The diet of patients with reduced tryptophan serum levels that are either hospitalized for acute respiratory infection or treated for chronic inflammatory diseases such as inflammatory bowel diseases (in- or outpatients) is supplemented with controlled-ileocolonic-release nicotinamide (CICR-NAM) at doses of 500 mg or 1000 mg per day for four weeks. In the COVit-2 trial (NCT04751604), nicotinamide supplementation including CICR-NAM has been shown to accelerate physical recovery from mild-to-moderate COVID-19 (for publication, see References). The main objective of this open-label case series is to investigate the pharmacokinetics and metabolism of nicotinamide in patients with more severe respiratory infections or chronic inflammatory conditions. In addition, patients can optionally provide information on their quality of life and fatigue status.

Inclusion Criteria:

• Serum tryptophan levels below normal range.
• Acute, infectious respiratory disease requiring treatment (e.g. proven acute SARS-CoV-2 or influenza virus infection with inpatient treatment) or chronic inflammatory disease (e.g. chronic inflammatory bowel disease) in remission or in acute relapse (outpatient or inpatient treatment).

Exclusion Criteria:

• Inability to give informed consent.
• Pregnancy or breastfeeding.
• Serious other illness, e.g. cancer.
• Anemia: Hb <10 mg/dL.
• Intake of medication to raise the pH value in the stomach (e.g. proton pump inhibitors, H2 receptor antagonists or antacids) in higher doses over a longer period of time.

Specific requests by academic researchers can be addressed to the principal investigators. On the basis of such a request including a detailed analysis plan, access might be provided, subject to a decision of the Ethics Committee of the Medical Faculty of Kiel University to ensure compliance with privacy laws, data protection and requirements for consent and anonymization.