13.2 Prescribing & Drug Interactions

The Dental Practitioners' Formulary

UK dentists prescribe from a restricted list — the Dental Practitioners' Formulary (DPF), contained within the BNF. The DPF covers the antimicrobials, analgesics, sedatives, antifungals, antivirals, and emergency drugs a general dental practitioner may prescribe on an NHS prescription (FP10). Drugs outside the DPF must be prescribed by the patient's medical practitioner; prescribing outside the list risks clawback and regulatory referral.

Writing a Legal Prescription

A valid NHS prescription must include:

• The patient's name, address, and age (date of birth for children).
• The drug (generic name preferred), form, strength, and quantity.
• The dose and frequency (e.g. 'one tablet three times daily').
• The prescriber's name, address, GDC number, signature, and the date.

For controlled drugs used in dentistry (e.g. midazolam is a Schedule 3 CD — exempt from safe custody but invoices must be kept for two years), specific stationery and recording requirements apply.

Prescribing in Special Groups

In pregnancy, defer elective treatment from the first trimester where possible; the second trimester is safest for routine operative work.

Drug Interactions That Matter in Dentistry

These interactions are high-yield for MFDS Part 1 and are commonly tested as scenario stems.

The Warfarin Patient — A Frequent Exam Stem

A patient on warfarin who develops a dental infection is a classic MFDS scenario:

• Do NOT prescribe metronidazole — SDCEP explicitly contraindicates it.
• Do NOT use miconazole oral gel — even topically, enough is swallowed to inhibit CYP2C9; the MHRA has issued a Drug Safety Update on this interaction. Use nystatin for oral candidiasis instead.
• Amoxicillin is usually the safe first choice in penicillin-tolerant patients.
• For analgesia, use paracetamol, not NSAIDs or aspirin.
• Check the INR before surgical treatment (most dentists defer if INR > 4.0 for routine work).

Notes on Common Myths

• Penicillin and the oral contraceptive pill: current Faculty of Sexual and Reproductive Healthcare (FSRH) and MHRA guidance is that additional contraceptive precautions are NOT required with non-enzyme-inducing antibacterials such as amoxicillin or metronidazole. The older 'extra precautions' advice is the classic 'what has changed' wrong option.
• Paracetamol and warfarin: occasional paracetamol at normal doses has no clinically important effect on INR; only prolonged regular use at high doses may modestly raise INR.

Putting It Together

A thorough medical and drug history at every visit is the foundation of safe prescribing. For any patient on warfarin, a DOAC, lithium, methotrexate, or a biological, consult the BNF, check interactions, and liaise with the medical team when the plan is anything other than simple. Document the discussion and your reasoning in the notes.

Controlled Drugs and Record-Keeping

Midazolam, the mainstay of dental conscious sedation, is a Schedule 3 controlled drug: it is exempt from safe-custody requirements but invoices and a controlled-drug register entry must be retained for two years, and prescription requirements apply. Temazepam, now rarely used in dentistry, is also Schedule 3. Dentists do not normally handle Schedule 2 opioids. Every CD prescription must be written in the prescriber’s own handwriting (or a computer-generated form meeting the requirements), with the patient’s full name, address, and date of birth, the drug form and strength, the total quantity in words and figures, the dose, and the prescriber’s signature and GDC number. Keeping an accurate, contemporaneous record is a GDC Standards obligation as well as a legal one; a missing or illegible entry is a common source of complaint and fitness-to-practise referral.