Case Study Pharmacology on Ms Johnson
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Case Study Pharmacology on Ms Johnson
Ms. Johnson, a 29-year-old female presents to your clinic today with complaints of left hip and left shoulder pain. She reports not feeling too well today. She reports that she has been in pain for the last 6 years. She denies trauma. There is no neurological involvement including bowel or bladder changes or dysfunction, radiation of pain to the lower extremities, numbness or tingling. The pain is constant, dull and boring.
Recently, she started an exercise program to build her muscles. She reports her personal trainer is a body builder and suggested that she starts taking Creatinine to help build her muscles, and Coenzyme Q10, an antioxidant. The trainer suggested to start these 2 supplements at the same time when she begins working out. She also takes Kava Kava for anxiety and garlic to help lower her blood pressure.
Past medication history includes: Type II diabetes since age 19, High blood pressure, Recurrent deep vein thrombosis.
Current medications: Glyburide 3 mg daily with breakfast, Lisinopril 20 mg daily, Ibuprofen 400mg BID, and Warfarin 7mg daily.
1. After reviewing the patient’s medication list, state your findings and explain your concerns in detail.
2. What additional information would you obtain? Please discuss rationale.
3. Give your recommendations to manage this patient’s medications?
4. Provide patient education.
5. If your plan is to prescribe a medication/s, create a prescription and discuss, what are the important components necessary on the packaging or on the label?
A) Introduction, Drug Administration Routes
1. A four-year-old child is admitted to the hospital with a fever, cough, breathing trouble, and chest pain.
On examination, he is found to have a high pulse (118/min), rapid breathing (RR 55/min), indrawing of the lower chest on inspiration, wheezing, crepitations, and slight dehydration.
The temperature in my body is 40 degrees Celsius (1040F).
A tentative diagnosis of acute pneumonia is made by the doctor, who then orders pertinent haematological and bacteriological tests.
He makes the decision to start antibiotic medication.
a) Which mode of administration will be most appropriate in this scenario if he chooses an antibiotic that may be administered orally as well as by i.m. or i.v injection?
b) Should the paediatrician start treating the child with antibiotics right immediately or wait for the laboratory results?
Answers
1.
a) Because the youngster is critically unwell, the antibiotic must operate quickly and predictably; a parenteral method of administration is appropriate.
Furthermore, because the youngster is dull and fussy, oral dosing may be problematic in this scenario.
In youngsters, getting a vein for an i.v. injection might be challenging, especially if they are dehydrated.
As a result, the antibiotic can be injected intramuscularly; however, if an intravenous line is set up for rehydration, the antibiotic can be given through the intravenous line.
b) Because the child is critically unwell, the provisionally selected antibiotic may be amoxicillin, which should be begun as soon as feasible.
The prognosis may be jeopardized while waiting for lab results to confirm the diagnosis/select the appropriate antibiotic.
B) Calculations of dose
2. A 49-year-old male patient weighing 83.3 kilograms will be given an immediate-release carbamazepine regimen.
a) Assuming monotherapy, calculate the daily dose required to achieve a steady-state plasma concentration of 7.5 mg/L.
b) If the patient has been taking phenobarbital at a dose of 2.0 mg/kg Q12h for the past three months and the doctor decides to add carbamazepine as a concomitant therapy to improve seizure control, compute the daily maintenance dose required to achieve a target steady state concentration of 7 mg/L carbamazepine using an immediate release formulation.
Blood samples were then tested for carbamazepine throughout therapy and were found to contain 12.5 mg/L.
To get the appropriate concentration, how should his daily dose be adjusted?
3. Mala, a 49-year-old female weighing 55 kilograms, had been taking 250 milligrams of sodium phenytoin per day; however, her dose had been increased to 300 milligrams per day because her seizures were uncontrollable and her phenytoin plasma concentration was only 3 milligrams per liter.
