Week 7

Pharmaceutical preparations & concentrations

As a pharmacy technician, you need to understand the concept of concentration related to pharmaceutical preparations.

Pharmaceutical preparations consist of:

• Ingredients = active and inactive substances, often a solid.
• A vehicle = a substance that helps deliver the active ingredients to the desired site of action, usually a liquid.

In pharmacy, when we are compounding, we are combining specific amounts of ingredients with a specific amount of a vehicle to make a pharmaceutical preparation to meet the needs of our patients. For example, the doctor has prescribed omeprazole suspension for a patient who has difficulty swallowing capsules. In this situation, we would combine omeprazole powder (active ingredient) and sodium bicarbonate powder (inactive ingredient) with water (vehicle) to make a suspension that the patient can easily swallow.

When we make a pharmaceutical preparation such as the omeprazole suspension in the example above, it is crucial that we follow the SOPs for compounding and the instructions for the specific preparation. This includes selecting, calculating, measuring, and mixing the right amounts of ingredients and vehicles. If we do not do this, the patient is put at risk of serious harm.

• They would not get the desired effect and treatment for their health concern.
• They may experience adverse reactions.
• There is a potential for an overdose.
• The stability and effectiveness of the preparation are impacted, making it ineffective.
• The taste and texture are not acceptable, so the patient won’t want to take it.

In pharmacy, concentration is an expression of the ratio of the amount of an ingredient to the amount of product. It is written in fraction form, where the letter ‘w’ refers to a weight and the letter ‘v’ refers to a volume.

w	weight
v	volume

We will now take a look at some examples of concentrations of pharmaceutical preparations.

w/v:  In the case of a solid ingredient in a liquid vehicle, the ratio is expressed as weight per volume or w/v. Example: Pamol ® suspension. Our solid ingredient is paracetamol, measured in weight (mg), and our liquid ingredient is an orange-flavoured syrup measured in volume (ml).
v/w: If a liquid ingredient is formulated into a solid vehicle, the ratio is expressed as v/w. Example: 10% Glycerol in non-ionic cream. In this example, the glycerol is the liquid ingredient measured in volume. The non-ionic cream is considered the solid ingredient because it is measured in weight.
v/v: If both drug and vehicle are liquids, it is expressed as v/v. Example: Xerostom® mouth spray. In this example, the drug pilocarpine (generic name) is the liquid ingredient measured in volume, in a liquid ingredient (a mixture of different types of oils and liquids). Both ingredients are measured in volume.
w/w: If both the drug and the vehicle are solid in nature, the ratio is expressed as w/w. Example: 0.5% Hydrocortisone in Cetomacrogol cream. In this example, the hydrocortisone is the solid ingredient measured in weight, and the cetomacrogol cream is also the solid ingredient measured in weight.

You will be required to calculate the correct quantity of medicine to dispense for each prescription to ensure the patient receives an adequate supply to last for the duration of their prescribed treatment.

You may also be asked to calculate a dose and the quantity to dispense based on body weight. For example:

• A young patient who weighs 9kg is prescribed Ibuprofen 100mg/5ml suspension. The prescription states the patient is to have 7.5mg/kg tds for 1/12.

To work this out, we will start by asking ourselves: what is the dose in ml that the patient requires?:

• 7.5mg x 9kg = 67.5mg
• We want: 67.5mg in xml
• We have: 100mg in 5ml

Therefore, our calculation will look like this:

Now that we know these numbers, we can move on to the second part, which is finding out the quantity to dispense.

• We know that tds means three times per day.
• We know that 1/12 means 30 days.

Therefore, our calculation will look like this:

• 3 x 3.375 x 30 = 303.75ml to be dispensed

Calculate the answers for the following. You will find out if you are right immediately, and the activity will automatically progress through all five questions.

Let’s now move on to another scenario where you are required to calculate the total quantity required to dispense.

Self-directed learning activities:

Take the following seven-question quiz to ensure you can perform the required calculations.

Excellent job! You completed this week's learning of Professional Practice!

Cautionary and advisory labels

The Pharmaceutical Society of NZ’s (PSNZ) Cautionary and Advisory Labels (CALs) have an important role to play. Given its name, take a moment to consider what you think that might involve.

CAL's role is to oversee additional label information placed on medicine to:

• prompt counselling of customers on specific advice
• prevent or reduce adverse reactions
• warn of important side effects
• ensure the medicine is taken in the most effective manner
• meet the professional and legal obligations regarding medicines information.

Can you think of any medicine warning labels you see regularly as a consumer?

The professional and legal obligation to provide CALs are contained in the following documents:

• Pharmacy Council Code of Ethics 2011
• Code of Health and Disability Services Consumer Rights 1996.

CALs may be a separate brightly coloured label (recommended by the PSNZ) or abbreviated forms of the CALs can be printed on the dispensing label.

When attaching CALs, it is important that they are placed so that they do not cover up the main label directions. Generally, they should be used regardless of whether an abbreviated version of the label is included in the main label.

A prescriber who, for any reason, does not wish a Cautionary and Advisory Label to be used in a particular case should endorse the prescription with ‘N.C.L’, which stands for ‘No Cautionary Label’.

When a patient or their representative collects a prescription that has a CAL attached, it is important that the person handing over the prescription ensures the CAL information is pointed out and explained verbally.

For each of the CALs listed below, click on each label or (+) symbol to read the full advice and information:

*Note: There is no Label 12.

