Lotions and Liniments: The Practical

Definitions

Both are for external use only.

Lotions

Lotions can be:

• solutions, for example an antiseptic lotion;
• suspensions, for example calamine lotion, in which solids are spread through water;
• emulsions, for example some moisturising lotions.

They are used to cool, soothe, protect, clean or treat the skin. Lotions that contain water cool the skin as the water evaporates. Glycerol is added to some lotions to keep the skin from drying.

Calamine lotion

This is a suspension lotion. The powders (calamine and zinc oxide) are heavy and do not dissolve, so the lotion needs a suspending agent, such as bentonite, and must be shaken.

Illustrative practice formula, not a pharmacopoeial one. Use the formula your school gives you.

Calamine lotion, 100 mL: calamine 15 g, zinc oxide 5 g, bentonite 3 g, glycerol 5 mL, purified water to 100 mL.

Method

1. Sprinkle the bentonite on some of the water and leave it to swell and form a smooth mucilage.
2. Mix the calamine and zinc oxide in a mortar with the glycerol to make a smooth paste.
3. Add the bentonite mucilage gradually to the paste, stirring until smooth.
4. Transfer to a measuring cylinder, rinse the mortar and add the rinsings.
5. Make up to the final volume with purified water.
6. Put into a bottle, and label: "Shake the bottle well before use. For external use only."

Scaling example. Make 60 mL.

1. Scale factor = 60 ÷ 100 = 0.6
2. Calamine = 15 × 0.6 = 9 g
3. Zinc oxide = 5 × 0.6 = 3 g
4. Bentonite = 3 × 0.6 = 1.8 g
5. Glycerol = 5 × 0.6 = 3 mL
6. Purified water to 60 mL

Using a suspension lotion

Shake the bottle. Shake a little onto cotton wool and dab onto the skin. Do not rub. Let it dry. Use it on unbroken skin such as a rash or insect bites, as advised.

Liniments

A liniment is rubbed in. Most contain:

• an oil (such as arachis oil or olive oil), which lets the hand glide, or alcohol or water;
• one or more counter-irritants, such as methyl salicylate, camphor or menthol, which warm the area and ease pain.

Oily liniment

Illustrative practice formula.

Methyl salicylate liniment: methyl salicylate 25 mL, arachis oil to 100 mL.

Method

1. Measure the arachis oil in a dry measuring cylinder.
2. Measure the methyl salicylate in a small, dry measuring cylinder.
3. Mix them in a dry bottle or beaker, and make up to the volume with arachis oil.
4. Label.

Everything must be dry, because water does not mix with oil.

Scaling example. Make 40 mL.

• Methyl salicylate = 40 × 25 ÷ 100 = 10 mL
• Arachis oil to 40 mL, which is 30 mL of oil

Safety with liniments

• For external use only, and never swallowed.
• Do not apply to broken or sore skin, the eyes, the mouth or other mucous membranes.
• Do not cover with a tight bandage or heat pad, which can cause burns.
• Wash the hands after use.
• Methyl salicylate is poisonous if swallowed, even in small amounts, especially by children, so use a child-resistant closure where possible and keep out of reach.

Containers and labels

• Use a fluted (ribbed) bottle or a coloured bottle for external products, so it cannot be mistaken for medicine to be swallowed.
• Label "For external use only" in clear letters.
• Add "Shake the bottle well before use" for suspensions and emulsions.
• Give the date and discard date, directions, and the patient's name.
• Warn about fire for liniments with alcohol, because they are flammable.

Faults and what to do