Medications that interact with General Anesthesia

General Anesthesia is an integral part of Oral and Maxillofacial Surgery, it consists of many components that might interact with medications taken for other health issues. General Anesthesia is administered in Dental treatments such as surgeries for Orofacial trauma Trauma such as Le-Fort fractures, Prosthetic surgeries such as Orthognathic surgery, Large Tumors (Ameloblastoma) or Cyst (Odontogenic Cysts) removals in the Mandible or Maxilla, Malignant lesions, etc. Proper history taking is a very important part of treatment planning, every problem either present or past should be revealed along with any medications which you are currently taking. Any history of allergies to any medication should also be mentioned, information regarding pregnancy should be revealed as GA agents can lead to spontaneous abortion in early pregnancy and complications in late pregnancy.

So it is very important for the patient to furnish any past medical history without hiding anything to avoid any complications during General Anesthesia.

Medications which interact with General Anesthesia:

ACE Inhibitors or Angiotensin-converting enzymes: Captopril and Enalapril

Being Vasodilators, these are used in high blood pressure (hypertension), congestive heart failure, kidney problems caused by diabetes, and given after an episode of a heart attack. They interact with General anesthetic agents by having a similar function thus leading to hypotension and rapid fall in Blood pressure.

Antibiotics: Aminoglycosides (Gentamycin, Neomycin, Amikacin) and polymixins (Polymixin B)

These interact with neuromuscular blocking drugs which prolong the length of blocks, Renal toxicity with long term therapy or in combination with other diuretics

Anticoagulants: Oral – warfarin, nicoumalone. Intravenous – heparin

Patients on anticoagulants have increased risk of hemorrhage during intubation, insertion of central lines, local or regional anesthesia, surgery, insertion of a nasogastric tube.

Anticonvulsants: barbiturates, phenytoin, carbamazepine

These induce hepatic enzymes which increase the requirement of doses of induction agents and opioids.

• Benzodiazepines: It leads to addictive effects with other CNS depressants, a withdrawal syndrome may be precipitated in the case of flumazenil.

Beta-Blockers: Atenolol, metoprolol, oxyprenolol, propranolol, sotalol, etc.

Beta-blockers cause negative ionotropic effects which along with the vasodilation caused by GA agents lead to hypotension.  With the use of Beta-blockers, the pulse rate becomes a poor guide to blood loss on the operating table.

Diuretics: Thiazides and loop diuretics

• Low Potassium or Hypokalemia lead to dysrhythmias and also lead to prolonged neuromuscular blockade can be caused due to use of Thiazides.
• In the case of loop diuretics, it leads to Hyponatraemia (low Sodium content in the blood)
• Use of Lithium along with General Anesthesia prolongs the effect of non-depolarizing neuromuscular-blocking drugs.

Calcium Antagonists: diltiazem, nefedipine, isoflurane, enflurane and halothane are non-specific calcium antagonists that may lead to hypotension. Verapamil leads to bradycardia along with decreased antrioventricular conduction. Digoxin leads to toxicity, predisposing to arrhythmias, potentiated by suxamethonium.

Tricyclic antidepressants: potentiated the effects of exogenous catecholamines causing arrhythmias, for example, adrenaline, when it is used as a vasoconstrictor in local anesthetics or to reduce bleeding.

Monoamine oxidase inhibitors (MAO): Isocarboxazid, phenelzine, tranylcypromine

Interactions are very uncommon but can lead to fatal interactions in combination with opioids such as pethidine and sympathomimetics. MAO’s should be stopped two weeks before surgery.

Steroids: Hypotension is seen during the induction of general anesthesia. For patients with long term treatment, supplementary doses are required. Adrenocorticol supression is seen in patients who have taken the medicine in the past 3 months.

These are some of the most commonly used medications on a daily basis for any underlying medical condition by patients which can have interactions with General Anesthesia agents.