Skip to content

Doxycycline

Overview

Field Detail
Drug class Tetracycline antibiotic
Stock formulation 100 mg powder for injection or 100 mg tablets
Reconstituted conc. 10 mg/mL (add 10 mL WFI)
Storage Room temp before reconstitution; Protect from light

Preparation (IV Testing)

Reconstitution

Wait for the powder to dissolve completely. The solution should be clear and yellow. Prepare IDT dilutions immediately after reconstitution.

Equipment needed

  • 1 × Doxycycline 100 mg powder vial
  • Water for Injections (WFI) or Normal saline (NS) — for reconstitution
  • Normal saline (NS) — for IDT dilutions
  • 10 mL syringe
  • 1 mL syringes × 4 (for test doses/dilutions)
  • 25 G needles

Step 1 — Reconstitute the stock (10 mg/mL)

  1. Add 10 mL of WFI or NS to the 100 mg powder vial.
  2. Shake gently until completely dissolved. (This is 10 mg/mL).
  3. Draw up 0.5–1 mL into a 1 mL syringe.
  4. Label: "Doxycycline SPT 10 mg/mL".

Step 2 — Prepare IDT dilutions

Prepare in this order, using a fresh syringe for each step.

  1. IDT 1 mg/mL (1:10):

    • Draw 0.1 mL of stock (10 mg/mL) into a 1 mL syringe. Add 0.9 mL NS. Mix. (This is 1 mg/mL — 1:10).
    • Label: "Doxycycline IDT 1 mg/mL".

  2. IDT 0.1 mg/mL (1:100):

    • Draw 0.1 mL of the 1 mg/mL syringe into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.1 mg/mL — 1:100).
    • Label: "Doxycycline IDT 0.1 mg/mL".

  3. IDT 0.01 mg/mL (1:1,000):

    • Draw 0.1 mL of the 0.1 mg/mL syringe into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.01 mg/mL — 1:1,000).
    • Label: "Doxycycline IDT 0.01 mg/mL".

  4. IDT 0.001 mg/mL (1:10,000):

    • Draw 0.1 mL of the 0.01 mg/mL syringe into a new 1 mL syringe. Add 0.9 mL NS. Mix. (This is 0.001 mg/mL — 1:10,000).
    • Label: "Doxycycline IDT 0.001 mg/mL".

Skin prick test (SPT)

Reagent Concentration
Test solution Neat (10 mg/mL)
Positive control Histamine 10 mg/mL
Negative control Normal saline

Interpretation: Wheal ≥3 mm vs negative control = positive.

Intradermal test (IDT)

Dilution series

Step Dilution Concentration Preparation
1 1:10,000 0.001 mg/mL 0.1 mL of 0.01 mg/mL + 0.9 mL NS
2 1:1,000 0.01 mg/mL 0.1 mL of 0.1 mg/mL + 0.9 mL NS
3 1:100 0.1 mg/mL 0.1 mL of 1 mg/mL + 0.9 mL NS
4 1:10 1 mg/mL 0.1 mL neat + 0.9 mL NS

Inject: 0.05 mL intradermal. Read at 15–20 minutes.

Oral Graded Challenge (OGC)

Using APO-Doxycycline 100 mg tablets.

Protocol

Step Dose Formulation Cumulative Dose
1 25 mg 1/4 Tablet 25 mg
2 50 mg 1/2 Tablet 75 mg
3 100 mg 1 Tablet 175 mg

Interval: 30–60 minutes between steps.