[Table, Practical Considerations for Doxy-PEP Implementation]. - Doxycycline Post-Exposure Prophylaxis to Prevent Bacterial Sexually Transmitted Infections

Table 1: Considerations for Doxy-PEP Implementation
Consideration(s)	Comments
Available formulations	Doxycycline hyclate delayed-release 200 mg oral tablet Doxycycline hyclate or monohydrate immediate-release 100 mg oral capsule or tablet (2 capsules or tablets taken together for a total of 200 mg) The immediate-release formulations are more widely available and usually cost less than the delayed-release formulation.
Administration	As doxy-PEP, 200 mg of doxycycline should ideally be taken within 24 hours after condomless sex, up to 72 hours maximum. No more than 200 mg of doxycycline should be taken in a 24-hour period. Milk and vitamins containing positive cations (e.g., calcium, zinc, magnesium) should be avoided within 2 hours of taking doxycycline, because these interfere with doxycycline absorption and may lower doxycycline levels, potentially reducing efficacy.
Contraindications, drug-drug interactions, and dose adjustments	Doxy-PEP should not be used concurrently with other doxycycline therapy (or any other tetracycline-class antibiotic) for treatment or prevention of a health condition (e.g., acne, rosacea, malaria prophylaxis). No significant drug-drug interactions exist between doxycycline and ARVs used for HIV treatment or PrEP. No known drug reactions exist between doxycycline and gender-affirming hormone therapies. No doxycycline dose adjustments are indicated for patients with renal dysfunction. Doxycycline is generally contraindicated during pregnancy because of potential adverse effects on the fetus [FDA 2016].
Adverse effects	GI adverse effects are common; taking doxycycline with food may help alleviate nausea or GI upset. Symptoms including nausea, vomiting, and reflux can be severe enough to require cessation of doxycycline. Esophageal injury and irritation can occur. Doxycycline should be taken with an 8-oz glass of water and the individual should remain upright for 30 minutes to 1 hour after dosing. Skin photosensitivity and phototoxicity can occur; wearing sunscreen, limiting sun exposure, and avoiding tanning beds can help prevent sunburn and other skin injury. Intracranial hypertension is a rare but serious adverse effect. Refractory headaches or vision changes should be evaluated promptly by a clinician. Doxycycline use may select for antibiotic-resistant organisms, which can cause infections in some circumstances and can disrupt the microbiome.
Supply of doxy-PEP medications	A 30- to 90-day supply is recommended, with actual number of pills to be determined by anticipated or actual dosing frequency during that time (see dose quantity below). Dose quantity: For delayed-release doxycycline 200 mg tablets, the quantity dispensed should not exceed 90 doses per 3 months. For immediate-release 100 mg capsules or tablets, the quantity dispensed should not exceed 180 doses per 3 months. The quantities above are the maximum number to be dispensed; many patients will not need such a large quantity. Shared decision-making can determine the lowest quantity needed based on the frequency of condomless sexual encounters during the prescribing interval.
Follow-up and laboratory monitoring	Engage patients taking doxy-PEP in ongoing comprehensive sexual health services that include STI screening, HIV PrEP, immunizations, and other health promotion strategies as indicated [a]. At least every 3 months: Screen for syphilis, HIV if not previously diagnosed, gonorrhea, and chlamydia (including extragenital testing when indicated), ensuring that tests have been obtained before providing a doxy-PEP prescription refill. Screen for hepatitis B virus at initiation, and screen for hepatitis C virus at least annually [CDC(a) 2024]. Offer HIV PrEP or HIV treatment as needed. Assess for ongoing doxy-PEP needs and continue in shared decision-making as new evidence becomes available. The doxycycline package insert advises periodic monitoring of hepatic function, renal function (specifically BUN), and CBC with prolonged therapy. Such monitoring may not be necessary with intermittent dosing.
Key points for patient education	Medication administration instructions and contraindications: See above. Protective effect: Doxy-PEP is not 100% effective and is not effective against all STIs. For cisgender men and transgender women at risk of STIs who were engaged in routine sexual healthcare, doxy-PEP reduced the likelihood of an STI diagnosis by >50% [Luetkemeyer, et al. 2023]. Evaluation by a clinician after a possible STI exposure is necessary to determine whether treatment is needed. Adverse effects: Doxycycline can cause GI adverse effects, photosensitivity, and esophageal irritation, which can be mitigated using strategies noted above. Long-term doxycycline use may increase the risk of developing an antibiotic-resistant infection. The potential long-term effects of doxy-PEP use are not known at this time. Ongoing screening: Screening for STIs every 3 months is necessary while taking doxy-PEP. Routine HIV testing should continue in individuals at risk of HIV.

