Pharmacology Flashcards
What is carbimazole used for?
Hyperthyroidism
What is carbimazole’s MOA?
inhibit thyroid peroxidase resulting in less T3/T4 precursors –> decreased thyroid hormones output
What is carbimazole dosing frequency and ROA?
PO once daily
What happens to carbimazole after absorption?
Converted into active methimazole in the serum
What is carbimazole’s (or its metabolites’) half life?
Methimazole’s half-life 4-6 hour
Does carbimazole (or its metabolites) bind to plasma proteins?
No
How long does it take for carbimazole to exert its effect?
> 90% inhibition achieved within 12 hours, however clinical response may take 3-6 weeks after initiation due to thyroid stores in the body and T4’s long half life.
How is carbimazole metabolized?
CYP450 and FMO enzymes
How is carbimazole excreted?
> 90% excreted in urine as methimazole or its metabolites
What are adverse effects of carbimazole?
Rashes
Joint pains
Nausea
Jaundice
Agranulocytosis (rare)
What is levothyroxine used for?
Hypothyroidism
What is levothyroxine’s MOA?
Synthetic thyroid hormone
What can affect levothyroxine’s absorption?
Increased absorption with fasting
Erratic absorption with dietary fiber
Affected by gastric pH
What is levothyroxine’s bioavailability?
70-80%
How long does it take for levothyroxine to exert its effect?
PO: 3-5 days
IV: 6-8H
What is levothyroxine’s half-life?
7 days
Does levothyroxine bind to plasma proteins?
Yes, >99%
How is levothyroxine being metabolized?
Liver - glucuronidation, sulphation
Kidney - deiodination
How is levothyroxine being excreted?
Primarily by kidneys
What are adverse effects of levothyroxine?
Reduced appetite
Anxiety, insomnia
Hair loss
Diarrhea
Rare and serious:
Heart issues
Seizures
When is IV form of levothyroxine used?
Myxoedema coma (severe form of hypothyroidism)
Cannot use PO levothyroxine as there is reduced blood flow to GI
Can also use IV Liothyronine (synthetic T3)
What should you monitor after initiation of levothyroxine therapy?
Serum TSH every 6-8 weeks after initiation or dose titration
What does persistently elevated TSH levels indicate after levothyroxine therapy has been started?
Inadequate dosing, poor compliance, malabsorption, DDI or food-drug interaction
What is tamoxifen used for?
Breast cancer in both pre- and post- menopausal women
What is tamoxifen’s MOA?
selective estrogen receptor modulator (SERM)
competitively blocks endogenous estrogen binding to the estrogen receptor in the target tissue
Does tamoxifen have stereoisomers?
Yes
Tamoxifen exists in cis- (estrogenic) and trans- (anti-estrogenic) stereoisomers
How is tamoxifen’s absorption profile like?
Rapidly and extensively absorbed in intestine
F ~100%
Css typically reached after 3-4 weeks (max 16 weeks)
Tmax is 3-7 hours
Does tamoxifen bind to plasma protein?
> 98%
What is tamoxifen’s Vd?
50-60 L/kg
high concentrations found in tissues especially uterus (2-3 fold higher than serum) and breast (10 fold higher than serum)
How is tamoxifen metabolized?
Phase 1: hydroxylation, N-oxidation, dealkylation
Phase 2: glucuronidation, sulphation
Major pathway: N-demethylation
What is tamoxifen’s major metabolite and its half-life?
N-desmethyltamoxifen (t1/2 ~14 days)
How is N-demethylation of tamoxifen catalyzed? And what’s the consequences?
By CYP3A4
Should not take with grape gruit or CYP3A4 inhibitors
What are tamoxifen’s minor metabolites?
4-hydroxytamoxifen
4-hydroxy-N-desmethyltamoxifen (endoxifen)
Which of the tamoxifen’s metabolites has greater affinity for the estrogen receptor?
Minor metabolites
What catalyzes metabolism of tamoxifen into its minor metabolites? And what are its consequences?
CYP2D6
Do not take with diphenhydramine or inhibitors of CYP2D6
How is tamoxifen excreted?
Mainly through feces
What are side-effects of tamoxifen therapy?
Anti-estrogenic
- Hot flushes
- Menstrual irregularities
Estrogenic
- Risk of endometrial cancer
- DVT
- Vaginal bleed and discharge
- Nausea/vomiting
Overdose of tamoxifen can lead to?
Acute neurotoxicity eg. tremor, hyperreflexia, unsteady gait, dizziness
How do you treat tamoxifen overdose?
Supportive treatment
What is pembrolizumab used for?
Breast cancer
What is pembrolizumab’s MOA?