Her measured plasma phenytoin content is 26mg/L, and she now complains of modest CNS adverse effects.
The maintenance dose was stopped since this level was determined to be too high for this patient.
How long would it take for the phenytoin level to drop to 15 mg/L once the medication was stopped?
The equation below may be useful in resolving this issue:
4. Aszad, a 75-year-old non-obese man weighing 65 kg, was admitted with complains of shortness of breath and yellow sputum.
He’s had congestive heart failure in the past.
He developed atrial fibrillation during his hospital stay and was given digoxin to reduce his ventricular rate.
He was given three 0.25-mg digoxin IV doses every three hours (beginning at 9 p.m. on day 1), as well as a daily maintenance dose of 0.25-mg tablets (starting at 9am on day 2).
His serum creatinine level has remained constant at 1.3 mg/dL.
Calculate his digoxin plasma concentration on day 4 at 9 a.m.
(Hint: To solve this problem, a graph showing the expected concentration time profile would be useful.)
5. Which of the following combinations of pharmacokinetic changes best describes the elderly and neonates?
(The PK features of these groupings are comparable.)
1) Inadequate renal clearance
2) There’s a lot less body water.
3) Insufficient metabolic clearance
4) Protein binding is reduced.
5) Half-lives that are longer
A) 1 and 4 B) 1, 3, and 4 C) 1, 4, and 5 D) 1, 3, 4 and 5 all of the above
6. The effect of carbamazepine on the pharmacokinetics of medication X after a single oral dose was investigated in a clinical trial.
The figure depicts the average drug X concentration-time profile.
CYP3A4 is known to be the primary metabolizer of medication X.
Make a conclusion after describing the graph.
Closed circles: Drug X on its own
Drug X with carbamazepine (open circles).
This Leseprobe does not include an illustration.
Figure 1 shows the average plasma concentration over time in hours.
7. Vertilmicin is an aminoglycoside that is being studied for its antibacterial properties.
This medication is given as an intravenous bolus.
The kidneys are responsible for 99.9% of the drug’s elimination.
Its elimination is unaffected by tubular secretion or reabsorption.
Vertilmicin does not bind to any plasma proteins.
Calculate the following pharmacokinetic parameters based on this individual’s ideal body weight (male, 47 years old, 70 kg, serum creatinine 2.1 mg/dL):
Clearance (a)
(b) Half-life, assuming a 0.35 l/kg relationship between distribution volume and body weight.
8. A 250 mg IV bolus dose of drug X is given.
The plasma concentration was 5 mg/L two hours after injection and 1 mg/L ten hours after administration.
The medication is a lipophilic molecule that the liver clears.
The patient’s liver blood flow is 90 liters per hour.
0.6 percent of the medication is bound to tissue.
a) The time it takes to go to C0.
b) Calculate Vd
b) Indicate whether this medicine has a high or low extraction rate.
Calculate the extraction ratio for this drug assuming hepatic clearance is 80% of total body clearance.
d) Would you expect a change in clearance if Drug Y stimulates the enzymes responsible for Drug X metabolism?
Answers
2.
a) Carbamazepine has a monotherapy clearance of 0.064 L/h/kg.
The oral bioavailability of carbamazepine for immediate release is 0.8.
This Leseprobe does not include an illustration.
b) For polytherapy, carbamazepine has a clearance of 0.1 L/h/kg.
This Leseprobe does not include an illustration.
3.
This Leseprobe does not include an illustration.
4.
This Leseprobe does not include an illustration.
5. The correct answer is D.
It denotes low renal and metabolic clearance, as well as reduced protein binding and longer half-lives.
6.
a) When Drug X is taken alone, the peak plasma concentrations and AUC are higher than when carbamazepine is added.
b)Carbamazepine is a strong inducer of CYP3A4, which has a considerable impact on Drug X concentrations.
7.
This Leseprobe does not include an illustration.
