Pharmaceutical factors affecting drug bioavailability

What is pharmacokinetics?

What body does to drug - ADME
Absorption

Distribution

Metabolism

Excretion

What is bioavailability (F)?

Fraction of orally administered drug absorbed into systemic circulation

F = (AUC oral)/(AUC IV)

Name 3 drugs that shouldn’t be swapped because of pharmacokinetics

Carbamazepine - antiepileptic

Lithium - bipolar

Ciclosporin - immunosuppressant

What are MR/SR drugs used for? (2)

Reduce rate of absorption

Deliver drug to specific region of GI tract

What are the 2 types of morphine for different pain relief?

Oramorph- oral suspension for immediate pain relief

Morphogesic SR - SR tablet for 12 hourly pain relief

What is nifedipine?

DHP calcium channel blocker used in HT and angina

Rapid onset, short duration

Why is omeprazole mostly given as enteric coated?

It’s acid labile

What is omeprazole used for? (4)

1. Indigestion

2. Heartburn

3. Stomach ulcers

4. Zollinger-Ellison syndrome

How does omeprazole work?

Activates at acidic pH

Inhibits PPs in parietal cells

Degrades at pH 5-6

Why are skin patches used and name 2 types?

For SR

Glyceryl trinitrate and fentanyl(replace oral morphine)

Give 3 reasons a patient might not be able to swallow

Stroke - administer via NG-tube/IV line

Severe infection - IV antibiotics

Palliative care - fentanyl patches, diamorphine via syringe driver

What are depot injections?

Deep IM

• used to aid compliance with injections weekly/ monthly

• absorption by use of thick oils that slow down rate of diffusion from injection site

• avoids first pass metabolism

Name 2 examples of depot injections

Norethisterone enanthate in oil (contraception) every 8 weeks

Fluphenazine decanoate in oil (schizophrenia)

Percentage solutions

100% = 100 g per 100 mL or 10 g per 10 mL or 1g per mL

 10% = 10 g per 100 ml or 1 g per 10 mL or 100 mg per mL

  1% = 1 g per 100 mL or 100 mg per 10 mL or 10 mg per mL

  0.1% = 100 mg per 100 mL or 10 mg per 10 mL or 1 mg per mL

What is 0.1mg in mcg?

100mcg