Drug interactions Flashcards
Name the 3 categories of drug interactions
- pharmacokinetic
- pharmacodynamic
- pharmaceutical interactions
What is a pharmacokinetic interaction
When the presence of one drug affects the concentration of another drug at its site of action
What aspect can be affected by pharmacokinetic interactions
- absorption
- Distribution
- Metabolism
- Excretion
Give an example of a pharmacokinetic interaction that affects drug absorption
local anaesthetics and adrenaline
Give an example of a pharmacokinetic interaction that affects drug distribution
Warfarin and aspirin where aspirin displaces warfarin from protein binding sites there for increasing the effective warfarin concentration
Give an example of a pharmacokinetic interaction that affects drug metabolism
Beta adrenergic blocking drugs and local anaesthetics
Where the reduction in hepatic blood flow produced by the Beta adrenergic blocking drugs may increase the toxicity of LA
Give an example of a pharmacokinetic interaction that affects drug absorption
probenecid inhibits the excretion of penicillin
What is a pharmacodynamic interaction
Where the drug effect is modified without its concentration at the site of action being affected
Drugs may act as agonist or antagonist
Give an example of beneficial agonist pharmacodynamic interaction
antibacterial drug cotrimoxa-zole relies on the combined action of two drugs: sulfamethoxazole and trimethoprim
these interfere at two different stages in bacterial folic acid production
Give an example of an adverse agonist pharmacodynamic interaction
Sedative agents used in dental practice combined with other CNS depressants such as alcohol can lead to respirate distress
Give an example of beneficial antagonist pharmacodynamic interaction
flumazenil antagonises the effects of midazolam and can be used to reverse sedation
Give an example of an adverse antagonist pharmacodynamic interaction
the action of salbutamol, a β2-adrenergic agonist used in the routine and emergency management of asthma is antagonised by β-adrenergic blocking drugs.
How do we classify drug interactions in dentistry
ACT system:
Avoid
Caution
Theoretical
List the common drugs used in dentistry
- LA
- Vasoconstrictors
- Benzodiazepines
- Aspirin
- Ibuprofen
- Paracetamol
- Penicillins
- Erythromycin
- Metronidazole
- Tetracyclines
- Clindamycin
- Antifungals
What does theoretical mean in terms of the ACT classification for interactions
denotes that an interaction is theoretically possible but unlikely to occur at the doses used in clinical dentistry.
What groups of drugs can LA interact with and give the ACT classification for the interaction
- OTHER LA: T
- Antimicrobials: C
- Benzodiazepines: C
- Cardiovascular drugs: C
- Other local anaesthetics drugs: C
- Muscle relaxants: T
What groups of drugs can vasoconstrictors interact with and give the ACT classification for the interaction
- Analgesics: C
2, Social drugs: C - Cardiovascular drugs: C
- CNS drugs: C
What groups of drugs can ibuporfen interact with and give the ACT classification for the interaction
- Analgesics: C
- Anticoagulants: C
- Antidiabetics: C
- Antimetabolites: A
- Cardiovasulcar drugs: A
- CNS drugs: A
- Corticosteroids: A
- Muscle relaxants: C
What groups of drugs can benzodiazepines interact with and give the ACT classification for the interaction
- Analgesics: A
2, Social drugs: A - Antiasthma drugs: C
- Antimicrobials: A
- Other benzodiazepines: C
- Cardiovascular drugs: C
- CNS: drugs A
- LA: C
- Muscle relaxants: T
- Oral contraceptives: T
- GI tract drugs: C
What groups of drugs can Paracetamol interact with and give the ACT classification for the interaction
- Anticoagulants: C
- GI tract drugs: T
What groups of drugs can Aspirin interact with and give the ACT classification for the interaction
- Analgesics: C
- Anticoagulants: A
- Anticonvulsants: A
- Antidiabetic: A
- Antimetabolites: A
- Cardiovascular drugs: C
- Corticosteroids: A
