Changes

===Ionisation===

===Ionisation===

Local anaesthetics are weak bases and so more molecules are ionised than unionised. This makes it more difficult for drugs to cross the plasma membrane. Infected tissue has a lower pH than healthy tissue, causing the ratio of ionised:unionised molecules to increase. Because of this, there is poorly cellular uptake of local anaethetics in infected tisse, as they cannot cross the cell membrane. For more about the effect of pH on drugs, see the [[Pharmacokinetics#Physiological Variables|pharmacokinetics]] page.

Local anaesthetics are weak bases and so the degree of ionisation will be greatest at low pHs. Since only unionised drug can cross the nerve sheath to enter the nerve and take effect, local anaesthetics work best in alkaline surroundings where the unionised form predominates. Infected tissue has a lower pH, increasing the proportion of ionised molecules and causing poor uptake of drug. For more about the effect of pH on drugs, see the [[Pharmacokinetics#Physiological Variables|pharmacokinetics]] page.

==Side Effects and Contraindications==

==Side Effects and Contraindications==

==Drugs in this Group==

==Drugs in this Group==