8.
a) Assuming no loading dosage and a constant dosing interval, a medication with a higher degree of accumulation takes less time to achieve steady state.
b) There is only one volume of distribution in a multicompartmental body model.
So it’s only 0.6.
c) The induction of hepatic biotransformation enzymes will affect the clearance of medicines with low extraction.
d) Assuming that the distribution volume remains constant, when clearance falls, it will take longer to reach steady state, resulting in a longer half-life.
The absence of a statistically significant difference in the rate and extent to which the active medicinal ingredient becomes accessible is defined as bioequivalence.
Therapeutically, bioequivalent products are interchangeable.
C) Drug pharmacokinetics
9. A 60-year-old woman complained of fatigue, weakness, and lethargy.
Her iron deficiency anemia (Hb. 8g/dl) was discovered during the investigation.
Ferrous fumarate cap. Ferrous fumarate cap. Ferrous fumarate cap. Ferrous fumarate cap. Ferrous fumarate cap. Ferrous
After a month, she returned with no change in her symptoms.
Her hemoglobin level remained constant.
She stated that she was experiencing epigastric distress after taking the test, but the level remained same.
When questioned, she stated that she had experienced epigastric distress after taking the iron capsules and that she had begun taking antacid tablets in addition to the capsules.
What could be the cause of her inability to respond to the oral iron supplement?
Glibenclamide 5 mg twice daily was prescribed to a 50-year-old man with type 2 diabetes.
He got a toothache and took 650 mg of aspirin six times a day.
He had anxiousness, sweating, palpitation, weakness, ataxia, and was acting strangely after taking aspirin.
When he was given a glass of glucose solution, his symptoms went away.
a) What is the most likely cause of his symptoms?
b) Which other analgesic should have been used instead?
Answers that have been solved
9. Gastric acid is essential for oral iron salt absorption.
Antacid pills used at the same time may have hampered iron absorption.
As a result, the anemia did not improve.
Sulfonylureas are displaced from plasma protein binding sites by aspirin.
As a result, after taking aspirin, the plasma concentration of unbound (and active) glibenclamide would have increased, resulting in hypoglycemia and the symptoms.
As a result, consuming glucose alleviated the symptoms.
b) Paracetamol and ibuprofen are analgesics that are as effective as aspirin in treating toothaches and do not displace or interact with sulfonylureas.
As a result, these analgesics are better suited to the individual patient.
Drug Elimination (D)
11. A 30-year-old mother of two 60-kg children was cyclically taking a combined oral contraceptive pill containing levonorgestrel 0.15 mg and ethinylestradiol 30 g. (3 weeks treatment-1week gap).
After a sputum smear examination, she had a fever and cough, and was diagnosed with pulmonary tuberculosis.
For two months, she was given isoniazid (300 mg)+ rifampin (600 mg)+ pyrazinamide (1.5 g)+ ethambutol (1 g) daily, followed by isoniazid (600 mg)+ rifampin (600 mg)+ pyrazinamide (1.5 g)+ ethambutol (1 g) daily (600mg thrice weekly).
She didn’t have the customary withdrawal bleeding during the contraceptive cycle’s gap period in the third month.
Her urine pregnancy test came back positive after ten days.
a) What could be the cause of the oral contraceptive’s failure?
b) What preventive measures may have been taken to avoid the unplanned pregnancy?
12. For generalized tonic-clonic seizures, a 20-year-old patient weighing 60 kg must be provided an antiepileptic medicine (available in 200 and 400 mg tablets).
The following are the drug’s pharmacokinetic characteristics and therapeutic plasma concentration:
Table:1
This Leseprobe does not include an illustration.
For this patient, what should the loading dose and daily maintenance dose of the medicine be?
Answers
11.