- GI tract drugs: T
- Drugs used in gout: T
What groups of drugs can penicillin interact with and give the ACT classification for the interaction
- Analgesics: T
- Anticoagulants: C
- Antimetabolites: A
- Antimicrobials: A
- Cardiovascular drugs: T
- Drugs used in GI tract: C
- Oral contraceptive: C
What groups of drugs can erythromycin interact with and give the ACT classification for the interaction
- Social drugs: A
- Anstiasthama: C
- Anticoagulants: C
- Antidiabetics: C
- Antihistamine: A
- Antimetabolites: A
- Cardiovascular drugs: C
- CNS drugs: A
- Corticosteroids: T
- GI tract drugs: A
- Drugs used in gout: C
- Immunosuppressants: A
- Lipid lowering drugs: C
- Oral contraceptive: C
What groups of drugs can metronidazole interact with and give the ACT classification for the interaction
- Social drugs: A
- Anticoagulants: A
- Anticonvulsant: C
- Antimetabolites: c
- Antimicrobials: C
- CNS drugs: A
- Corticosteroids: c
- GI tract: C
- Immunosuppressants: C
- Lipid lowering drugs: C
- Oral contraceptive: C
What groups of drugs can tetracycline interact with and give the ACT classification for the interaction
- Antiasthmastic: C
- Anticoagulants: C
- Antidiabetics: A
- Antimetabolites: C
- Antimicrobials: A
- Cardiovascular drugs: C
- Cations: C
- CNS drugs: C
- GI tract drugs: C
- Oral contraceptive: C
- Retinoids: C
What groups of drugs can Antifungals interact with and give the ACT classification for the interaction
- Anticoagulants: A
- Anticonvulsant: C
- Antidiabetics: C
- Antihistamine: A
- Antimicrobials: C
- Benzodiazepines: C
- Cardiovascular drugs: C
- Corticosteroids: C
- Immunosuppressants: C
What is a side effect of some local anaesthetics
Methaemoglobinaemia
What is Methaemoglobinaemia cause dby
Iron in the haemoglobin being in the ferric rather than ferrous form
This reduces oxygen carrying capacity
How does Methaemoglobinaemia present
As cyanosis
Which drugs combined with LA can increase likelihood of Methaemoglobinaemia
sulfonamide antIbacterials, and combined therapy
What effect can midazolam have on lidocaine
reduces the CNS toxicity of the local anaesthetic (This is beneficial)
What effect can diazepam have on bupivicaine
diazepam can increase the toxicity of bupivacaine by raising the serum levels of the LA
What should we be mindful of when giving LA to a patient on beta blockers
Large doses of LA should be avoided (nb 1-2 cartridges is no problem)
Give an example of a calcium channel blocker that can increase the toxicity of lidocaine
Verapamil (not a concern with 1-2 cartridges)
What effect can calcium Channel blockers have on bupivicaine
increase the cardiotoxicity of the long-acting local anaesthetic bupivacaine
How do Antihypertensive drugs interact with adrenaline
Can increase systolic blood pressure which coudl cause a cerebrovasicualr attack
1-2 cartridges s fine but if you need to give more consider an adrenaline free option
How does adrenaline affect plasma concentration
Decreases plasma potassium levels
When is the decreasing potassium levels effect heightened in patients following adrenaline
In patients taking non potassium sparring diuretics or calcium channel blocker (nb 1-2 cartridges is safe)
What effect do tricyclic antidepressents have on adrenaline
They can decrease the re uptake of adrenaline into nerve cells resulting in the pressor effects of adrenaline being increased (nb 1-2 cartridges is safe)
Give examples of recreational drugs that can increase adrenaline toxicity
Amphetamines, cannabis and cocaine
If we suspect a pt has taken amphetamine cannabis or cocaine what shoudl we do
Avoid or limit the amount of adrenaline containing LA for at least 24 hours following drug use
Which drugs should be avoided if offering a patient sedation
Drugs affecting the CNS as over sedation can lead to respirate depression
Which drugs should be avoided if offering a patient sedation
Drugs affecting the CNS as over sedation can lead to respirate depression
