Pharmacology

Question 1

Treatment for influenza

Answer 1

Oseltamivir (Tamiflu) 75 mg BID for 5 days *start asap

Question 2

Describe pharmacokinetic changes during pregnancy related to absorption, distribution, metabolism, and excretion.

Answer 2

• Absorption
  
  • Decreased w/ gestational N/V → decreased plasma concentrations
  • Gastric pH increased → changes bioavailability for drugs dependent on low pH for absorption or activation
  • Longer intestinal transport/gastric emptying → increased absorption of hydrophillic drugs.
    
    • No change to lipophilic drugs
• Distribution
  
  • Plasma volume expands
  • Increased volume of distrubution as fetal compartment grows → may ave lower serum levels and may need to increase hydrophillic drug doses
  • Reduced plasma proteins (esp albumin) → higher levels of free drug
  • Plasma levels of estrogen/progesterone compete with protein-bound drugs → higher concentrations of free drug
  • Concentration gradient favorable to transport drug from parent → fetus as fetal albumin production increase (ie higher concentrations of valium in fetus than parent)
• Metabolism
  
  • Blood flow through liver not changed → no significant change to first pass effects
  • CYP450 affected by progesterone/estrogen → slower metabolism of some drugs and faster for others
  • Lower albumin → more unbound drug → potential for more rapid clearance
• Excretion
  
  • increased RR → more rapid lung excretion
  • Renal flow/GFR increases → shorter half lifes for drugs excreted via renal
  • Drugs that may be affected: nicotine, fluoxetine, citalopram. SSRIs may need increased dose in 3rd tri

Question 3

Nausea tx

mild-moderate

Answer 3

Mild with occational or no vomiting:

• D/C PNV c iron → replace c folic acid supplementation
• Pyridoxine (Vit B6) 25 - 50 mg tid
• Ginger powder/extract 250 mg qid
• P6 acupressire (seabands)

Mild-moderate with mild vomiting (no dehydration)

• Pyridoxine 25 mg bid-tid + doxylamine 12.5 mg bid (or just qHS
• Diclegis up to qid
• If insufficient, add:
  
  • Promethazine (Phenergan) 12.5 - 25 mg OR dimenhydrinate (dramamine) 50 - 100 mg q 4-6 (po or pr)
  • If still insufficient add:
    
    • Reglan 5-10 mg q 8 po or im
    • prochlorperazine (compazine) 5 - 10 q 6-8
    • Phenergan
    • thorazine

Question 4

UTI

Answer 4

Asymtomatic Bacteriuria

• Amoxicillin 250 - 500 mg PO tid x 3-7 days (PCN!)
• Augmentin 250/125mg po qid x 3-7 days (PCN!)
• Cephalexin 500 mg po qid x 5-10 days
• Bactrim po bid 3-7 days
  
  • avoid 1st tri
  • avoid 3rd tri for G6PD defiiciency

Uncomplicated Cystitis - tx x 7 days

• Augmentin qid x 7 days (PCN!)
• Cephalexin 500 mg qid x 7 days
• Nitrofurantoin 100 mg qid x 7 days
• Bactrim po bid x 7 days (sulfa!)
  
  • contra in 1st
  • contra in 3rd for G6PD

Suppression - until end of pregnancy, monthly cx, use 4-6 post partum for pyelo

• Cephalexin 125 - 250 mg po q day
• Nitrofurantoin 100 po qHS

Question 5

Herpes

primary outbreak

Answer 5

Acyclovir 400 mg tid x 7-10 days (or until healed)

Valacyclovir 1 g bid x 7-10 days (or until healed)

Question 6

Herpes

Recurrent Episodes

Answer 6

Acyclovir

• 400 mg tid x 5 days
• 800 mg bid x 5 days

Valacyclovir

• 500 mg bid x 3 days
• 1 g q day x 5 days

Question 7

Herpes

Suppression

Answer 7

Starting at 36 weeks

• Acyclovir 400 mg tid
• Valcyclovir 500 mg bid

Question 8

Preterm birth prevention

Hx spontaneous PTB

Answer 8

17 alpha hydroxyprogesterone caproate (17-OHPC)

250 mg IM q week from 16 - 24 weeks through 36 weeks (or until delivery)

Question 9

Preterm birth prevention

no hx of PTB, but cervical length < 2 cm before 24 wks

Answer 9

Vaginal progesterone gel 90 mg daily per vagina

or

Micronized progesterone gel capsules (200 mg) 1 per vagina daily until 34-37 weeks

Question 10

Hypertensive agents

Answer 10

• Labetalol 100 mg bid → increase by 100 mg bid q 2-3 days prn
  
  • usual dose 200 - 2400 mg/day in divided doses
• Methyldopa 500 - 3000 mg in 2-3 divided doses → increase q 2 days prn
  
  • usual dose 250 - 1000 mg/day in divided doses
• Nifedipine ER 30-120 mg daily → increase q 1-2 weeks prn
  
  • usual dose 30 - 90 mg/day

Question 11

Cholestasis of pregnancy

Answer 11

• Ursodeoxycholoc acid (Actigal)
  
  • 15 mg/kg/day in divided doses (usually 900 mg)
  • natural water-soluable bile acid → interferes with nonsoluable bile → decreased release of pruritic agents
• Cholestyramine (Questran)
  
  • Bile acid sequestrant
  • 8-16 g/day in divided doses
  • give supplemental fat-soluable vitamins and Vit K 10 mg/day
• Benadryl or Vistaril (hydroxazine)
  
  • 25-50 PO q6-8 hours (max 300 mg/day)
  • tx itching not underlying disorder
• Vitamin K 10 mg/day

Question 12

Mastitis treatments

Answer 12

• Dicloxacillin (Dynapen) or Cephalexin (Keflex) 500 mg qid x 10 - 14 days
• If PCN allergic (qid x 10-14 days)
  
  • clindamycin 300 mg
  • erythromycin 250-500 mg

Question 13

Drugs that inhibit breast milk production:

Answer 13

• Alcohol in large amounts
• Bromocriptine (Parlodel)
• Cabergoline (Dostinex)
• Estrogen-containing contraceptives
• Ergotamine
• Progestins
• Pseudoephedrine (Sudafed)
• Testosterone
• Tamoxifen and other estrogen receptor blockers
• Bupropion (Wellbutrin)

Question 14

Drugs to stimulate milk production

Answer 14

Metoclopromide (Reglan) 10-15 mg tid x maximum 1 month

• Side effects: depression, GI side effects, extra-pyramidal sx (rare)