Syrup: sugar that does a job
A syrup is a concentrated, viscous aqueous solution of sugar — classically about 85% w/v sucrose, which is close to saturation. That high sugar level is not only there to taste sweet. At near-saturation the syrup is self-preserving: there is so little free water available that microbes struggle to grow, so a simple syrup needs little or no added preservative. The sugar also raises viscosity, giving the medicine a pleasant body and a soothing coating feel — handy in a cough linctus.
Elixir: when you need alcohol
An elixir is a clear, sweetened, hydroalcoholic solution meant to be swallowed. The alcohol is doing the cosolvent work from the last guide: it dissolves drugs and flavours that water cannot. The trade-off is that an elixir is usually less sweet and less viscous than a syrup (sugar is less soluble in alcohol), and the alcohol content limits its use in children and some patients. Choose an elixir when the active or its flavour oils simply will not dissolve in a sugar-water vehicle.
Winning the taste battle
A medicine that tastes terrible is a medicine that gets spat out — taste is a patient compliance issue, not a luxury. Two tools work together. A sweetening agent raises overall pleasantness and masks bitterness, while a flavouring agent adds an aroma the brain trusts. Bitter and salty notes are the hardest to hide; cherry, citrus and mint flavours are popular because their boldness covers a lot.
- Identify the off-taste — is it bitter, salty, or metallic? Match the flavour to the problem (citrus for sour-bitter, mint for cooling).
- Sweeten first to lift the baseline, then layer flavour on top; taste them in combination, not alone.
- Check the sweetener is compatible: high sugar may also help self-preservation, but a sugar-free sweetener will need a separate preservative.