PD-1 inhibitor
Binds to PD-1 and prevents PD-L1 on tumor cells binding to it, thus allowing activation of immune response to fight the tumor cells
What type of antibody is pembrolizumab?
Humanized antibody (-zumab)
How is pembrolizumab administered?
IV infusion over 30 mins
What is pembrolizumab’s dose?
IV 200mg every 3 weeks
What is pembrolizumab’s Vd?
~7L
How is pembrolizumab metabolized?
non-specific catabolism (general protein degradation routes) into small peptides and single amino acids
How is pembrolizumab excreted?
No studies done
What is pembrolizumab’s half-life?
~27 days
When will pembrolizumab reach Css?
after ~19 weeks
What can cause slower clearance of pembrolizumab?
Cervical cancer in women
What are S/E of pembrolizumab?
Infusion-related S/Es, immune-related inflammation, joint pain, fatigue, diarrhea, nausea
What are C/I of pembrolizumab?
- On immunosuppressants or corticosteroids
- Pregnancy
- Hypersensitivity
List 4 ways to achieve androgen deprivation
- Inhibition of pituitary gonadotropin release (by using GnRH analogs)
- Inhibition of androgen synthesis
- Inhibition of androgen binding (by using androgen receptor blockers)
- Surgical extirpation of the glands (by castration and adrenalectomy)
What is leuprorelin used for?
Prostate cancer
What is leuprorelin’s MOA?
GLP-1 agonist
It is a synthetic GnRH which activates the pituitary GnRH receptors
Continuous GnRH causes negative feedback on the pituitary leading to reduced FSH and LH levels
Reduced FSH and LH levels suppresses testosterone production in the testes and causes prostate cancer cells (androgen-sensitive cells) to undergo apoptosis
What should you monitor after starting leuprorelin?
Measure PSA in first few weeks of therapy
Measure LH, FSH, and serum testosterone after 4 weeks of therapy
Reduction in levels of these substances indicates that the treatment works
How is leuprorelin administered?
SC or IM, given as single-dose long acting depot (1, 3, or 4 months interval)
What is leuprorelin’s time to Cmax and Css?
Cmax: 1-3 hours post injection
Css typically after 4 weeks
What is leuprorelin’s Vd?
~27L after IV
No data after SC or IM
Does leuprorelin binds to plasma protein?
~45% plasma protein binding (in vitro)
How is leuprorelin metabolized?
degraded proteolytically (peptidases) into inactive peptides
not metabolized in liver CYP450
What is leuprorelin’s half-life?
~ 3 hours
How is leuprorelin excreted?
<5% via urine
What are side effects of leuprorelin?
- Hot flushes (first few weeks)
- Injection site reaction
- Headache/dizziness
- Altered mood
- Hyperglycemia
- Decreased libido
What are C/I to leuprorelin?
Hypersensitivity
Pre-existing heart disease
Pts with risks for osteoporosis
What is bicalutamide used for?
Prostate cancer
What is bicalumatide’s MOA?
Androgen receptor antagonist
Steps:
- Competitive antagonist of androgen receptor
- Inhibits nuclear translocation of the androgen receptors
- Inhibits transcription processes
- Impairing cell proliferation
- Triggers apoptosis of the cancer cells.
Can bicalumatide be used as a monotherapy? Why or why not?
No
Can cause initial surge of testosterone levels, which can lead to the prostate tumor flare
To be used in conjunction with GnRH analogue to alleviate those effects
Does food interferes with bicalutamide’s absorption?
No
Does bicalumatide bind to plasma protein?
> 99%
How is bicalumatide metabolized?
By liver
Active metabolite - slow hydroxylation (CYP3A4) followed by glucuronidation
Which isomer of bicalutamide is active? And its half-life?
R-isomer ~6 days
How is bicalumatide excreted?
Via bile and urine
What is bicalumatide’s S/E?
Constipation/diarrhea
Decreased libido
Fatigue
Hot flushes
Mild swelling of ankles/legs/feet
Nausea/vomiting
What are C/I to bicalutamide?
Hypersensitivity
Women and children
What are oral pharmacotherapy options for managing BPH?
- Alpha adrenergic antagonists (alpha blockers)
- 5-alpha-reductase inhibitors (5ARIs)
- Muscarinic receptor antagonists (MRAs)
- Phosphodiesterase 5 inhibitors (PDE5i)
What is tamsulosin’s MOA?
reversible alpha-1A adrenoreceptor blocker
blocks the contraction of internal sphincter resulting in relaxation of bladder & urethra’s smooth muscle and allowing urine to flow
Can tamsulosin be used on patients with enlarged prostate size?
