Pharmacology Flashcards
Gut absorption is most affected by which property of a drug?
Absorption is proportional to lipid solubility of the drug
Other factors that influence absorption:
Gastric pH
GI transit time
Mucosal permeability
List 3 ways drugs are eliminated from the body
- Elimination in urine**most drugs
- Metabolism (usually by liver)
- Uptake by liver and elimination in bile
What type of elimination kinetics do most drugs exhibit?
First order
Zero order if enzymes are fully saturated (rate of elimination does not change with concentration of drug)
How do you calculate clearance of a drug?
Clearance refers to the ability of the kidney and liver to remove a drug
Clearance=Volume of distrubtion x (0.69/half life)
What is bioavailability?
Proportion of administered drug reaching the systemic circulation
e.g. IV drugs=1000% bioavailiabiity
Affected by first pass metabolism and gut absorption
List 3 reasons for drug metabolism
- To make the drug more hydrophilic to help with excretion in kidney (lipophollic drugs are reabsorbed in renal tubules and would have VERY prolonged action without metabolism)
- Render drug less active
- To render drug active (prodrug)
Explain why cytochrome P450 dependent oxidation results in drug interactions
Liver is the main organ of drug metabolism
Cytochrome P450 oxidizes a bunch of lipophilic drugs (helping to render them more hydrophilic and easily excreted by kidney)
Some drugs INDUCE cytochrome P450:
Increases metabolism of cytochrome P450 dependent drugs
Some drugs INHIBIT cytochrome P450:
Reduces metabolism of cytochrome P450 dependent drugs
List 5 drugs that are substrates for cytochrome P450
Phenobarbital Cisapride Cyclosporine Tacrolimus Macrolides (except azithromycin) Benzodiazepines (diazepam, midazolam) Protease inhibitors Calcium channel blockers (eg, amlodipine) Atorvastatin, simvastatin, lovastatin
What are phase I and phase II reactions?
Describe the steps in drug metabolism in the liver
Phase I
-Most common is oxidation, others are reduction or hydrolysis
Phase II
- Conjugation of drug or Phase I metabolite
- Usually results in less active metabolite that is polar and readily excreted in kidneys
Which drugs induce cytochrome P450?
- Rifampin
- Phenytoin
- Phenobarbital
- Carbamazepine
- Nevirapine, efavirenz
- St. John’s Wort
Which drugs inhibit cytochrome P450?
- Erythromycin, clarithromycin (3A4)
- Ketoconazole, itraconazole (3A4)
- Valproic acid
- HIV protease inhibitors (eg, ritonavir)
- Fluoxetine, paroxetine, codeine (2D6)
- Nefazodone (3A4)
- Grapefruit juice (intestinal CYP 3A4 only)
What is the difference in volume of distribution between infants <6 months and older kids?
Infants <6 months have greater volume of distribution (because 75% total body water!)
How is the activity of many cytochrome P450 enzymes and glucuronsyltransferases different in the first 2 months of life?
Activity of many cytochrome P450 enzymes and glucuronsyltransferase is significantly decreased in the first 2 months of life
List 5 differences between neonates and older kids in pharmacokinetics
- Decreased activity of cytochrome p450
- Greater volume of distribution (more water!)
- Gastric emptying time longer
- Greater mucosal permeability
- Decreased renal clearance function
- Lower protein-binding of drugs
As a result, neonates have LOWER BLOOD CONCENTRATIONS of drugs
List 3 adverse effects of carbamezipine
SJS Agranulocytosis Liver toxicity Tics Hyponatremia Weight gain Dizziness Nausea
List 2 adverse effects of gabapentin
Acute onset of aggression
Hyperactivity
List 3 adverse effects of lamotrigine
SJS
Liver toxicity
CNS effects-headache, ataxia, dizziness, tremor
List 3 adverse effects of levetricetam
Behavioural symptoms Less CNS effects than other AEDs: Somnolence Dizziness Asthenia
List 3 adverse effects of phenobarbitol
SJS Liver toxicity Insomnia Neurotoxicity Hyperactivity Fluctuation in mood
List 3 adverse effects of phenytoin
Concentration dependent: ataxia, nystagmus, dizziness, headache, sedation, visual blurring, diplopia, cognitive impairment
Idiosyncratic:blood dyscrasias, rash(SJS and TEN rare)
Chronic: gingival hyperplasia, folate deficiency, osteomalacia, skin thickening, hirsutism, coarsening of facial features
Rare: DRESS, SLE-like syndrome
List 3 adverse effects of valproic acid in the following categories:
Dose dependent
Idiosyncratic
Chronic
Dose dependent: GI upset Sedation Unsteadiness Tremor Thrombocytopenia
Idiosyncratic:
Acute hepatic failure
Acute pancreatitis
Alopecia
Chronic: Weight gain Hyperammonemia Menstrual irregularities Polycystic-ovary-like syndrome Decreased serum levocarnitine
List 3 adverse effects of topiramate
Precipitation of glaucoma Renal stones Weight loss Cognitive dysfunction Hypohydrosis
Most important adverse effect of vigabatrin
Retinopathy***
Irrerversible visual filed deficits
Hyperactivity
What medications cause acute dystonic reactions?
Antipsychotics, anti-emetics, and antidepressants
What medications cause acute dystonic reactions?
Anti-dopaminergics:
Antipsychotics, anti-emetics, and antidepressants
List 3 clinical features of acute dystonic reaction
- Oculogyric crisis
- Torticollis
- Widely open mouth, tongue protrusion, trismus
- Laryngospasm!!
Treatment of acute dystonic reaction
IV diphenhydramine or benztropine
List 3 adverse effects of inhaled corticosteroids
- Growth deceleration, resulting in 1.2 cm reduction in adult height
- Oral thrush
- Dysphonia
- Rare-adrenal insufficiency, increased IOP
List 10 side effects of systemic steroids
- Striae
- Acne
- Alopecia
- Hirsutism
- Cushingoid appearance
- Elevated IOP
- Increased risk of cataracts
- HTN
- Increased risk of atherosclerosis
- PUD
- Gastritis
- Steatohepatitis
- Osteoporosis
- AVN
- Insomnia
- Behavioural change (euphoria, depression, mania)
- Increased risk of DM2
- Adrenal suppression
- Increased risk of infections
List 5 adverse affects of anabolic steroids
-Suppression of endogenous testicular function ➢ Decreased spermatogenesis and fertility – returns to normal 4mo after stopping ➢ Testicular size may decrease if using for many years -Gynecomastia -Erythrocytosis -Hepatotoxicity -Psychological disorders -Decrease in HDL -Coagulation activation -Premature epiphyseal fusion -Infections -Virilization in women -Risky and violent behavior -?Liver cancer
What is redman syndrome and what drug causes it?
RMS is an idiopathic rate-dependent infusion reaction, not a true allergic reaction
Typically caused by IV vancomycin
Characteristics:
o Flushing/erythema
o Pruritus
o Upper body, neck, and face more than the lower body
o Pains and muscle spasms in the back and chest
o +/- Dyspnea, hypotension
Treatment of redman syndrome
- For mild to moderate reactions (HD stable) → stop infusion → treat with diphenhydramine and ranitidine →restart at ½ original rate
- For severe reactions (e.g. muscle spasm, chest pain, hypotension) → same as previous but may need IV fluids, and run vanco even slower over 4 hours