Case Study Pharmacology on Ms Johnson
a) Because rifampin is known to induce the metabolism of contraceptive steroids, the steady state blood levels of levonorgestrel and ethinylestradiol could have fallen below the threshold for inhibiting ovulation/ contraception after regular intake of rifampin for more than 2 weeks (necessary for enzyme induction), the steady state blood levels of levonorgestrel and ethinylestradiol could have fallen below the
As a result, the women’s fertility was restored, and they were able to conceive.
b) Given the importance of rifampin (and other antitubercular medications) in this patient’s treatment and the likelihood of the oral contraceptive failing, the couple should have been encouraged to use an additional/alternative contraception such as a condom or intrauterine device.
12..First, determine the total volume of distribution (Vd).
Case Study Pharmacology on Ms Johnson
This Leseprobe does not include an illustration.
For this patient, start with a loading dose of 720 mg, or around 3 12 tablets of 200 mg each.
984 mg/day as a maintenance dosage
One 400 mg tab could be used as a maintenance dosage.
12 tab. (600 mg) in the morning and 12 tab. (600 mg) at night.
Case Study Pharmacology on Ms Johnson
Pharmacodynamics, Pharmacotherapy, and Drug Development (Chapter 2)
1. An oral ulcer, megaloblastic anemia, and other toxic symptoms emerged in a patient receiving methotrexate treatment.
Given that 1) Mtx inhibits the enzyme dihydrofolate reductase (DHFRase), which produces the essential coenzyme tetrhydrofolic acid (THFA) from dihydrofolic acid (DHFA), ii) Mtx binds to the catalytic site of DHFRase with an affinity 50,000 times greater than the natural substrate DHFA, and iii) two forms of folate, folic
a) What kind of enzyme inhibition will Mtx produce?
b) For Mtx toxicity, which form of folate should be used?
2. A 65-year-old male patient with hepatic cirrhosis was admitted to the hospital with gross ascetic fluid.
He responded quickly, but by the third day, he was found to be talking incoherently, weak, and partially disoriented.
When he got out of bed, he experienced a fainting spell.
His blood pH was 7.8 and his serum K+ was 2.8 mEq/L (low) (raised).
Case Study Pharmacology on Ms Johnson
a) What is the most likely reason of his 3rd da condition?
b) What should be the management guidelines for this complication?
Answers
1.
Case Study Pharmacology on Ms Johnson
a) Mtx. will operate as a competitive inhibitor since it binds to the same location of DHFRse as the endogenous metabolite DHFA.
However, because Mtx has a 50,000-fold higher binding affinity for the enzyme, even excess DHFA will not be able to displace it, resulting in a non-equilibrium kind of inhibition.
b) Because folic acid is not converted to the active coenzyme form THFA, it will not be able to counteract Mtx toxicity when taken as a medication.
Folic acid, on the other hand, will provide prepared active coenzyme THFA and hence be able to combat Mtx poisoning.
Case Study Pharmacology on Ms Johnson
a) The occurrence of hypokalaemic alkalosis, which precipitated hepatic encephalopathy, is the most plausible etiology of the symptoms on the third day of diuretic therapy in the patient.
Ammonia (NH3) produced by gut bacteria is not entirely detoxified via conversion to urea in the liver in cirrhotics with moderate to severe hepatic dysfunction, and blood NH3 levels tend to rise.
This ionizes to NH4+ and is eliminated as NH4Cl in the urine.
The NH4+ molecules do not pass across the BBB.
NH3 ionizes to a reduced extent during alkalosis, elevating blood NH3 levels, which enter the brain and produce encephalopathy.
Other symptoms of hypokalemic alkalosis include weakness and postural hypotension.
b) The diuretic should be discontinued until the fluid electrolyte and acid-base balance have been restored.
Hypokalemia and alkalosis can be sped up with an intravenous infusion of KCl and normal saline.
Oral lactulose (a non-absorbable disaccharide) aids in the conversion of blood NH3 to NH4+, which is poorly absorbed.
Stool pH is lowered by lactulose, which suppresses NH3-producing gut bacteria.
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