Tamsulosin can be used for symptomatic BPH regardless of prostate size
What is tamsulosin’s Vd?
0.2L/kg
Does tamsulosin bind to plasma proteins?
> 90%
How is tamsulosin metabolized?
CYP3A4 and CYP2D6
What is tamsulosin’s half-life?
10-15 hours (OD dosing)
How is tamsulosin excreted?
~10% excreted unchanged in urine
What are adverse effects of tamsulosin?
Abnormal ejaculation
Back pain
What are C/I to tamsulosin?
Concurrent use of another alpha-1-receptor antagonist
What is finasteride’s MOA?
5-alpha reductase inhibitor (competitive and specific)
Inhibits the conversion of testosterone to DHT, hence decreasing prostate size
What is finasteride’s bioavailability?
F ~0.65
Is there any dose adjustment of finasteride required for renal/liver failure or elderly patients?
No dose adjustment required
Is finasteride bound to plasma protein?
~90%
How is finasteride metabolized?
CYP3A4
What is finasteride’s half-life?
~6 hours
How is finasteride excreted?
50% unchanged in feces
Metabolites in urine and feces
What are S/E of finasteride?
Decreased libido and sexual potency
Gynecomastia (rare)
What are C/I to finasteride?
Women and children
Pregnancy
What is sildenafil used for?
Erectile dysfunction
What is the MOA of sildenafil?
PDE5 inhibitor (specific to PDE5 in penis)
Inhibits PDE5 to decrease degradation of cGMP
Increased cGMP levels results in smooth muscle relaxation and increased blood flow to the corpora cavernosa
What is the onset of sildenafil?
30-60 mins
What is the bioavailability of sildenafil?
F ~0.4
Is there any dose adjustment of sildenafil required for renal/liver failure or elderly patients?
No
What is the maximum duration of action of sildenafil?
~12 hours
How is sildenafil metabolized?
Major - CYP3A4
Minor - CYP2C9
What is sildenafil’s half-life?
~4 hours
How is sildenafil excreted?
Metabolites: 80% in feces, 13% in urine
Unchanged: in urine
What are S/E of sildenafil?
- Headache
- Flushing
- Dizziness
- Blurred vision
- Blue-green tinting of vision (retinal PDE6 inhibition)
- Priapism
- Back pain
- Dyspepsia
What are C/I to sildenafil?
Cardiac patients on GTN or nitrates
What is ethinyl estradiol’s MOA?
Synthetic estrogen (estrogen receptor agonist)
Causes decreased FSH release from anterior pituitary and hence suppresses the development of ovarian follicle
Make endometrium unsuitable for implantation of ovum
What is ethinyl estradiol used for?
- Menopausal symptoms
- Gynecological disorders
- Certain hormone sensitive cancers
What is the onset and bioavailability of ethinyl estradiol?
30-60 min
F ~0.45
Is ethinyl estradiol protein bound?
~98%
How is ethinyl estradiol metabolized?
Phase I - hydroxylation by CYP3A4
Phase II - glucuronidation (ethinyl estradiol glucuronide) and sulfation (ethinyl estradiol sulfate)
Ethinyl estradiol sulfate undergoes enterohepatic recirculation
What is the half-life of ethinyl estradiol?
13-27 hours
How is ethinyl estradiol excreted?
Feces and urine
What are the adverse effects of ethinyl estradiol?
- Breast tenderness
- Headache
- Dizziness
- Nausea
- Fluid retention
- Weight gain
- Risk of VTE
- Risk of MI/stroke
- Liver damage
What are C/I to ethinyl estradiol?
- Breastfeeding and <21 days postpartum
- Breast cancer
- Hx of DVT
- Advanced diabetes with vascular disease
- HTN ≥ 160/100
What is norethindrone’s MOA?
Synthetic progestin (progesterone receptor agonist)
Reduces LH release which prevents ovulation + make endometrium unsuitable for implantation of ovum
What is norethindrone used for?
- Endometriosis
- Abnormal periods or bleeding
What is norethindrone’s bioavailability?
F ~64%
Does norethindrone bind to plasma protein?
Yes, highly bound
How is norethindrone metabolized?
Phase I - reduction
Phase II - glucuronidation and sulfation
What is norethindrone’s half-life?
~8 hours
How is norethindrone excreted?
Metabolites excreted 50% in urine and 40% in feces
What are S/E of norethindrone?
- Headache
- Dizziness
- Bloating
- Weight gain
- Amenorrhea
- Initial spotting and bleeding
Why is norethindrone to be used with caution in ppl with cardiovascular risk?