Table 1: Considerations for Doxy-PEP Implementation

Consideration(s)

Comments

Available formulations

Doxycycline hyclate delayed-release 200 mg oral tablet
Doxycycline hyclate or monohydrate immediate-release 100 mg oral capsule or tablet (2 capsules or tablets taken together for a total of 200 mg)
The immediate-release formulations are more widely available and usually cost less than the delayed-release formulation.

Administration

As doxy-PEP, 200 mg of doxycycline should ideally be taken within 24 hours after condomless sex, up to 72 hours maximum.
No more than 200 mg of doxycycline should be taken in a 24-hour period.
Milk and vitamins containing positive cations (e.g., calcium, zinc, magnesium) should be avoided within 2 hours of taking doxycycline, because these interfere with doxycycline absorption and may lower doxycycline levels, potentially reducing efficacy.

Contraindications, drug-drug interactions, and dose adjustments

Doxy-PEP should not be used concurrently with other doxycycline therapy (or any other tetracycline-class antibiotic) for treatment or prevention of a health condition (e.g., acne, rosacea, malaria prophylaxis).
No significant drug-drug interactions exist between doxycycline and ARVs used for HIV treatment or PrEP.
No known drug reactions exist between doxycycline and gender-affirming hormone therapies.
No doxycycline dose adjustments are indicated for patients with renal dysfunction.
Doxycycline is generally contraindicated during pregnancy because of potential adverse effects on the fetus [FDA 2016].

Adverse effects

GI adverse effects are common; taking doxycycline with food may help alleviate nausea or GI upset. Symptoms including nausea, vomiting, and reflux can be severe enough to require cessation of doxycycline.
Esophageal injury and irritation can occur. Doxycycline should be taken with an 8-oz glass of water and the individual should remain upright for 30 minutes to 1 hour after dosing.
Skin photosensitivity and phototoxicity can occur; wearing sunscreen, limiting sun exposure, and avoiding tanning beds can help prevent sunburn and other skin injury.
Intracranial hypertension is a rare but serious adverse effect. Refractory headaches or vision changes should be evaluated promptly by a clinician.
Doxycycline use may select for antibiotic-resistant organisms, which can cause infections in some circumstances and can disrupt the microbiome.

Supply of doxy-PEP medications

A 30- to 90-day supply is recommended, with actual number of pills to be determined by anticipated or actual dosing frequency during that time (see dose quantity below).
Dose quantity:
- For delayed-release doxycycline 200 mg tablets, the quantity dispensed should not exceed 90 doses per 3 months.
- For immediate-release 100 mg capsules or tablets, the quantity dispensed should not exceed 180 doses per 3 months.
- The quantities above are the maximum number to be dispensed; many patients will not need such a large quantity. Shared decision-making can determine the lowest quantity needed based on the frequency of condomless sexual encounters during the prescribing interval.

Follow-up and laboratory monitoring

Engage patients taking doxy-PEP in ongoing comprehensive sexual health services that include STI screening, HIV PrEP, immunizations, and other health promotion strategies as indicated [a].
At least every 3 months:
- Screen for syphilis, HIV if not previously diagnosed, gonorrhea, and chlamydia (including extragenital testing when indicated), ensuring that tests have been obtained before providing a doxy-PEP prescription refill.
- Screen for hepatitis B virus at initiation, and screen for hepatitis C virus at least annually [CDC(a) 2024].
- Offer HIV PrEP or HIV treatment as needed.
- Assess for ongoing doxy-PEP needs and continue in shared decision-making as new evidence becomes available.
The doxycycline package insert advises periodic monitoring of hepatic function, renal function (specifically BUN), and CBC with prolonged therapy. Such monitoring may not be necessary with intermittent dosing.

Key points for patient education

Medication administration instructions and contraindications: See above.
Protective effect: Doxy-PEP is not 100% effective and is not effective against all STIs. For cisgender men and transgender women at risk of STIs who were engaged in routine sexual healthcare, doxy-PEP reduced the likelihood of an STI diagnosis by >50% [Luetkemeyer, et al. 2023]. Evaluation by a clinician after a possible STI exposure is necessary to determine whether treatment is needed.
Adverse effects: Doxycycline can cause GI adverse effects, photosensitivity, and esophageal irritation, which can be mitigated using strategies noted above. Long-term doxycycline use may increase the risk of developing an antibiotic-resistant infection. The potential long-term effects of doxy-PEP use are not known at this time.
Ongoing screening: Screening for STIs every 3 months is necessary while taking doxy-PEP. Routine HIV testing should continue in individuals at risk of HIV.

From: Doxycycline Post-Exposure Prophylaxis to Prevent Bacterial Sexually Transmitted Infections

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