should receive between 600 and 1000 mg of amoxicillin
daily.
4. Calculate the range for each patient-specific dose. If you have
a daily dosing guideline, and the patient is to receive more than
one dose per day, you will need to divide the total daily dose by
the number of doses/day. For instance, the patient who is to
receive between 600 and 1000mg of amoxicillin per day is to have
this medication divided evenly into three doses/day. This means
that the patient should receive 200mg to 333mg in each dose.
What do you do when you have no choice but to round up or down out
of the dosing range? In general, with an antibiotic it is better to
round up than down. With all other medications it may be better to
round down, rather than up, although if you’re just rounding up a
little bit (10% or less), then you’re probably OK rounding
up.
5. Determine an appropriate dosage form for the patient. Sometimes
you will be given a dose of a drug that a patient is receiving in
one form and will be asked to convert it to the dose a patient
should receive in another form. For example, if a patient is
receiving a drug intravenously, he or she may need to have an oral
dose calculated in order to be eligible for discharge from the
hospital. You will need to find some dose equivalency information
in order to do this.
At other time, you may initiate a change of dosage form yourself.
Physicians may write for oral suspensions for children, but some
children will prefer to take tablets. If the patient is a child
older than 5 years of age, it is best to ask him or her whether or
not he or she can swallow a tablet or would prefer liquid.
Likewise, a physician may write a prescription for a particularly
large dosage form for an elderly adult. If that patient has an
impaired ability to swallow, for example if they’ve had a stroke,
then he or she may need an alternative dosage form. Let the patient
or caregiver guide you in your choice of dosage form whenever
possible.
6. Choose an appropriate strength or concentration. Once you know
the range for each dose, it is simply a matter of examining the
strengths that a drug is available in and choosing one that is as
simple as possible for the patient to us