This section is concerned with interactions where effects of anaesthetics (both general and local) and neuromuscular blocking drugs are affected by presence of other drugs. Where anaesthetics or neuromuscular blocking drugs are responsible for an interaction they are dealt with under heading of drug affected
Many patients undergoing anaesthesia may be taking long-term medication,which may affect their haemodynamic status during anaesthesia. This section is limited to drug interactions and therefore does not cover many precautions relating to patients taking long-term medication and undergoing anaesthesia in general (for example, drugs affecting coagulation).
In general anaesthesia a balanced approach is often used to meet main goals of anaesthetic procedure. These goals are unconsciousness/amnesia,analgesia, muscle relaxation, and maintenance of homoeostasis. Therefore general anaesthesia often involves use of several drugs, including benzodiazepines, opioids, and anticholinesterases, as well as general anaesthetics (sometimes more than one) and neuromuscular blockers. The use of several different types of drugs in anaesthesia means that there is considerable potential for drug interactions to occur in peri-operative period, but this section is limited to effects of drugs on general anaesthetics and neuromuscular blockers. The interactions of drugs affecting these other drugs used in anaesthesia are covered in other sections (anticholinesterases,, benzodiazepines, , and opioids, ).
There may be difficulty in establishing which of drugs being used in a complex regimen are involved in a suspected interaction. It should also be borne in mind that disease processes and procedure for which anaesthesia is used may also be factors to be taken into account when evaluating a possible interaction
Some established interactions are advantageous and are employed clinically. For example, hypnotic and anaesthetic effects of propofol and midazolam’, , are found to be greater than expected additive effects and this synergy allows for lower dosage regimens in practice. Similarly nitrous oxide reduces required dose of inhalational general anaesthetics (see ‘Anaesthetics, general + Anaesthetics, general). Anticholinesterases oppose actions of competitive neuromuscular blockers, and are used to restore muscular activity after surgery (see Neuromuscular blockers + Anticholinesterases interaction).
The general anaesthetics mentioned in this section are listed in table 1 below,. Barbiturates used as anaesthetics (e.g. thiopental) are largely covered here,whereas those used predominantly for their antiepileptic or sedative properties (e.g. phenobarbital or secobarbital) are dealt with in appropriate sections.
The competitive (non-depolarising) neuromuscular blockers and depolarising neuromuscular blockers mentioned in this section are listed in table 2 below’,. The modes of action of two types of neuromuscular blocker are discussed in monograph ‘Neuromuscular blockers + Neuromuscular blockers. It should be noted that mivacurium (a competitive blocker) and suxamethonium (a depolarising blocker) are hydrolysed by cholinesterase,so share some interactions in common that are not relevant to other competitive neuromuscular blockers.
The local anaesthetics mentioned in this section are listed in table 1 below,. The interactions discussed in this section mainly involve interaction of drugs with local anaesthetics used for epidural or spinal anaesthesia. The interactions of lidocaine used as an antiarrhythmic is dealt with in Antiarrhythmics,.
| Table 1 Anaesthetics | |||
|---|---|---|---|
| General anaesthetics | |||
| Halogenated inhalational anaesthetics | Miscellaneous inhalational anaesthetics | Barbiturate parenteral anaesthetics | Miscellaneous parenteral anaesthetics |
| Chloroform | Anaesthetic ether | Methohexital | Alfadolone |
| Desflurane | Cyclopropane | Thiamylal | Alfaxolone |
| Enflurane | Nitrous oxide | Thiopental | Etomidate |
| Halothane | Xenon | Ketamine | |
| Isoflurane | Propofol | ||
| Methoxyflurane | |||
| Sevoflurane | |||
| Trichloroethylene | |||
| Local anaesthetics | |||
| Amide-type | Ester-type (ester of benzoic acid) | Ester-type (ester of para-aminobenzoic acid) | |
| Articaine | Cocaine | Chloroprocaine | |
| Bupivacaine | Procaine | ||
| Etidocaine | Propoxycaine | ||
| Levobupivacaine | Tetracaine | ||
| Lidocaine | |||
| Mepivacaine | |||
| Prilocaine | |||
| Ropivacaine | |||
| Table 2 Neuromuscular blockers | ||
| Competitive (Non-depolarising) blockers – Aminosteroid type | Competitive (Non-depolarising) blockers – Benzylisoquinolinium type | Depolarising blockers |
| Pancuronium | Alcuronium | Decamethonium |
| Pipecuronium | Atracurium | Suxamethonium (Succinylcholine) |
| Rapacuronium | Cisatracurium | |
| Rocuronium | Doxacurium | |
| Vecuronium | Gallamine | |
| Metocurine | ||
| Mivacurium | ||
| Tubocurarine (d-Tubocurarine) |
| Table 3 Anaesthetics | |||
|---|---|---|---|
| General anaesthetics | |||
| Halogenated inhalational anaesthetics | Miscellaneous inhalational anaesthetics | Barbiturate parenteral anaesthetics | Miscellaneous parenteral anaesthetics |
| Chloroform | Anaesthetic ether | Methohexital | Alfadolone |
| Desflurane | Cyclopropane | Thiamylal | Alfaxolone |
| Enflurane | Nitrous oxide | Thiopental | Etomidate |
| Halothane | Xenon | Ketamine | |
| Isoflurane | Propofol | ||
| Methoxyflurane | |||
| Sevoflurane | |||
| Trichloroethylene | |||
| Local anaesthetics | |||
| Amide-type | Ester-type (ester of benzoic acid) | Ester-type (ester of para-aminobenzoic acid) | |
| Articaine | Cocaine | Chloroprocaine | |
| Bupivacaine | Procaine | ||
| Etidocaine | Propoxycaine | ||
| Levobupivacaine | Tetracaine | ||
| Lidocaine | |||
| Mepivacaine | |||
| Prilocaine | |||
| Ropivacaine | |||