As well as CALs, there are also dispensing label references that can be added to the labels as appropriate. These are:

• Ref A: swallow whole; do not crush or chew
• Ref B: with food
• *Ref D: until the medicine is finished

*Note: There is no reference C.

 

You've just taken a lot of information on board, so have some fun and check your knowledge by answering the next ten questions about CALs. Don't worry if you don't get them all correct. Just make sure to note down the correct answer so that you can remember it going forward. Have fun!

Another week of Introduction to Dispensing is complete. Well done.

Pain

Each kind of pain medicine has benefits and risks. Some types of pain respond better to one kind of medicine than to another kind. As we know, pain is felt differently for each person, and what works for one person’s pain may not work for someone else.

Take a moment to study and learn the terms in the completed activity.

OTC pain-relieving medicines work by reducing the effect of a chemical called prostaglandin. Prostaglandins act as chemical signals that control different processes in the body, including the transmission of pain signals to the brain and signals to the body to cause inflammation and fever—reducing or blocking the effects of prostaglandins results in the relief of pain, inflammation, and fever.

Paracetamol

Paracetamol is used to treat mild to moderate pain. It is thought to work by blocking prostaglandins from transmitting pain signals from the nerves in the spinal cord up to the brain.

Answer these three questions about paracetamol.

Paracetamol overdose can occur accidentally or in the context of self-harm. As a result of paracetamol being metabolised (processed) in the liver, a small amount of a toxic compound is formed, but the liver is able to detoxify this quickly. In an overdose, the liver cannot keep up with the amount of detoxification needed, which results in a build-up of the toxic compound. The build-up damages the liver and causes it to fail. It can take several days for the effect of a paracetamol overdose to be felt, by which stage it is too late to treat the overdose, and the person will die.

Alcoholism and heavy drinking damage the liver and its ability to function. Therefore, these people, along with those who have impaired liver function for other reasons, are at risk of a paracetamol overdose due to the liver not being able to metabolise it.

Ibuprofen

Ibuprofen is used to reduce mild-to-moderate pain and inflammation. It works by stopping the damaged or infected body tissues from producing prostaglandins.

Answer these questions about ibuprofen.

As with Paracetamol, an overdose of Ibuprofen may not be felt right away. Mild symptoms include ringing in the ears, GI disturbances, rash, blurred vision, and sweating. Severe symptoms include low blood pressure, difficulty swallowing, severe headaches, seizures, and coma.

Headache

Headaches are very common. There is a wide variation in the type of pain you could experience with a headache and how long it may last. Headaches can be broken into two categories:

• Primary - No clear cause, such as migraines
• Secondary - Have a clear cause, such as headache from an illness

Headache: treatment and advice

⚠When to refer to the pharmacist

When assessing a customer with a headache, you need to be alert to any headache warning signs and indications for referral to the pharmacist.

Warning signs

• The first headache in a person over 50
• Headaches that are brought on by:
  • lying down
  • cough
  • specific activities.
• Headaches described as:
  • “The worst headache of my life.”
  • New or different to previous headaches
  • Severe right from the start
  • Develop after a head injury or trauma
  • Worsen over time (months).
• Headaches with other symptoms, such as:
  • High blood pressure
  • Muscle aches
  • Weight loss
  • Changes in consciousness
  • Confusion
  • Gait disturbances
  • Loss of balance
  • Memory loss
  • Seizures
  • Speech difficulties.

Other signs

• The customer also has a fever, rash, or stiff neck.
• The symptoms have lasted longer than 24 hours.
• The customer is aged less than 12 years old.
• Older people experiencing reoccurring headaches that come from the temples.
• The customer has headaches occurring more than once a month.
• When a customer is attempting to purchase large quantities of analgesics.
• Symptoms have persisted despite treatment with adequate doses of pain relievers.
• The customer is taking medications, including complementary medicines.
• The customer is pregnant or breastfeeding.
• The customer has other health conditions.
• The customer has allergies to medicines.

Period pain

Experiencing painful periods is called Dysmenorrhoea. (‘dys’ from the word bad and ‘menorrhoea’ from the word menstruation).

Dysmenorrhoea is divided into two types:

Primary	Pain without an underlying problem. It is common and affects more than half of all women at some stage.
Secondary	Pain with an underlying cause, such as endometriosis.

Common signs and symptoms of dysmenorrhoea include:

• lower abdominal cramps that can be mild to severe
• headache and ache in the back extending to the thighs
• nausea and vomiting
• constipation
• diarrhoea
• breast tenderness or pain
• fatigue.

Dysmenorrhoea: treatment and advice

In this week's SDL, we’ll look at the appropriate treatment and advice for this type of pain.

⚠When to refer to the pharmacist

• When the customer is over 30 and experiencing period pains for the first time.
• Very heavy menstrual bleeding- changing pad or tampon every 1-2 hours.
• If pregnant or postmenopausal and has vaginal bleeding.
• Has an intrauterine device (IUD).
• Pain persists beyond the first two days of period.
• If there is fever and vomiting at the same time.
• NSAIDs are not fully effective.
• Pain is described as severe or distressing.
• Abnormal discharge or bleeding between periods.
• Pain unrelated to menstruation or during intercourse.
• Pain is worse with each period.
• the customer is taking medications, including complementary medicines.
• the customer has other health conditions.
• the customer has allergies to medicines.

That wraps up another week of study. Ka pai - good work!