Partial conversion of norethindrone to ethinyl estradiol
What is the MOA of metformin?
Biguanides
Decreases gluconeogenesis in the liver
Enhance tissue sensitivity to insulin
What is the bioavailability of metformin?
40-60%
What is the duration of action of metformin?
8-12 hours
Does metformin bind to plasma protein?
Minimal
What is the half-life of metformin?
3 hours
How is metformin excreted?
Unchanged in the urine
What are the S/E of metformin?
Anorexia
GI disturbances
Increased risk of vit B12 malabsorption
Does metformin cause weight loss or gain?
Weight loss
In which patients should metformin be used cautiously?
Patients who experienced lactic acidosis
Patients with renal problems
What is glipizide’s MOA?
Sulfonylureas
Binds to SU receptor protein (found at the K(ATP) channels, inhibiting K+ efflux and hence triggering a calcium-dependent exocytosis of insulin granules from the pancreatic beta cells
What is glipizide’s oral bioavailability?
> 95% (delayed with food intake)
What is glipizide’s onset of action?
0.5 hours
What is glipizide’s duration of action?
12-24 hours
Does glipizide bind to plasma proteins?
Yes, 99%
What is glipizide’s half-life?
4 hours
How is glipizide metabolized?
Hydroxylation in the liver
How is glipizide excreted?
<10% excreted unchanged in urine and feces
Metabolites are excreted in urine and feces
What is the S/E of glipizide?
Weight gain
Hypoglycemia (less than 1st gen, more likely in elderly)
What is the MOA of sitagliptin?
DPP-4 inhibitor
Inhibit DPP-4 to prevent enzymatic degradation of GLP-1 and prolong the action of endogenous incretins
Incretins stimulate insulin secretion at the beta pancreatic cells WHEN there is presence of hyperglycemia, suppresses alpha pancreatic cells mediated glucagon release and hepatic glucose production
Incretins also delay gastric emptying at the gut and induce satiety
What is the oral bioavailability of sitagliptin?
F = 87%
What is sitagliptin’s half-life?
10-12 hours
How is sitagliptin metabolized?
low liver metabolism
How is sitagliptin excreted?
80% excreted unchanged in urine, rest in feces
What are S/E of sitagliptin?
GI disturbances
Flu-like symptoms
Skin reactions
In which patients should sitagliptin be used cautiously?
In patients with history of pancreatitis
What is liraglutide’s MOA?
GLP-1 agonist
Activates GLP-1 receptor on pancreatic beta cells to increase insulin secretion, and on alpha cells to decrease glucagon release (GLUCOSE DEPENDENT)
Delays gastric emptying and induces satiety (reduce appetite)
It is a long acting peptide (C16 fatty acid) and hence is resistant to degradation by DPP-4 enzymes in the body.
What is liraglutide’s bioavailability after SC injection?
F = 55%
How is liraglutide dosed?
Week 1 - 0.6 mg SC daily
Week 2 - 1.2 mg SC daily
Week 3 - 1.8 mg SC daily
Week 4 - 2.4 mg SC daily
Week 5 onwards - 3 mg SC daily
Does liraglutide bind to plasma protein?
Yes (C16 fatty acid binds to plasma protein)
What is the half-life of liraglutide?
13 hours (due to plasma protein binding)
How is liraglutide metabolized?
Non-specific, similar to endogenous polypeptides
How is liraglutide excreted?
Little or none excreted unchanged
What are S/E of liraglutide?
Nausea, vomiting
Diarrhea, constipation
Headache, tiredness
Who should liraglutide not be used on?
Pregnant women
What are other benefits of liraglutide?
- Weight loss
- Reduces risk of CV death, non-fatal MI, and HF (IN DM2 LECTURE SAY NEUTRAL EFFECT) among T2DM patients
What is the MOA of empagliflozin?
SGLT2i
Binds to SGLT2 at the proximal tubule of the nephron and decrease reabsorption of filtered glucose, increasing urinary glucose excretion
What is the oral bioavailability of empagliflozin?
60-80%
When is the Cmax achieved for empagliflozin?
1-2 hours
What is the half-life of empagliflozin?
12 hours
Does empagliflozin bind to plasma protein?
~90%
How is empagliflozin metabolized?
Minimal metabolism
Glucuronidation in the liver
How is empagliflozin excreted?
40% unchanged in feces
27% unchanged in urine
What are the S/E of empagliflozin?
- UTI
- increased urination
- female vaginal thrush
- diabetic ketoacidosis
What are additional benefits of empagliflozin?
- Reduced risk of major cardiac event (ASCVD and HF)
- Reduced risk for composite endpoint of worsening renal function (CKD)